摘要:

Journal of Materials Chemistry Scientific Advisory Editor Professor Martin R. Bryce Department of Chemistry University of Durham South Road Durham DH1 3LE, UK Associate Editor Professor Jean Etourneau ICMCB Avenue du Docteur Schweitzer 33600 Pessac France Editorial board Allan E. Underhill (Chairman) Bangor Peter G. Bruce St. Andrews Martin R. Bryce Durham Jean Etourneau Bordeaux Managing Editor Janet L. Dean Deputy Editor Zoe G. Lewin Assist ant Edit or Graham F. McCann Editorial Secretary Miss D. J. Halls Wendy R. Flavell UMIST John W. Goodby Hull Klaus Praefcke Berlin Brian J. Tighe Aston International advisory editorial board K. Bechgaard Ris0, Denmark J. Y. Becker Beer-Sheva, Israel A. J. Bruce Murray Hill, USA E.Chiellini Pisa, Italy D. Coates Poole, UK P. Day London, UK D. A. Dunmur Shefield, UK B. Dunn Los Angeles, USA W. J. Feast Durham, UK R. H. Friend Cambridge, UK A. Fukuda Tokyo, Japan D. Gatteschi Florence, Italy P. Hodge Manchester, UK Information for authors The Royal Society of Chemistry welcomes submission of manuscripts intended for publication in two forms, Articles and Materials Chemistry Communications. These should describe original work of high quality dealing with the synthesis, structures, properties and applications of materials, particularly those associated with advanced technology. Full papers contain original scientific work that has not been published previously. However, work that has appeared in print in a short form such as a Materials Chemistry Communication is normally acceptable.Four copies of Articles including a top copy with figures etc. should be sent to the Managing Editor at the Cambridge address. Journal of Materials Chemistry (ISSN 0959-9428) is published monthly by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK. All orders accompanied with payment should be sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road, Letchworth, Herts SG6 lHN, UK. NB Turpin Distribution Services Ltd., distributors, is wholly owned by The Royal Society of Chemistry. 1996 Annual subscription rate EEA (incl. UK) fS19.00, USA $934.00, Rest of World E532.00.Customers A. B. Holmes Cambridge, UK H. Inokuchi Okazaki, Japan W. Jeitschko Munster, Germany 0. Kahn Bordeaux, France J. Livage Paris, France R. McCullough Pittsburgh, USA J. S. Miller Salt Lake City, USA K. Miillen Mainz, Germany L. Niinisto Espoo, Finland M. Nygren Stockholm, Sweden Y. W. Park Seoul, Korea N. PlatC Moscow, Russia Materials Chemistry Communications contain novel scientific work in short form and of such importance that rapid publication is warranted. The total length is normally restricted to two printed A4 pages. However, special consideration will be given to communications with a large amount of essential diagrammatic information. Submission of a Materials Chemistry Communication can be made either to the Managing Editor at the Cambridge address, or via a member of the International Advisory Editorial Board.In the latter case, the top copy of the manuscript including any figures etc., together with the name of the person to whom the Communication is being submitted, should be sent simultaneously to the Managing Editor at the Cambridge address. All authors submitting work for publication are should make payments by cheque in sterling payable on a UK clearing bank or in US dollars payable on a US clearing bank. Air freight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. USA POSTMASTER: send address changes to Journal of Materials Chemistry, Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003.Periodicals postage paid at Jamaica, NY 11431. All other dispatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. Editorial Production Coordinator Stephanie Shah Technical Editors Carole J. Nerney Alan J. Holder Jeff R. White Graphics Designer Ms C. Taylor-Reid Anthony R. West Aberdeen John D. Wright Canterbury Janet L. Dean (Secretary) M. Prato Trieste, Italy C. N. R. Rao Bangalore, India B. Raveau Caen, France T. Rojo Bilbao, Spain J. Rouxel Nantes, France A. Simon Stuttgart, Germany M. A. Subramanian Wilmington, USA S. Takahashi Osaka, Japan J. 0.Thomas Uppsala, Sweden M. Vallet-Regi Madrid, Spain D.E. W. Vaughan Annandale, USA Y. Yamashita Okazaki, Japan required to sign an exclusive copyright licence. All submissions should be accompanied by a completed form (a blank for photocopying is reproduced at the end of the Information for Authors in Issue l), without which publication cannot proceed. A completed graphical abstract template should also accompany each submission. Full details of the form of manuscripts for Articles and Materials Chemistry Communications, conditions for acceptance etc. are given in Issue 1 of Journal of Materials Chemistry published in January of each year, on the world wide web (htpp://chemistry.rsc.org/rsc/)or may be obtained from the Managing Editor. There is no page charge for papers published in Journal of Materials Chemistry. Fifty reprints are supplied free of charge. Janet L. Dean, Managing Editor Tel.: Cambridge (01223) 420066 E-Mail (INTERNET): DEANJ@RSC.ORG Fax: (01223) 420247 Advertisement sales: Tel. +44 (0)171-287 3091; Fax +44 (0)171-494 1134 0The Royal Society of Chemistry, 1996. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers.

ISSN:0959-9428    

DOI:10.1039/JM99606FX029

出版商:RSC    

年代:1996

数据来源: RSC

ISSN:0959-9428    

DOI:10.1039/JM99606BX031

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

ISSN 0959-9428 JMACEP(9) 1455-1604 (1996) Synthesis, structures, properties and applications of materials, particularly those associated with advanced technology cn CONTENTS Articles 1455 Nitrodisplacement reactions and the synthesis of bis(ether anhydride)s from dihydrox ynaphthalenes Geoffrey C.Eastmond and Jerzy Paprotny I 'bO-Nap-O'@ HOzC0 I V JV 1459 Synthesis and properties of poly(ether imide)s derived from dihydroxynaphthalenes 1"Geoffrey C.Eastmond and Jerzy Paprotny 1465 Ferrocene-containing thermotropic liquid crystals: laterally connected twins Jens Andersch, Siegmar Diele and Carsten 0+==Tschierske 1 O 0'p / 1469 Thermal and optical properties of chiral twin liquid crystalline bis(cholestery1) alkanedioates Antonius T.M. Marcelis, Arie Koudijs and Ernst J. R. Sudholter 1473 Linear precursors of liquid crystalline thermosets Barbara Him, Cosimo Carfagna and Rosa Lanzetta 1479 Liquid crystal polymers copolymers and elastomers containing a laterally attached mesogenic unit Eric A. Whale, Frederick J. Davis and Geoffrey R. Mitchell 1487 Two-step refractive index changes by photoisomerization and photobleaching processes in the fdms of non-linear optical polyurethanes and a urethane-urea copolymer Osamu Watanabe, Masaaki Tsuchimori and Akane Okada 1493 Second-order non-linear optical properties of Langmuir-Blodgett films of a new azo compound (p-N02)C6H,N=NClo&0 (CH2)3N (CH,)&H,,Br and its europium complex W. S.Xia, C. H. Huang, T. R. Cheng, L. B. Gan, X. S. Zhao and A. C. Yu 1497 Zinc sulfide thin films grown by SILAR on poly (vinyl chloride) and polycarbonate substrates Seppo Lindroos, Tapio Kanniainen and Markku Leskela 1501 Thermal decomposition of V(NFA2), in an MOCVD reactor: a low-temperature route to vanadium carbonitride coatings Pierre Bonnefond, Roselyne Feurer, Alex Reynes, Francis Maury, Benoit Chansou, Robert Choukroun and Patrick Cassoux kl k2 T-state C-state -S-state k-1 11 1507 Thin film deposition of Ge,C,,H, by radiolysis of GeH,-C,H, mixtures Paola Benzi, Mario Castiglioni, Enrico Truffa and Paolo Volpe 15 1 1 Investigations on the charge transport in r,----I5O LaMnO, +6 at low temperatures Jorg Topfer, Jean-Pierre Doumerc and Jean-Claude Grenier 0 I00 200 100 TIK Y.Laureiro, E. Moran, R. Rojas and M. A. Alario-Franco A undoped-YBCO 1521 Two-dimensional molecular-based ferrimagnets incorporating decamethylmetallocenium cations Yu Pei, Scott S. Turner, Lkopold Fournes, Joel S. Miller and Olivier Kahn 1527 A new solution route to silicates. Part 4.- submicronic zircon powders Alain Mosset, Pierre Baules, Pierre Lecante, Jean-Christian Trombe, Hamid Ahamdane and Faouzi Bensamka 1533 Stoichiometry, structures and polymorphism of .-\-. --.--\spinel-like phases, Lil.,3xZn2-2,Til + 0.6,x04 lMli=12M)Virginia Santos Hernandez, Leticia M. Torres P Martinez, Glenn C. Mather and Anthony R. West 'IBM) ...111 1537 Formation mechanism of a crystalline Ag,J’&, solid solution by impact ball-materials interaction Luc Aymard, Bernard Beaudoin, Bernard Dumont and Agnes Delahaye-Vidal 1543 Influence of size and shape of metallic silver and palladium powders on the Ag,,,Pd,o solid solution formation by mechanical alloying Luc Aymard, Bernard Dumont, Bernard Beaudoin and FranCois Portemer 1549 Evidence of new layered cuprates in the Hg-A-Gd-Cu-0 system (A =Ba, Sr) A. Sundaresan, Denis Pelloquin, Antoine Maignan, Maryvonne Hervieu, Claude Michel, U. V. Varadaraju and Bernard Raveau 1557 Dehydration-rehydration in magnesium vermiculite: conversion from two-one and one-two water layer hydration states through the formation of interstratified phases Antonio Ruiz-Conde, Antonio Ruiz-Amil, Jos6 L.Perez-Rodriguez and Pedro J. Sanchez-Soto 1567 The reversible extraction of the hexamminecobalt(ru) cation by kanemite (NaHSi,O, 3H20): enhanced extraction in the presence of a cationic surfactant Matthew T. J. Keene, James A. Knowles and Michael J. Hudson 1575 Stabilisationof Ba,CuO,Cl, with the K2NiF4 structure by chemical substitution Thomas Kodenkandath, Gianluca Calestani and Francesco C. Matacotta Pd 0 0 0 0 iv 1579 A combined time-of-flight powder neutron and powder X-ray diffraction study of ternary chromium sulfides, V,Cr, -xS4(0 <x <1.0) Douglas C. Colgan and Anthony V. Powell 1585 Structure and magnetotransport properties of the layered manganites RE1.2Sr1.8Mn207 (RE =La, Pr, Nd) Ram Seshadri, Christine Martin, Antoine Maignan, Maryvonne Hervieu, Bernard Raveau and C.N. Ramachandra Rao -2 .1591 Low-temperature synthesis and I electrochemical lithium intercalation behaviour of defect Li-Mn-0 spinel oxide Pierre Strobel, Susanne Rohs and Frederic Le Cras ioo 200 300 400 500 T/"C 1595 Characterization of heterogeneous structure in a polymer object manufactured by stereolithography with low-frequency microechography L. Simonin, S. Zissi, J. P. Gonnet, J. J. Hunsinger, S. Corbel and D. J. Lougnot 160 Solution of an organic crystal structure from X-ray powder diffraction data by a generalized rigid-body Monte Carlo method: crystal structure determination of 1-methylfluorene Maryjane Tremayne, Benson M.Kariuki and Kenneth D. M. Harris 12 14 i Cumulative Author Index iv Conference Diary Note: Where an asterisk appears against the name of one or more authors, it is included with the authors' approval to indicate that correspondence may be addressed to this person. COPIES OF CITED ARTICLES The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact: The Library, Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN, UK. Tel: +44 (0)171-437 8656, Fax: +44 (0)171-287 9798, Telecom Gold 84: BUR210, Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society's Library, the staff will be pleased to advise on its availability from other sources.Please note that copies are not available from the RSC at Thomas Graham House, Cambridge. V BRITISH LIQUID CRYSTAL SOCIETY ONE DAY SYMPOSIUM -December 16th 1996 "CHALLENGES AHEAD IN SURFACTANT LIQUID CRYSTALS" AT UNILEVER RESEARCH PORT SUNLIGHT LABORATORY Invited Speakers: H Wennerstrom (Lund, Sweden) H Finkelmann (Freiburg, Germany) J Lydon (Leeds, UK) J Penfold (Rutherford CLRC lab, UK) J Seddon (London, UK) P Warren (Port Sunlight, UK) Sponsored by Unilever Research to mark the retirement of Professor G J T Tiddy. For further details contact: Dr I Howell or Dr P B Warren at: Unilever Research Port Sunlight Laboratory Quarry Road East Bebington Wirral Mersey side L63 3JW, UK Tel: 0151 471 340713812 Fax: 0151 471 812 E-mail: patrick.warren 0unilever.com or: ian.howel1 @unilever.com Also: Professor D W Bruce Department of Chemistry University of Exeter EXETER EX4 4QD Tel: 01392 263489 Fax: 01392 263434 E-mail: d.bruce 0exeter. ac.uk

ISSN:0959-9428    

DOI:10.1039/JM99606FP073

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Cumulative Author Index 1996 Abe J., 711 Agranat I., 11 19 Ahamdane H., 1527 Alario-Franco M. A., Albiston L., 871 1517 Boyle D. S., 227 Bradley D. D. C., 1253 Branger C., 555 Bravic G., 5 Breen C., 253, 849 Damiani D. E., 1433 DAndrea G., 585 Dann A. J., 1361 Daolio S., 567 Daturi M., 879 Fujimoto H., 1361 Fukuda A., 671, 753 Furukawa T., 1231 Gachard E., 867 Gallardo Amores J. M., 879 Hinklin T. R., 1441 Hiraoki T., 727 Hirn B., 1473 Hitch T. J. A. R., Hiyama T., 753 285 Alcantara-Rodriguez M., 247 Ali F., 261 Ali-Adib Z., 15 Allen J. L., 165, 1141 Allen K. M., 1445 Almond G. G., 843 Alonso P. J., 533 Al-Raihani H., 495 Amari C., 1319 Amarilla M. J., 1005 Andersch J., 1297, 1465 Ando I., 719 Brendel U., 271 Brettle R., 747 Britton D., 123 Brooks J. S., 849 Brouca-Cabarrecq C., 789 Brown C.R., 23, 969 Brown I. W. M., 1225 Bruque S., 639 Bryce M. R., 699, 903 Budd P. M., 1099 Budig H., 1283 Buist G. J., 911 Bukhtenko 0.V., 207 Davies A., 49 Davies T. W., 73 Davis F., 15 Davis F. J., 1479 Davis S. J., 479 Davison C. M., 1187 Dawson D. H., 409 de Lacy Costello B. P. J., 289 Delahaye-Vidal A., 1537 Delmas C., 193 de Souza D. P. F., 233 de Souza M. F., 233 Gan L. B., 1493 Ganguli M., 391 Gao Q., 1207 Gao Y., 369 Garcia J. R., 415 Garcia-Granda S., 415 Gay D. H., 653 Gazzoli D., 403 Geise H. J., 559, 1325 Gentle I. R., 137, 969 George C. D., 131 Gerdanian P., 619 Gibb T. C., 1187 Hobson R. J., 49 Hodge P., 15, 375, 527 Hoffmann R-D., 429 Ho-Hoang A,, 1107 Holloway A,, 629 Holloway J., 221 Holmberg S., 1309 Holmes P.A., 539 Honeybourne C. L., 277, 285,289, 323 Horita K., 795 Howie R.A., 1379 Howlin B. J., 305, 311, 911 Andreozzi G. B., 987 Andrews S. R., 539 Antonietta Massucci M., 645 Apperley D. C., 1031 Arai H., 455 Arai K., 11 Burggraaf A. J., 815 Burn P. L., 1253 Busca G., 879 Bush T. S., 395 Bushnell-Wye G., 337,449 Byrn S. R., 123 Cabeza A., 639 Destri S., 1319 Diaz L., 975 Dickens P. G., 1211 Diele S., 1087, 1283, 1297, Dirken P. J., 337 Dixit M., 1429 1465 Gibson I. R., 895 Gilbart E., 1175 Glenis S., 1 Glidle A., 1259 Gogotsi Y. G., 595 Goldenberg L. M., 699 GomiY., 119 HuZ., 1041 Huang C. H., 1493 Huang J. L., 1131 Huang K-S., 123 Hudson M. J., 49, 89, 1567 HulinskL V., 975 Humberstone P., 315 Aranda M. A. G., 639 Arc0 M. d., 1419 Cabrera S., 175 Cai S.X., 1249 Domingues-Rodrigues A., 207 Goiii A., 421 Gonnet J. P., 1595 Hunsinger J. J., 1595 Huve M., 1339 Ariza E., 1059 Arriortua M. I., 421 Ashwell G. J., 23, 131, 137, 969 Caldts M. T., 175 Calestani G., 1575 Calleja R. D., 547 Calvert P., 1157 Dommisse R., 559, 1325 Dotze M., 547 Dou Y., 1369 Doumerc J.-P., 1511 Gonsalves K. E., 1407 Goodby J. W., 919, 1271 Gorbenko 0. Y., 623 Gordon J., 1253 Hyde T., 1379 Igarashi C., 953 Ihanus J., 161, 983 Iimura N., 671 Attfield J. P., 57 Aymard L., 1537, 1543 Bach S., 1149 Baena M. J., 1291 Baert F., 1123 Baffier N., 1149 Bahloul-Hourlier D., 595 Cameron N. R., 719 Campbell S. A., 295 Campillos E., 349, 533 Campostrini R., 585 Carfagna C., 1473 Carleer R., 559, 1325 Carroll S., 559, 1325 Dragone R., 403 DuY., 1239 Dubois J., 1395 Dumont B., 1537, 1543 Dunmur D.A., 747,919 Durand B., 495 Dusastre V., 1351 Gore J. G., 201, 1375 Gozzi D., 987 Graboy I. E., 623 Graham P., 843 Green D. A., 449 GrCgoire G., 1149 Grenier J.-C., 1511 Ikemoto I., 501 Imae I., 117 Ingram-Jones V. J., 73 Inman D., 495, 1239 Inoue H., 455 Inoue M., 1157 Inui S., 671 Bahra G. S., 23, 969 Banister A. J., 1161 Carturan G., 585 Casal B., 1005 Dussack L. L., 81 Duvauchelle N., 573 Grijalva H., 1157 Grobelna B., 579 Irvine J. T. S., 895 Ishikawa T., 1401 Baraton M.-I., 1407 Cassoux P., 1501 Eadon D., 221, 1379 Grobet P., 239 Isozaki T., 753 Barberis G. E., 421 Barcina J. O., 957 Castiglioni M., 1507 Catlow C. R. A., 653 Eastmond G. C., Eckert H., 801 1455,1459 Grozdanov I.S., 761 Gulino A., 1335 Itaya A., 705 Iwane H., 671 Barclay G. G., Bardosova M., 905 375 Caurant D., Ceccato R., 1149 585 Egdell R. G., 1369 Eguchi K., 455 GunBer W., 547 GUO L-H., 369 Iyoda M., 501 Jackson P. D., 137 Barrans Y., 5 Cellucci F., 987 Einsiedel H., 1319 Guzman G., 505 Jacobson A. J., 81 Barrel1 K. J., 323 Cerrini R., 903 Ekstrom T. C., 1225 Haase W., 935 Jakob E., 935 Barriga C., 1199 Barris G. C., 1225 Barton J. M., 305, 911 Barzoukas M., 555 Chakrabarti N., 1169 Chakravorty A. K., 833 Chane-Ching K., 5 Chansou B., 1501 Elhsissen K. T., 573 Ellert 0. G., 207 Enoki T., 119 Enomoto M., 119 Haberle N., 935 Hahn J. H., 365 Hall S. B., 183 Hamada D., 69 Jaleel V. A., 1395 James M., 57 Janes R., 183 Jansson K., 97, 213 Bassoul P., 5 Charters R.B., 131 Esmans E., 1325 Hamer J. C. E., 849 Jarmo Koivusaari K., 449 Bast1 Z., 155, 975 Battisti A. De., 567 Battle P. D., 201, 395, 1187, 1375 Chassagneux F., 495 Chasseau D., 5 Chen C., 765, 815 Chen J., 465 Espinet P., 1291 Etter the late M. C., Eustace P., 527 Evans P., 289, 295 123 Hamerton I., 305, 311 Hamet J-F., 165, 1141 Hamilton D. G., 23 Hamzaoui F., 1123 Jefferies G., 131, 137 Jiang H., 1075 JimCnez-Lbpez E. R-C. A., 247 Baules P., 1527 Chen K., 1041 Ewen R. J., 289 Hanack M., 957 Jones J. R., 305, 911 Baur W. H., 271, 1413 Bay B. H., 331 Bearchell C. A., 1211 Beaudoin B., 1537, 1543 Behrens U., 547 Chen X., 1, 615, 1407 Cheng T. R., 1493 Chiba K., 1235 Chippindale A. M., 611 Chisholm M.S., 527 Ezekwenna P., 1165 Fache F., 1107 Fahy M. R., 1361 Fan Y., 1041 Fantozzi G., 1395 Harding J. H., 653 Harino K., 1241 Harkema S., 357 Harris K. D. M., 1601 Harris R. K., 843, 1031, Joswig W., 1413 Joubert J-C., 1165 Juan A., 1433 Judeinstein P., 51 1 Jumas J-C., 41 Belloni J., 867 Bensamka F., 1527 Choi J. U., 365 Choukroun R., 1501 Farcy J., 37 Farr I. V., 103 Harrison N. M., 1219 1385 Kaczorowski D., 429 Kadokawa J-I., 1235 Benzi P., 1507 Berry F. J., 221 Bertoti I., 1175 Beteille F., 505 Bianchi V., 1149 Bickmore C. R., 1441 Bieniok A., 271 Chung D. D. L., 469 Chung H., 365 Clarkson G. J., 315 Clearfield A,, 639 Clemente D. A., 941 Cohen S., 1119 Cole-Hamilton D. J., 507, Farrand L. D., 747 Fawcett I. D., 1211 Febri M., 1165 FCrey G., 1073 Ferragina C., 645 Feurer R., 1501 Fievet F., 1047 Harrison W.T. A., 81 Hasegawa M., 711 Hasegawa N., 605 Hashimoto S., 753 Hauptman Z. V., 1161 Hayashi H., 459 He H., 1391 Kagawa S., 97 Kahn O., 1521 Kakkar A. K., 1075 Kamath P. V., 1429 Kanamura K., 33 Kandori K., 1401 Kannan T. S., 1395 Bikchantaev I., 733 Blin J. L., 385 Boggavarapu S., 1157 Boiteux G., 1107 Bomben A., 15 Bonnefond P., 1501 Booth C., 1099 Booth C. J., 919, 927 Bornholdt K., 271 Boschi T., 953 Boulanger C., 773 Boutinaud P., 381 Bouwmeester H. J. M., 815 Colgan D. C., 1579 Colley R. A., 1099 Collins D. R., 1385 Condorelli G. G., 1013, Cook M. J., 149, 677 Cooke S., 1 Corbel S., 1595 Cowley A. R., 611 Crayston J. A., 187, 1259 Crespo I., 1199 Dafadar M. H., 833 1259 1335 FiCvet-Vincent F., 1047 Flint S.D., 629 Foran G. J., 969 Forder S., 849 Forester T. R., 1385 Fort A., 555 Foster D. F., 507 Fournes L., 1521 Fragala I. L., 1013, 1335 Franke U., 547 Franklin K. R., 109, 843, Frauenheim T.. 899 871 Heald R. C., 311 Heatley F., 1099 Henshaw G. S., 1351 Hepel M., 993 Heppke G., 927 Hernan L., 37, 861 Hernandez V. S., 1533 Herrera-Urbina R., 573 Hersans R., 149 Hervieu M., 165, 175, 1141, Heyes S. J., 1445 Hillman A. R., 993 1549, 1585 Kanniainen T., 161, 983, Kano S., 1191 Karasu M., 1235 Kariuki B. M., 1601 Katerski A., 377 Kaul A. R., 623 Kawaguchi K., 117 Keana J. F. W., 1249 Keene M. T. J., 1567 Kelder E. M., 765 Kennard C. H. L., Khomenko G. E., 595 1497 23, 137 1 Kikuchi K., 501 Kilian D., 935 Kim J. H., 365 Kim S.B., 365 Kinjo N., 727 Kitazawa T., 119 Klar G., 547 Klinowski J., 1391 Klissurski D. G., 1035 Knowles J., 1135 Knowles J. A., 89, 1567 Kochubey D. I., 207 Maiti H. S., 1169 Maksimov Y. V., 207 Malandrino G., 1013 Malet P., 1419 Mancini N. A., 1013 Mann B. E., 253 Manthiram A., 999 Marcelis A. T. M., 1469 Marcos M., 349, 533 Mariappan L., 1395 Marrot B., 789 Marson C. M., 747 Ogata H. T. S., 1235 Ogawa K., 143 Ohashi M., 1191 Ohwaki K., 795 Ohyama T., 11 Oka Y., 1195 Okada A., 1487 Olbrich F., 547 Olivera-Pastor P., 247 Olivier-Fourcade J., 41 Omenat A,, 349 Oh N-K., 1079 Rodriguez-Castellon E., 247 Rohl A. L., 653 Rohs S., 1591 Rojas R., 1517 Rojo T., 421 Ros M. B., 1291 Rosseinsky M. J., 1445 Ruiz-Amil A., 1557 Ruiz-Conde A., 1557 Ruiz-Hitzky E., 1005 Russell D.A., 149 Saadoune I., 193 Suzuki T., 671 Suzuki Y-i., 753 Szepvolgyi J., 1175 Szydiowska J., 733 Tagliatesta P., 953 Tai Z., 963 Takahashi H., 795 Takahashi M., 119 Takanishi Y., 671, 753 Takashima M., 795 Takeda H., 1055 Takeda M., 119 Kodenkandath T., 1575 Martin C., 1245, 1585 Oriakhi C. O., 103 Sadaoka Y., 953, 1355 Takehara Z-I., 33 Koehler K., 579 Kooli F., 1199 Koroglu A., 1031 Koto K., 459 Koudijs A., 1469 Koyama S., 1055 Kremer R. K., 635 Kreuzer F-H., 935 Kristof J., 567 Krowczynski A., 733 Kruerke D., 927 Martinez E. S., 547 Martinez J. I., 533 Marucci A., 403 Marugan M. M., 667 Marzotto A., 941 Matacotta F. C., 1575 Mather G. C., 1379, 1533 MatijeviC E., 443 Matsui M., 1113 Matsuyama H., 501 Mattei G., 403 Orpen G. A., 993 Ostrovski D., 1309 Otterstedt J-E., 213 Ouchi S., 1401 Ouyang J-m., 963 Pac C., 143 Pagura C., 567 Panda P.K., 1395 Paprotny J., 1455, 1459 Parent C., 381 Park J. W., 365 Saeed T., 1135 Saito K., 501 Saito Y., 1055 Sakamoto M., 1355 Sakata Y., 1241 Salvado M. A,, 415 Salvador S., 73 Samoylenkov S. V., 623 Sanchez C., 511 Sanchez Escribano V., 879 Sanchez L., 37, 861 Takezoe H., 753, 1231 Tamaki S., 1191 Tamaura Y., 605 Tanaka K., 953 Tanaka M., 459 Tang W., 963 Tatam R. P., 131 Taylor R., 155 Teare G. C., 301 ten Elshof J. E., 815 Tendeloo G. V., 1339 Kruidhof H., 815 Kudnig J., 547 Kuroda K., 69, 1055 Kurosu H., 719 Kusumoto T., 753 Kionkowski A. M., 579 Labes M. M., 1 Lachowski E. E., 1379 Lagow R. J., 917 Lai S-W., 469 Maury F., 1501 McKeown N. B., 315 McLendon G., 369 McMurdo J., 149 Meinhold R.H., 821, 833 Menges B., 1319 Mercey B., 165, 1141 Merle-Mejean T., 595 Michel C., 175, 1549 Miller J. S., 1521 Parker M. J., 911 Paronen M., 1309 Partridge R. D., 183 Paschke R., 1283 Peacock R. D., 1259 Pearson C., 699 Pedrini C., 381 Peeters K., 239 Pei Y., 1521 Pelizzi C., 1319 Sanchez-Soto P. J., 1557 Sanchis M. J., 547 Sanders G. M., 357 Sano T., 605 Santos M., 975 Sasaki S., 501 Sat0 M., 1067, 1191 Sauer C., 1087 Sayle D. C., 653 Scheler U., 1219 Teraoka Y., 97 Teunis C. J., 357 Thatcher J. H., 1099 Thiebaut B., 1379 Thompson D. P., 1031 Tirado J. L., Toda K., 1067 Tomkinson J., 449 Tomlinson A. A. G., 645, 37, 41, 861 66 1 Laine R. M., 1441 Lambrecht W. R. L., 899 Minami T., 459 Minceva-Sukarova B., 761 Pelloquin D., 175, 1549 Pelzl G., 1283 Schnelle W., 635 Schoonman J., 765 Topfer J., Torell L., 1511 1309 Lanzetta R., 1473 Laureiro Y., 1517 Lavela P., 41, 861 Misawa M., 1191 Mitchell G.R., 1479 Mitov I. G., 1035 Peng B-X., 559, 1325 Peng Z-H., 559, 1325 Pereira-Ramos J-P., 37 Schouten P. G., 357 Schulz E., 1107 Sdoukos A. T., 887 Toriumi M., 705 Torkkeli M., 1309 Torncrona A., 213 Lebuis A-M., 1075 Lecante P., 1527 Mittler-Neher S., Miura O., 727 1319 Perez-Rodriguez J. L., Perrin M-A., 653 1557 Segal N., 395 Sekine T., 1231 Torres Martinez L. M., 1533 Le Cras F., 1591 Lecuire J-M., 773 Lee C. K., 331 Lee C. Y., 1131 Lee E., 109, 871 Lee G. R., 187 Lee M., 1079 Le Flem G., 381 Lehtinen T., 1309 Miyachi K., 671 Miyasaka H., 705 Miyata F., 711 Miyazaki A., 119 Miyazaki K., 727 Moffat J.B., 459 Mohai I., 1175 Moine B., 381 Monk P. M. S., 183 Pertierra P., 415 Petric A,, 1347 Petrunenko I. A., 207 Petty M. C., 699 Picard C., 619 Piccirillo C., 567 Pickett N. L., 507 Pizarro J. L., 421 Pohmer J., 957 Serimaa R., 1309 Sermon P. A., 1019, 1025 Serrano J. L., 349, 533, Seshadri R., 1585 Sheldon T. J., 1253 Sherrington D. C., 719 Shibata K., 691, 1113 Shinton S., 667 1291 Toyne K. J., 919, 1271 Tran V. H., 429 Traversa E., 1355 Treacher K. E., 315 Treadwell D. R., 1441 Tredgold R. H., 375 Tremayne M., 1601 Tretyakov Y. D., 623 Trindade T., 343 Lemaire M., 1107 Moon J. H., 365 Pola J., 155, 975 Shirai Y., 711 Troc R., 429 Lequan M., 5, 555 Lequan R. M., 5, 555 Le Quesne J. P., 1361 Lerner M.M., 103 Leskela M., 161, 983, 1497 Morales J., 37, 41, 861 Moran E., 1517 Mori T., 501 Moriga T., 459 Morineau R., 505 Pomonis P. J., 887 Poojary D. M., 639 Portemer F., 1543 Porzio W., 1319 Pottgen R., 63, 429, 635, Shirakawa Y., 1191 Shirota Y., 117 Shitara Y., 11 Silvert P-Y., 573 Simonin L., 1595 Trombe J-C., 1527 Truffa E., 1507 Trujillano R., 1419 Tschierske C., 1087, 1283, 1297, 1465 Leskela T., 781 Lezama L. M., 421 Morioka H., Mosel B. D., 1235 635, 801 Powell A. V., 801 807, 1579 Singh N., Sironi A., 629 661 Tsodikov M. V., 207 Tsuchimori M., 1487 1'HCritier P., 1165 Mosset A., 789, 1527 Predieri G., 1319 Skjerlie K. P., 595 Tsuji M., 605 Li S., 1207 Mueller B. L., 1441 Prellier W., 165 Slade R. C. T., 73, 629 Tsutsumi A., 727 Li Y-J., 691 Lin C.L., 1 Mulley S., 661 Mullmann R., 635, 801 Pringle P. G., 993 Pyzuk W., 733 Smart L. E., 221 Smeulders J. B. A. F., 871 Tuffin R. P., 1271 Tundo P., 15 Lin J., 265 Linda11 C. M., 1259 Lindroos S., 161, 983, 1497 Liu C. S., 1131 Muramatsu H., 1113 Muto A., 1241 Nagase Y., 711 Naito H., 33 Qian M., 435 Qun L., 559 Radaev S. F., 1413 Radhakrishnan T. P., 1119 Smith I. K., 539 Smith J. R., 295 Smith M. E., 261, 337 Smith W., 1385 Tunega D., 629 Tunger H-W., 739 Turner S. S., 1521 Uddin M. A,, 1241 Liu S., 305 Livage J., 505 Llavona R., 415 Loiseau T., 1073 Najdoski M. Z., 761 Nakano H., 117 Nakaya T., 691 Nakazumi H., 1113 Ramachandra Rao C. N., 1585 Ranjan R., 131 Rao K. J., 391 Smrcok L., 629 Soraru G. D., 585 Southern J.C., 73 Stefanis A. De., 661 Uddin R., 527 Ueno T., 705 Ulibarri M. A,, 1199 Urbanova M., 975 Lorriaux-Rubbens A., 385 Lose D., 1297 Lougnot D. J., 1595 Loukatzikou L. A., 887 Narayana Rao D., 11 19 Nasman J., 1309 Neat R. J., 49 Needs R. L., 1219 Rasheed R. K., 277 Rasika Abeysinghe J., 155 Ratcliffe N. M., 289, 295, 301 Steuernagel S., 261 Stoev M., 377 Stradling E. P., 1211 Strobe1 P., 1591 Uzunova E. L., 1035 Vaidhyanathan B., 391 Valigi M., 403 Valli L., 15 Loveday D. C., 993 Lowendahl L., 213 Nemoto N., 711 Neumann B., 1087 Rauhala E., 27 Rautanen J., 781 Su Q., 265 Suarez M., 415 van der Put P. J. J. M., van de Velde G. M. H., 765 357 Lunkwitz R., Lynch D. E., Machida M., 1283 23 69, 455 Newport R. J., 337, 449 Nickel K. G., 595 Nieminen M., 27 Raveau B., 165, 175, 1141, 1245, 1549, 1585 Ravi M., 1119 Subbanna G.N., 1429 Subramanian M. A., 867 Subrt J., 155 van Dijk M., 357 Vannier R-N., 1339 Vansant E. F., 239 MacKenzie K. J. D., 821, Macklin W. J., 49 Madarasz J., 781 Madroiiero A., 1059 Magri P., 773 Mai S-M., 1099 Maignan A., 1245, 1549, Mairesse G., 1339 833, 1225 1585 Nii H., 97 Niinisto L., 27, 781 Niori T., 1231 Noma N., 117 Nortier P., 653 Nowogrocki G., 1339 Nutz U., 1283 Nygren M., 97 O'Brien P., 343, 1135 Oestreich S., 807 Rawson J. M., 1161 Rawson J. O., 253 Razafitrimo H., 369 Reynes A., 1501 Rigden J. S., 337, 449 Riley F. L., 1175 Rio C. d., 947 Rives V., 1199, 1419 Rodriguez J., 415 Rodriguez M. L., 415 Sudholter E. J. R., 357, Sugahara Y., 69, 1055 Sugiyama S., 459 Sun Y., 1019, 1025 Sundaresan A., 1549 Sundholm F., 1309 Sundholm G., 1309 Sung K., 917 Suzuki H., 501 1469 Varadaraju U.V., 1549 Vaughan White G., 1225 Vaughey J. T., 81 Vente J. F., 395, 1187 Verdu M., 1059 Viau G., 1047 Vijayakrishnan V., 573 Vill V., 739 Vitek J., 975 Vogt T., 81 11 Volpe P., 1507 von Minden M., 739 Wait S. T., 1161 Waldner K. F., 1441 Watts J. F., 479 Weller M. T., 1219 West A. R., 331, 1379, 1533 Whale E. A., 1479 Wong G. K., 1075 Woolley M., 375 Wright P. V., 947 Wu Y., 1391 Yao T., 33, 1195 Yasukawa A., 1401 Yonehara H., 143 Yonezawa S., 795 Zhao X. S., 1493 Zhong Q., 443 Zhou H., 1075 Z~OUX-F., 559, 1325 Walker T. W., 969 Wallart F., 385 Walton R. I., 611 Whitfield H. J., 261 Widany J., 899 Widernik T., 579 Wybourne M.N., 1249 Xia W. S., 1493 Xu R., 465, 1207 Yoshino H., 501 Yu A. C., 1493 Yue Y., 465, 1207, 1391 Zhuang H., 1391 Zimmer B., 547 Zissi S., 1595 Wang S., 265 Warman J. M., 357 Watanabe J., 1231 Watanabe O., 1487 Watson M. J., 919 Wignacourt J. P., 385 Williams D. E., 409, 1351 Williams G., 539, 667 Willis M. R., 1361 Winfield J. M., 227 Yamamoto N., 1195 Yamamoto T., 705 Yan M., 1249 Yan Q., 1041 Yao J., 143 Zeng H. C., 435 Zhang B., 639 Zhang H., 265, 615 Zhang L., 999 Zhang P., 615 ZouY., Zyss J., 1347 1123 ... 111 Conference Diary 1996 September 1-6 XIth International Symposium on Organosilicon Chemistry Montpellier, France Professor R.J.P. Corriu, Laboratoire des Precurseurs Organometalliques de MatBriaux, UMR CNRS 44, Universite de Montpellier 11, Place E.Bataillon, CC 007, F34095 Montpellier Cedex 5, France. Fax: +67 14 38 88. September 1-6 ECME 96, Third European Conference on Molecular Electronics Leuven, Belgium Professor F.C. De Schryver, Department of Chemistry, K.U. Leuven, Celestijnenlaan 200 F, B-3001 Heverlee, Belgium. September 3-6 7th International Conference on Ferrites Bordeaux, France V. Cagan, Scientific organization, ICF 7 General Secretary Office, Laboratoires du CNRS, 92195 Neudon, France. E-mail: vladimir.cagan@physique.uvsq.fr;Tel: +33 39 25 46 62; Fax: +33 139 25 46 52 September 9-10 Molecular Modelling of Chemicals and Materials Amsterdam, The Netherlands Dr A.M. Brouwer, Laboratory of Organic Chemistry, Amsterdam Institute of Molecular Studies (AIMS), Nieuwe Achtergracht 129, 1018 WS Amsterdam, The Netherlands.E-mail: mgms@chem.uva.nl; Fax: 31 (0120 5255670; WWW page: http://krop.chem.uva.nl/mgms/ 0 September 9-11 Polar Solids Discussion Group -High Temperature Superconductivity 10 Fife, Scotland Dr John T.S. Irvine or Dr P. Lightfoot, School of Chemistry, St Andrews University, St Andrews, Fife KY16 9ST, Scotland. E-mail: jtsi@st-and.ac.uk; Tel: +1334 463817; Fax: +1334 463808 September 10-15 Reactivity in Organised Microstructures: Chemical Reactions and Physical Processes in Compartmentalized Systems Santiago de Compostela, Spain Dr Josip Hendekovic, European Science Foundation, 1quai Lezay-Mamesia, 67080 Strasbourg Cedex, France.E-mail: euresco@esf.org; Tel: +33 88 76 71 35; Fax: +33 88 36 69 87 October 9-14 Physical Metallurgy: Interfacial Engineering in Materials Castelvecchio Pascoli, Italy Dr Josip Hendekovic, European Science Foundation, 1quai Lezay-Marnesia, 67080 Strasbourg Cedex, France. E-mail: euresco@esf.c-strasbourg.fr;Tel: +33 88 76 71 35; Fax: +33 88 36 69 87. October 13-18 ISLC '96 15th International Semiconductor Laser Conference Haifa, Can Carmel, Israel IEEE/LEOS, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA. Tel: +1 908 562 3898; Fax: +1 908 562 8434. October 27- 12th International Congress on Advances in Non-Impact Printing Technologies November 1 San Antonio, TX, USA Conference Manager, IS&T, 7003 Kilworth Lane, Springfield, VA 22151, USA.E-mail: imagesoc@us.net; Tel: +1 703 642 9090; Fax: +1 703 642 9094. November 16-23 IS&T/SID Fourth Color Imaging Conference: Color Science, Systems & Applications Scottsdale, AZ,USA Conference Manager, IS&T, 7003 Kilworth Lane, Springfield, VA 22151, USA. E-mail: imagesoc@us.net; Tel: +1 703 642 9090; Fax: +1 703 642 9094. 0 December 16 British Liquid Crystal Society -One Day Symposium -Challenges Ahead in Surfactant Liquid Crystals Wirral, UK Dr I. Howell or Dr P.B. Warren, Unilever Research Port Sunlight Laboratory, Quarry Road East, Bebington Wirral Merseyside, L63 3JW, UK. E-mail: patrick.warren@unilever.com;Tel: +151 471 3407/3812; Fax: +151 471 812. 1997 April 8 International Symposium on Applications of Magnetic Resonance in Materials Science Guildford, UK Professor G.A.Webb or Dr J.N. Hay, The Department of Chemistry, University of Surrey, Guildford, GU2 5XH, UK. Tel: +1483 300 800; Fax: +1483 259 514 0 April 13-17 Eighth Biennial Workshop on Organometallic Vapor Phase Epitaxy California, USA TMS Customer Service, 420 Commonwealth Drive, Warrendale, PA 15086 USA. E-mail: csc@tms.org; Tel: 412 776 9000 Ext. 270; Fax: 412 776 3770. 0 April 21-25 International Conference on Metallurgical Coatings and Thin Films California, USA Robert V. Hillery, G.E. Aircraft Engines, One Neumann Way, Mail Drop H85,Cincinnati, OH 45215-6301 USA April 22-25 12th International Conference on Solid Compounds of Transition Elements Saint-Malo, France H.Noel, E-mail: scte97@univ-rennesl.fr; Tel: +33 99 28 62 55; Fax: +33 99 63 57 04; http://www.univ-rennesl.fr/scte97. iv May 4-9 Gordon Research Conference on 'Biodegradable Polymers" Barga, Italy Emo Chiellini, Department of Chemistry & Industrial Chemistry, University of Pisa via Risorgimento 35,56126 Pisa, Italy. E-mail: chlmeo@dcci.unipi.it; Tel: +39 50 918299; Fax: +39 50 28438; World Wide Web: http://www.grc.uri.edu. May 25-28 Chemistry, Energy and the Environment 3 Estoril, Portugal Cesar Sequeira, Instituto Superior Tecnico, 1096 Lisboa Cedex, Portugal. Phondax: 351 17783594 May 26-28 EPDIC -5; 5th European Powder Diffraction Conference Parma, Italy Professor G.Artioli, Dipartimento di Scienze della Terra, Universita' di Milano, Via Botticelli 23,I-20133 Milano, Italy.E-mail: artioli@iummix.terra.unimi.it;Tel: +39 2 23698320; Fax: +39 2 70638681 June 3-6 5th International Symposium on Metallomesogens Neuchfitel, Switzerland Professor R. Deschenaux, Universite de Neuchfitel, Institut de Chimie, Av. de Bellevaux 51, 2000 NeuchAtel, Switzerland. E-mail: congres.ism97@ich.unine.ch. July 21-25 The 3rd International Conference on Materials Chemistry University of Exeter, UK. Contact: Dr J.F. Gibson, The Royal Society of Chemistry, Burlington House, London W1V OBN, UK. Fax: +44 (01171 437 8883; WWW: http:llwww.ex.ac.uWchemweb/mc3/ August 17-22 36th IUPAC Congress Geneva, Switzerland Conference Secretariat: IUPAC'97, do AKM Congress Service, PO Box 37, CH-1218 Le Grand-SaconnedGE, Switzerland.Tel: +41 22 761 16 61; Fax: +41 22 761 16 62. August 24-27 ZMPC '97 International Symposium on Zeolites and Microporous Crystals Tokyo, Japan Dr Takahashi Tatsumi, Secretary, ZMPC '97, Engineering Research Institute, Faculty of Engineering, The University of Tokyo, Yayoi, Tokyo 113, Japan. August 31- Third European Congress on Catalysis September 6 Krakbw, Poland Congress Secretariat: EuropaCat-3, Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek, PL-30239 Krakow, Poland. E-mail: ncczenve@cyf-kr.edu.pl; Tel: +48 12 252 814; Fax: +48 12 251 923. September 8-11 ECSSC-97, VIth European Conference on Solid State Chemistry Zurich, Switzerland ECSSC-97, Mrs E Fahrnbuhl, Laboratory of Inorganic Chemistry, ETH Zurich, Universitatstr.6, CH-8092 Zurich, Switzerland. WWW: http:l/www.inorg.chem.ethz.ch/ecssclecssc.hmtl. October 12-17 Composites at Lake Louise '97 Lake Louise, Canada Dr Patrick S. Nicholson, Chairman, Composites at Lake Louise, Department of Materials Science & Engineering, McMaster University, 1280 Main St. West, Hamilton, Ontario, L8S 4L7, Canada. Denotes a new or amended entry this month. Entries in the Conference Diary are published free of charge. If you wish to include an announcement please send full details to: Journal of Materials Chemistry Editorial Office, Thomas Graham House, Science Park, Milton Road, Cambridge, UK, CB4 4WF. Tel: +44 1223 420066; Fax: +44 1223 426017.V *** EUROPEAN RESEARCH CONFERENCES * * * * * * *** PHYSICAL METALLURGY: 5x 0 Interfacial Engineering of Materials xU QJ& I1 Ciocco, near Lucca, (Italy), 9-74 October 79960 Chairman: E.D. Hondros (London, UK) Vice-chairman: H. Grabke (Dusseldorf, Germany) SPEAKERS WILL PROVISIONALLY INCLUDE: 2% S.H. Anastasiadis (Greece) H. Gleiter (Germany) A. Passerone (Italy) % J.L. Baptista (Portugal) H. Grabke (Germany) P. Pieraggi (France) Ew W. Blau (Ireland) S. Hoffman (Germany) R. Ritchie (USA) QJ D. Blavette (France) E.D. Hondros (UK) M. Stoneham (UK) s E. Bullock (Netherlands) C. Humphreys (UK) R. Stroosnijder (Italy) 2 U K.L. Choy (UK) I. Kvernes (Norway) T. Watanabe (Japan) s -.Yh 0 W.Clyne (UK) G. Martin (France) A. Youtsos (Netherlands) K. Friedrich (Germany) M. McLean (UK) L. Zouo (France)3 F. Gesmundo (Italy) R. Mkvrel (France) a,u -SCOPE OF THE CONFERENCE c2 s Q 2 The Meeting will embrace the new understanding of the fine structure of interfaces (grain boundaries, free surfaces, phase interfaces) as well as new information on .the localised y" a, microchemistry. Starting from the treatment of fundamental properties such as the strength of 5s A bonding across interfaces, the Meeting will cover the latest advances in the relation between -0 % grain boundary "type" and strength in polycrystalline metals; the design of two-phase interfaces 2 in composite materials based upon consideration of the localised mechanics and micro- 0 chemistry; the often complex interface between a coating and a metallic matrix and how this may x be tailored to produce the desired adhesion; and the oxide-metal interface and how this may be u engineered to improve the adherence of a protective layer.The conference is open to researchers worldwide, whether from industry or academia. Participation will be limited to 100. The emphasis will be on discussion about new developments. The Registration Fee covers full board and lodging. Grants will be available for younger scientists, in particular those from less favoured regions in Europe. Deadline for applications: 3 months before the conference For information 8, application forms, contact the Executive Director of the Programme: Dr.Josip Hendekovic, European Science Foundation, I quai Lezay-Mamesia, 67080 Strasbourg Cedex, France. Tel.(33) 88 76 71 35 Fax.(33) 88 36 69 87 E-mail: euresco@esf.org on-line information an WWW server at: http:/?hvw. esf. org/euresco MATERIALS CHEMISTRY FORUM The Materials Chemistry Forum of the Royal Society of Chemistry was established in 1993 to promote the emerging discipline of Materials Chemistry, particularly through conferences and cross-subject-group activities. It organises the International Conference Series on Materials Chemistry, MCn as well as a range of more specialised meetings; regional meetings on Materials Chemistry are planned, with the first Scottish meeting scheduled for 1996.The Forum operates in parallel with the Journal of Materials Chemistry so that, together, they give the RSC a broad involvement in developments occurring at the interface between Materials and Chemistry. A key feature of the Forum is the representation on it from seven materials subject groups, not all of which are otherwise affiliated to the RSC. These subject groups are Macrogroup, The British Liquid Crystal Society, The Applied Solid State Chemistry Group, The Polar Solids Group, The Molecular Crystals Discussion Group, the RSC 'Materials Chemistry Sector' and the Society of Chemical Industry's 'Materials Chemistry Group'. For the first time, these various subject groups have a common venue, at the Forum, to discuss and collaborate on topics of common interest. TERMS OF REFERENCE FOR FORUM MEMBERSHIP The Forum membership, with terms of office, is as follows (Nov. 1995): 1. CHAIRMAN: Period of Service: 3 years, renewable 1996 Responsibility of Appointment: SAB 2. CHAIRMAN, JOURNAL OF MATERIALS CHEMISTRY EDITORIAL BOARD ex officio 3. SAB MEMBER: Period of service not set down 4-9 GROUP MEMBERS: Period of Service: 3 years, renewable as follows: MACROGROUP: 1998 BRITISH LIQUID CRYSTAL SOCIETY: 1997 POLAR SOLIDS GROUP: 1996 APPLIED SOLID STATE CHEMISTRY GROUP: 1997 MOLECULAR CRYSTALS GROUP: 1995 MATERIALS CHEMISTRY SECTOR: 1998 10-12. ORGANISERS OF MC" MEETINGS Service commences after MCn-2 and terminates after Forum Committee meeting following MC". 13-14. CO-OPTED MEMBERS optional Current Forum members are: 1. A.R. West 2. A.E. Underhill 3. H.M. Frey 4. S. Armes 5 and 10. D.W. Bruce 6. A.V Chadwick 7. P. O'Brien 8. M. Willis 9. M. Hawkins 11. J.M. Kelly

ISSN:0959-9428    

DOI:10.1039/JM99606BP079

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Nitrodisplacement reactions and the synthesis of bis (ether anhydride) s from dihydroxynapht halenes Geoffrey C. Eastmond" and Jerzy Paprotny Donnan Laboratories, University ofLiverpool, PO Box 147, Liverpool, UK L69 3BX Nitrodisplacement reactions between all ten dihydroxynaphthalenes and 4-nitrophthalodinitrile have been studied. Apart from 1,8-dihydroxynaphthalene,all dihydroxynaphthalenes undergo nitrodisplacement but only 1,5-,2,3-, 2,6-and 2,7- dihydroxynaphthalenes give high yields of pure bis(ether dinitrile). The bis(ether dinitri1e)s produced in high yield were hydrolysed and converted to bis(ether anhydride) for subsequent synthesis of poly(ether imide)s. Success in nitrodisplacement correlates with high redox potentials for the dihydroxynaphthalenes, except for 1,8-dihydroxynaphthalenewhich probably fails to react because of steric constraints at the peri positions.In recent years there has been an emphasis on the development of thermally stable polymers with high thermal-transition temperatures. Such developments have led to a series of commercial polymers such as polyesters, polyamides (e.g. KevlarB, NomexB) and polyimides (e.g. Kaptonm) which are difficult or impossible to process; the structural features which lead to chemical and thermal stability almost automati- cally make processability (in solution or in the melt) difficult. Many of these polymers have a large content of para-linked aromatic residues. The associated geometry assists close-pack- ing of aromatic units and increases inter-chain interactions between amide or phthalimide residues, for example.Two major approaches have been adopted to enhance processability within a given class of polymers. Within the family of polyimides, the development of nucleophilic displace- ment reactions with nitrophthalic acid derivatives led to the synthesis of bis(ether anhydride)s and of more processable poly(ether imide)s with flexible, main-chain, ether linkages; a commercial product is U1temm.l Within the fields of polyesters and polyamides an alternative procedure has been to incorpor- ate naphthalene residues in order to disrupt the essential linearity associated with para-linked units.2 The density of inter-chain interactions may also be reduced. Possible conse- quences of these structural modifications are that thermal- transition temperatures may be reduced and solubilities enhanced.While the development of bis(ether anhydride)s and, hence, poly(ether imide)s has been a very active research area, there has been very little activity directed to the incorporation of naphthalene residues. Existing reports on the incorporation of naphthalene residues into polyimides fall into two categories. One is the incorporation of naphthalene residues into diamines; this objective has been achieved by either the use of naphtha- lene diamines3 or bis(ether diamine)s based on naphthalene residues4 or of bis(ether diamine)s in polya~partimides.~ The second is the use of 1,4,5,8-naphthalenetetracarboxylicacid dianhydride6 or 4,4-(phenylene-1,3-dicarbonyl)dinaphthalene-1,8,1',8'-tetracarboxylic acid dianhydride7 or other related monomers.8 This latter approach incorporates large, flat, rigid, dianhydride units which will not increase chain flexibility. What is missing from this scenario is the incorporation of naphthalene units into bis(ether anhydride) units and, hence, into conventional poly(ether imide)s.That is, there is a lack of evidence for nitrodisplacement reactions between naphtha- lenes and phthalic acid derivatives. In the course of a recent study of nitrodisplacement reactions with aromatic diols, we demonstrated that while the sodium salt of 1,5-dihydroxynaphthalenewill not undergo nitrodis- placement with N-phenyl-4-nitrophthalimide according to Scheme 1, a common route to bis(ether phthalic acid) deriva- tives, 1,5-dihydroxynaphthalene will undergo nitrodisplace- ment with 4-nitrophthalonitrile according to Scheme 2.Also, we recently reported a successful nitrodisplacement reaction between 2,3-dihydroxynaphthaleneand 4-nitro~hthalonitrile.~ The bis(ether dinitrile) prepared from 2,3-dihydroxynaphtha- lene was also converted into a bis(ether anhydride) and a soluble polymer was prepared from it and 4,4'-diamino-phenyl ether. OH OH OH I I OH IIa tIb IIC OH OH bH IId HOJQ6 IIe IIf m: HOgjQJm IIh IIi HowoH Ten dihydroxynaphthalenes I1 are available. In order to assess the general feasibility of incorporating naphthalene residues into poly(ether imide)s we undertook a survey of nitrodisplacement reactions between all ten dihydroxynaphtha- lenes and 4-nitrophthalonitrile I.This paper reports the results of that investigation and the synthesis of the corresponding bis(ether dinitri1e)s and the bis(ether anhydride)s prepared from the tetranitriles according to Scheme 2. This paper there- fore extends our general study aimed at identifying which aromatic dihydroxy compounds will, and which will not, J. Mater. Chem., 1996,6(9), 1455-1458 1455 + DMSONa ___) 0-Ar-0&a 0 0 Scheme 1 I IKOH,MOOH Q HOZCHo2c~O-Nap-0 V N Scheme 2 undergo nitrodisplacement. This distinction ultimately estab- lishes which naphthalene residues can be incorporated into the anhydride units of poly(ether imide)s.A companion paper" describes the synthesis of poly (ether imide)s from each of the bis(ether anhydride)s synthesized successfully here in order to illustrate the feasibility of synthes- izing high-molecular-weight poly (ether imide) s with naphtha- lene residues in anhydride moieties. That paper also reports on the properties of the poly(ether imide)s synthesized. Experimenta1 All dihydroxynaphthalenes II, except for the 1,2- and 1,8- isomers, were obtained commercially. The 1,3-, 1,4-, 1,5-, 1,6- and 2,6-isomers were obtained from Aldrich and were recrys- tallized prior to use. 2,3- and 2,7-dihydroxynaphthaleneswere obtained from Fluka, 1,7-dihydroxynaphthalenewas from TCI. 1,2-Dihydroxynaphthalenewas synthesized from 1,2-naph- thoquinone (Aldrich) by reduction with sodium hydrogensulfite according to the procedure of Fieser and Fieser;" mp 101-103 "C (lit., 108 "C) (Calc for CloH,O,: C, 74.99; H, 5.03.Found; C, 74.77; H, 4.95 YO).1,8-Dihydroxynaphthalenewas synthesized from 1,8-naphthosultone (Aldrich) according to the procedure of Erdmann;12 mp 142-144°C (lit., 144°C) (Calc. for CloHsOz: C, 74.98; H, 5.03. Found: C, 74.89; H, 4.98 Yo). 4-Nitrophthalodinitrile (TCI), anhydrous dimethyl sulfoxide (DMSO) (Aldrich) and other general purpose reagents were used as received. 4,4'-Oxydianiline (ODA) was an ultra-pure sample from BP. Bis-aniline A was synthesized as described previously. Nitrodisplacement reactions were performed in 100 cm3 flasks with a magnetic stirrer bar.Into 50 cm3 anhydrous DMSO, 21 mmol of 4-nitrophthalodinitrile I was dissolved, followed by 10 mmol of the requisite dihydroxynaphthalene; the solutions became dark or very dark yellow. Then 5 g of anhydrous potassium carbonate was added. The mixture was stirred under nitrogen at room temperature for 24 h then poured into 400 cm3 of water and the coloured precipitate was filtered off and washed a few times with water until the washings were neutral. The crude bis(ether dinitrile) I11 was washed with methanol and recrystallized from acetonitrile. The above procedure yielded high purity bis(ether dinitri1e)s from 1,5-, 2,3-, 2,6- and 2,7-dihydroxynaphthalenes,and the products were highly crystalline and white or off-white in colour.In the cases of 1,2-, 1,3-, 1,4-, 1,6-and 1,7-dihydroxyna- phthalenes, multiple recrystallizations were required ( 10 recrys- tallizations in the case of the 1,4-isomer) to achieve products with sharp melting points and which were white or pale in colour. Elemental analysis results, yields and melting point data for the bis(ether dinitri1e)s are given in Table 1. Further confirmation of product structures was obtained by IR and NMR spectroscopy and mass spectrometry. Individual bis(ether dinitri1e)s were hydrolysed by the same procedure. Bis(ether dinitrile) (5 g) was dispersed in 10 cm3 of a 50wt% aqueous solution of potassium hydroxide. Then 10-20 cm3 methanol was added, sufficient to wet the bis(ether dinitrile) and produce a smooth suspension.The suspension was boiled under reflux until the evolution of ammonia could not be detected; typical reaction times were 30-40 h. The solution was then diluted to 300cm3 with water, filtered and acidified to pH 1.5-2 with concentrated HC1 while stirred. The Table 1 Nitrodisplacements with dihydroxynaphthalenes product elemental yield diol E,/mV analysis (Oh) (%) C 75.72 calculated H 2.91 mp/"C 207-208 160- 162 238-239 264.8-265.6 175- 176.5 166- 167 IIa IIb IIC IId IIe IIf IIg IIh IIi IIj N 13.59 C 75.56 555, 576 H 2.90 18.44 N 13.61 C 75.60 7 54 H 2.88 15 N 13.51 C 75.29 484 H 2.88 13.4 N 13.69 c 74.44 731 H 2.89 91.0 N 13.17 C 75.63 -H 2.92 53.4 N 13.55 c 75.95 -H 2.86 51.1 N 13.70 no bis(ether 758 dinitrile) c 75.59 880 H 2.89 99.22 265-266 N 13.51 C 75.66 785 H 2.90 98.3 267-268 N 13.63 C 74.84 1075 H 3.08 97.0 203.5-204.3 N 14.56 1456 J.Muter. Chem., 1996, 6(9), 1455-1458 Table 2 Bis(ether anhydride)s derived from naphthalene bis(ether dinitri1e)s bis(ether elemental accurate anhydride) analysis (YO) mass/Da mp/"C calculated C 69.05 452.05322 H 2.65 Vd C 68.30 452.05334 255-256 H 2.65 Vh C 68.95 452.05290 264.6-265.4 H 2.57 Vi C 68.70 452.05334 237-238 H 2.61 Vj C 68.93 452.05290 165-167 H 2.63 acid was filtered off and the product was washed with water until neutral when it was filtered and dried.Yields in all cases were 98-99% theoretical. The resulting bis(ether acid)s IV were not characterized but were used directly in the synthesis of bis(ether anhydride)s V. The same general procedure was adopted for the synthesis of all bis(ether anhydride)s. Bis(ether acid) (10 g) was sus-pended or partially dissolved in 150 cm3 of glacial acetic acid and brought to 80-90 "C, when 200 cm3 of acetic anhydride was added and the mixture refluxed for 30min. On cooling, the bis(ether anhydride) started to crystallize and the product was filtered off next day. The product was recrystallized from a small volume of acetic anhydride. In all cases yields were about 90-95% theoretical; elemental analysis data are pre- sented in Table 2.Results and Discussion The results of the several nitrodisplacement reactions, per- formed according to Scheme 2, are presented in Table 1. These data show that four dihydroxynaphthalenes (IId, h-j) will undergo nitrodisplacement with 4-nitrophthalonitrile I satisfac-torily to yield the desired bis(ether dinitrile) in almost quanti- tative yield (Table 1); yields quoted are those of pure recrystallized products rather than crude yields. It is immediately obvious from the data in Table 1 that while all dihydroxynaphthalenes which do not carry a hydroxy group in the 1-position (IIh-j) will undergo nitrodisplacement to give pure products in almost quantitative yield, of the dihydroxynaphthalenes which do have a 1-hydroxy group only the 1,5-isomer IId will satisfactorily undergo nitrodisplacement to give a virtually quantitative yield of the pure bis(ether dinitrile).All nitrodisplacement reaction mixtures were initially highly coloured and in successful reactions, i.e. those which gave a high yield of bis(ether dinitrile), the colour gradually faded. However, all dihydroxynaphthalenes having a 1-hydroxy group, other than the reaction mixture with 1,5-dihydroxyna- phthalene (i.e. IIa-c, e-g), produced dark, almost black, reac- tion mixtures when the 4-nitrophthalodinitrile I was added; some initial, crude products from these reactions were almost tar-like. Nevertheless, in most cases it was possible to extract some bis(ether dinitrile) from the reaction products with sufficient purity to obtain correct elemental analyses and sharp melting points.Such products were usually the minor product and in no case was the yield of bis(ether dinitrile) as high as 60% theoretical. The identity of the bis(ether dinitrile) was confirmed by a combination of tools, in addition to elemental analysis. For example, that the product obtained in low yield from the nitrodisplacement reaction with 1,4-dihydroxynaph- thalene was the bis(ether dinitrile) was confirmed by identify- ing the IR CN stretching frequencies of bis(ether dinitri1e)s from several dihydroxynaphthalenes ( 1,4-, 2231.9 cm-'; 1,5-, 2231.6 cm-l; 2,3-, 2230.3 cm-l; 2,6-, 2232.3 cm-l; 2,7-, 2232.0 cm-'). In addition, the accurate masses of the molecular ions, determined by mass spectrometry, from the products of the displacement reactions were 412.09632 Da with 1,4-dihydroxynaphthalene, compared with 412.09591 Da for the isomeric product from 2,3-dihydroxynaphthaleneand a calcu- lated value of 412.09604 Da.It is also clear from the data in Table 1 that of all dihydroxy- naphthalenes, only 1,8-dihydroxynaphthalenefailed to undergo nitrodisplacement and yield any of the desired product. We have previously noted that failure to undergo nitrodisplace- ment reactions and the formation of impure products in low yields is often associated with low redox potentials (E,/V) of the diols. The same trend is observed here in that difficulty in achieving successful reactions and pure products is generally related to the redox potential of the dihydroxynaphthalene.The redox potential of 1,8-dihydroxynaphthaleneis relatively high (758 mV) and the reason that 1,8-dihydroxynaphthalene fails to undergo nitrodisplacement is almost certainly due to steric constraints associated with the close proximity of the hydroxy groups in the peri positions. In most cases where the nitrodisplacement reaction was unsuccessful in producing the desired bis(ether dinitrile) in high yield no attempt was made to identify the alternative reaction products; usually no product was readily obtained in crystalline form. For 1,4-dihydroxynaphthalene,however, the major reaction product was readily isolated as a brick-red, crystalline material with a molecular weight, identified by mass spectrometry, of 299 g mol- l, and a melting point of ca.300 "C; its composition, determined by elemental analysis was: C, 70.52; H, 2.89; N, 13.84%, compared with that for the bis(ether dinitrile) and the calculated values in Table 1. Overall, the data obtained indicate that, apart from 1,8-di hydrox ynap ht halene, all di hydroxy nap h thalenes will undergo nitrodisplacement to produce bis(ether dinitrile) to at least some extent and, in principle, it should be possible to hydrolyse all nine bis(ether dinitri1e)s to the corresponding bis(ether diacid)s and, hence, convert them to the correspond- ing bis(ether anhydride)s. It should be possible, therefore, to incorporate the nine naphthalene residues (apart from 1,8- residues) into the anhydride units of poly(ether imide)s.However, it is clear from the experimental results that consider- able difficulty was experienced in producing even low yields of pure bis(ether dinitrile) from most dihydroxynaphthalenes having 1-hydroxy residues. Previous experience has shown that, ultimately, the production of high-purity bis(ether dini- trile) is crucial in the successful synthesis of high-molecular- weight poly(ether imide)s. In cases where it was difficult to produce low yields of bis(ether dinitri1e)s of sufficient purity to obtain good analyses and sharp melting points, the products were usually insufficiently pure to yield bis(ether anhydride)s of the necessary purity to obtain high-molecular-weight poly(- ether imide)s.While it might be possible, in principle, to synthesize poly(ether imide)s based on nine of the naphthalene units, this could only sensibly be done on a small scale. Consequently, it is only practical to consider converting bis(ether dinitri1e)s IIId, h-j into bis(ether anhydride)s and incorporating those naphthalene residues into poly(ether imide)s. The bis(ether dinitri1e)s identified in Table 1 as being pro- duced in high yield (i.e. IIId, h-j) were all readily hydrolysed according to Scheme2, and as described above, into the corresponding bis(ether diacid)s IV and subsequently dehy- drated with acetic anhydride into the bis(ether anhydride)s V. Elemental analyses and accurate masses, determined by mass spectrometry, for the isomeric anhydrides are all essentially identical and are given in Table 2.The bis(ether anhydride)s listed in Table 2 were all reacted, in solution, with aromatic diamines, by a conventional two- stage synthesis with chemical imidization, to produce poly(- ether imide)s. The results of those syntheses and a description J. Muter. Chem., 1996, 6(9), 1455-1458 1457 of the characterization and properties of the polymers is described in a companion paper lo Conclusions Of the ten available dihydroxynaphthalenes all, except for 1,8- dihydroxynaphthalene, undergo nitrodisplacement with 4-nitrophthalodinitrile to yield bis(ether dinitri1e)s However, for dihydroxynaphthalenes with hydroxy groups in the 1-position except for 175-dihydroxynaphthalene,yields of pure products were very low The bis(ether dinitri1e)s from 1,5-,2,3-, 2,6- and 2,7-dihydroxynaphthaleneswere hydrolysed and converted to bis(ether anhydnde)s capable of being used in the synthesis of high-molecular-weight poly (ether imide)s The authors wish to thank the SERC and the DRA for the financial support which allowed this work to be undertaken References 1 R 0 Johnson and H S Burhlis, J Polym Scz Polym Symp, 1983, 70,129 2 J Preston, Angew Makromol Chem, 1982,109/110,1 3 H H Gibbs, J Appl Polym Scz Appl Polym Symp, 1979,35,207, H H Gibbs and C V Breder, Adu Chem Ser, 1975,142,442 4 C-P Yang and W-T Chen, Macromolecules, 1993, 26, 4865, J Polym Scz Part A Polym Chem Ed, 1994,32,435 5 C-S Wang and H-J Hwang, Polymer, 1996,37,499 6 H Ghassemi and A S Hay, Macromolecules, 1994,27,3116 7 D Sek, P Pijet and A Wanic, Polymer, 1992, 33, 190, D Sek, A Wanic and E Schab-Balcerzak, Polymer, 1993,34,2440 8 A L Rusanov and E G Bulycheva, in Polyzmzdes and other Hzgh- temperature Polymers, ed M J M Abadie and B Sillion Elsevier, Amsterdam, 1991,p 125 9 G C Eastmond and J Paprotny, Macromolecules, 1995,28,2140 10 G C Eastmond and J Paprotny, J Muter Chem ,following paper 11 L Fieser and M Fieser, J Am Chem SOC,1934,56,1565 12 H Erdmann, Annalen, 1888,247,345 Paper 6/02620F, Received 15th April 1996 1458 J Muter Chem, 1996, 6(9), 1455-1458

ISSN:0959-9428    

DOI:10.1039/JM9960601455

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Synthesis and properties of poly (ether imide) s derived from dihydroxynaphthalenes Geoffrey C. Eastmond" and Jerzy Paprotny Donnan Laboratories, University of Liverpool, PO Box 147, Liverpool L69 3BX, UK Poly(ether imide)s were synthesized from bis(ether anhydride)s derived from 1,5-, 2,3-, 2,6- and 2,7-dihydroxynaphthalenesand various aromatic diamines using a two-stage solution process, normally with chemical imidization. During the synthesis of polymers from the bis(ether anhydride) from 2,3-dihydroxynaphthaleneand 4,4'-oxydianiline (4,4'-ODA), by both chemical and thermal imidization, small proportions of a relatively insoluble, infusible, crystalline solid were produced. It is proposed that this product is a cyclic oligomer. Solubilities of the polymers were assessed and, where sufficiently soluble, molecular weights were determined by gel permeation chromatography.Apart from polymers based on 2,3-naphthalene units, the polymers had limited solubilities. Glass-transition temperatures were determined; all were in excess of 220 "C, some were in excess of 300 "C. Several poly(ether imide)s based on ODA, were found to be thermally stable to 590 "C. Polymers based on the bis(ether anhydride) derived from 2,3-dihydroxynaphthalenegave strong solvent-cast films with high moduli extensions to break were modest except for the polymer from the diamine BAPB which extended to 150% prior to fracture. Naphthalene units have been incorporated into polymers over the years in order to achieve a variety of effects.Early workers used naphthalene units to increase glass-transition tempera- tures of polymers. Subsequently naphthalene units were intro- duced to decrease glass-transition and processing temperatures of polyarylates, especially of liquid crystalline polyesters. Often, naphthalene units are used to replace a proportion of other aromatic residues in order to produce copolymers which are more processable than the parent polymer. Korshak et al.' produced polyesters with high melting points based on 1,2-dihydroxynaphthalene.Jedlinski and Sek' synthe- sized polyesters with bisnaphthylene and binaphthyl residues by reacting their diols with terephthaloyl chloride. The bisnaphthylene units incorporated flexible links (e.g. -CH,-) as well as the rigid naphthylene moieties, while the binaphthyl residues incorporated units with a large dihedral angle which might disrupt chain packing.These various polymers had melting points in the range 340-420°C and a polymer with bisnaphthylene units had a melting point of 340 "C, compared with 270 "C for the corresponding polymer with bis-p-phenyl- ene units. In liquid crystalline polymers, liquid crystallinity can be maintained while incorporating 1,4-, 1,5- or 2,6-substituted naphthalene units in which the bonds incorporating those units into the chain are co-linear or ~arallel.~ Other structures introduce non-linearity into chains and disrupt liquid crystal- linity. The units may be incorporated into the copolymers as diols or as dicarboxylic acids.Introducing these units in place of 1,4-phenylene units provides a rigid structure which disrupts chain packing and reduces thermal transition temperatures in the resulting copolyesters. A copolyester based on 4-hydroxy- benzoic acid and 2,6-dihydroxynaphthoic acid is commer-cialized as Ve~tra.~ The 2,6-naphthalene unit is very effective in reducing melting points of copolymers while 1,4- or 1,5-units give melting points too high for pro~essing.~ Poly(ethy1ene naphthalene-2,6-dicarboxylate)(PEN) has been introduced, as an alternative to poly(ethy1ene terephthal- ate); 2,6-naphthalene units give enhanced physical and mechan- ical proper tie^.^ PEN crystallizes and has low solubility. A polymer equivalent to PEN was one of a series of polyesters based on naphthalene units which were among the first poly- esters to be synthesized.6 Amorphous copolyesters with higher solubilities have been prepared.' In contrast, there are few instances of polyimides incorporat- ing naphthalene residues and little information on or under- standing of the nature and properties of the resulting polymers or copolymers.To date, studies by other workers fall into two main categories: (i) structures containing the imide derived from 1,8-naphthalenedicarboxylicacid units; (ii) polymers in which the amine residue contains a naphthalene moiety. Within category (i), polymers based on 1,4,5,8-naphthalene- tetracarboxylic acid dianhydride have been prepared. This structure, which was converted to its diaminobisimide and used as a diamine monomer, incorporates a large disc-like unit into the polymer backbone, cf.pyromellitic dianhydride; poly(- ether imide)s so formed were found to be soluble and to have high glass-transition temperatures.' Another study used dian- hydrides containing two 1,8-naphthalenedicarboxylicacid dianhydride units with an intermediate link so that two rigid moieties are incorporated per unit." A further study employed 4,4'- binaph thyl- 1,1',8,8'-tetracarbox ylic acid dianh ydride, which also incorporates two rigid moieties per unit, with a large intermediate dihedral angle. In the latter case, polymers were prepared with a variety of aliphatic and aromatic diamines and, except for polymers based on p-phenylene diamine, were mainly found to be soluble in chlorinated as well as aprotic solvents; glass-transition temperatures for aromatic polymers were in excess of 400°C and the polymers were thermally stable." In category (ii), 1,5-diaminonaphthalene was polymerized with 6FDA [2,2-bis( 3,4-dicarboxyphenyl) hexafluoropropane dianhydride] and was found to increase the glass-transition temperature relative to p-phenylene diamine and to give poly- mers with good modulus but reduced extension to break.12 Such polymers of modest molecular weight were found to be soluble in a number of solvents, e.g.tetrahydrofuran and dich10romethane.l~ We recently reported the synthesis of a series of new poly(- ether imide)s based on catechol and its derivatives.This series includes a poly(ether imide) based on the bis(ether anhydride) 2,3-NBA, derived from 2,3-dihydroxynaphthalene.14There is also a report of a diamine derived from the same dihydroxyna- phthalene being used in polyimide synthesis." Following our investigation of nitrodisplacement reactions between 4-nitroph- thalodinitrile and dihydroxynaphthalenes and the identifi- cation of which dihydroxynaphthalenes can be readily converted into bis(ether anhydride),16 we now report on a preliminary study of the synthesis and properties of poly(ether imide)s based on bis(ether anhydride)s derived from 1,5-,2,3-, 2,6- and 2,7-dihydroxynaphthalenes.These bis(ether anhy- dride)s are identified J. Muter. Chem., 1996, 6(9), 1459-1464 1459 1.5-NBA 2,3-NBA 0 0OyJq-p3$ Q 2,6-NBA 0 0 0mqo 0 0 by a code in accordance with that used previo~sly;'~ the numerical component corresponds to the substitution pattern of the naphthalene moiety and polymers are identified as 2,3- NBA/MPD (polymer from 2,3-NBA and MPD) etc.With other dihydroxynaphthalenes nitrodisplacement reactions are so inefficient that the reactions are unrealistic as potential sources of commercial materials, although their study might be fruitful subsequently to provide a more complete knowledge of structure-property relationships. Experimental Bis(ether anhydride)s derived from 1,5-, 2,3-, 2,6- and 2,7- dihydroxynaphthalenes were prepared as described in the preceding paper.16 Diamines were obtained from sources ident- ified previously. l5 Other reagents and solvents were general laboratory reagents.Polymer synthesis Polymer syntheses were carried out by two conventional two- stage syntheses (Scheme 1). In both cases anhydride and 0 0 &O, Py or heatI diamine were reacted in solution to form poly(amic acid). In one case the poly(amic acid) was imidized chemically and in the other thermally. Typical syntheses are described below. Chemical imidization. In a reaction flask fitted with a magnetic stirrer, 4 mmol of diamine was dissolved in 25 cm3 1-methyl-2-pyrrolidinone (NMP), and an exact stoichiometric equivalence of bis(ether anhydride) was added in one portion with stirring at room temperature. After reacting for one day, when the mixture had become very viscous due to the forma- tion of poly(amic acid), the polymer was imidized by addition of an excess of a 50: 50 v/v mixture of acetic anhydride and pyridine.The mixture was allowed to react for at least 6 h and usually overnight. The poly(ether imide) was isolated by drop- wise addition of the solution into a large excess of methanol, at which point the polymer usually precipitated as small yellow balls. The polymer was filtered off and added to a further large volume of methanol and the mixture boiled for several hours to remove residual solvent and imidizing reagents. This process was repeated, after which the polymer was filtered off and dried under vacuum at 110 "C. Yields were approximately quantitative.Thermal imidization. About 8 mmol of diamine was added to a flask fitted with a magnetic stirrer and a nitrogen bleed and was dissolved in 40 cm3 of NMP. An exact equivalence of bis(ether anhydride) was added and the mixture reacted as above to form poly(amic acid). A small sample of poly(amic acid) was removed and imidized chemically. Then 20cm3 xylene was added and the reaction flask was fitted with a Dean-Stark trap. The mixture was brought to the boil at 160 "C and water was removed as its xylene azeotrope in order to effect imidization. If the solution remained homogeneous refluxing was continued for 30 h after which the mixture was cooled and the polymer extracted as described for chemical imidization.When 4,4'-ODA was used as diamine the polymer started to precipitate out in the early stages of imidization and some xylene was removed to improve the solvent quality. This procedure raised the boiling point to about 190°C but some insoluble powder always remained. The insoluble material was separated by filtration. Refluxing was continued to complete thermal imidization, no further precipitate formed and the polymer was isolated from homogeneous solution as described above. Polymer characterization Molecular weights were determined by gel-permeation chroma- tography using DMF with 1 mol dm-3 lithium chloride as the mobile phase, as described previ0us1y.l~ Glass-transition tem- peratures were determined with the aid of a Perkin-Elmer DSC-2.Solubilities of the polymers were determined in a series of solvents by allowing samples of polymer to stand in solvents for a period of two weeks. Samples of some polymers were cast as films from 5-7 wt.% filtered (0.45 pm) homogeneous solutions in chloroform by slow drying at room temperature in flat-bottomed petri dishes and subsequently heating under vacuum at 140 "C. Dumbbell-shaped samples were cut from the films and mechanical properties were determined using an Instron tensile tester. Results and Discussion Poly(ether imide)s were prepared from the four bis(ether Scheme 1 anhydride)s identified (see following page) 1460 J. Muter. Chem., 1996, 6(9), 1459-1464 H2NTYH2 MPD 4,4'-ODA H2N, & ! - D H 2 3,4'-ODA BAA BAP TPE-Q TPE-R BAPB TMB XMBD BAA-GF CF, MPD-CFS and a series of diamines.Polymers investigated were mainly prepared in NMP solution with chemical imidization (Scheme 1). Polymerizationof 2,3-NBA with 4,4'-ODA Some unusual observations were made during the synthesis and handling of 2,3-NBA/4,4'-ODA poly(ether imide)s. Preparation according to the standard procedure produced a homogeneous solution on chemical imidization and the poly- mer was isolated by dropwise precipitation into methanol. During subsequent solvent-casting, from homogeneous solu- tions, of films for mechanical testing, it was found that the polymer gave a cloudy film and, subsequently, was not totally soluble in chloroform but gave a cloudy solution.A white solid was separated by filtration through a 0.45 pm filter; the solid was retained. A film was cast from the clear solution but was hazy when dry; other poly(ether imide)s prepared gave optically clear films except 2,3-NBA/BAPB which also devel- oped some haziness when cast. Samples of 2,3-NBA/4,4'-ODA were also prepared by ther- mal imidization of the poly(amic acid) solution, as described above. During the first hour of heating at 160"C, while refluxing in the presence of xylene, a white precipitate formed. The composition of the solvent mixture was modified by addition of NMP, to improve solvent quality, and the reflux temperature was raised to 190°C; the solid did not dissolve. This powder, which constituted 8 wt% of the total solids, was isolated and retained.Further prolonged heating did not produce any further precipitate. Both white solids had virtually identical compositions, as determined by elemental analysis, and similar to that of polymer prepared from the same constituents. The calculated composition for the poly(ether imide) is C, 74.02; H, 3.52; N, 4.55%. The composition of the solid isolated from the chemi- cally imidized polymer was C, 70.85; H, 3.55; N, 4.60% and that from the thermally imidized sample was C, 70.28; H, 3.26; N, 4.43%; it is normal for carbon contents of aromatic polymers as determined by elemental analysis to be slightly lower than calculated. The solids, which were totally insoluble in chloroform or NMP (both are solvents for the polymer) and even in methanesulfonic acid, were only soluble in concen- trated sulfuric acid.The solids did not exhibit a glass-transition (there was possibly an extremely weak transition at 240 "C) and the solid did not fuse or decompose on heating in air to temperatures up to 550 "C on a hotplate. No useful information was obtained from mass spectrometry of samples in concen- trated sulfuric acid. The solids and polymer had almost ident- ical infrared spectra and contained absorptions at all the characteristic frequencies for polyimides identified by Dine- Hart and Wright." In the fingerprint region all peak frequen- cies, for both the solid and the polymer, were identical to within 2cm-' and all peak intensities were identical except for very small differences at and between 1112.8 and 1076.2 cm-', between 880.7 and 831.5 cm-' and at 672 cm-'.The polymer exhibited small absorptions at about 3500 cm-' which were absent in the white powder and could have arisen from amino groups. It was also demonstrated by X-ray powder diffraction that, while polymer films were amorphous, the white powder was highly crystalline. At present we are unable to make a positive identification of the nature of the solid powders. They do not have the characteristics of relatively insoluble high molecular weight polymer; they showed no signs of swelling, even in hot NMP, in solvents for the polymer, even after standing in those solvents for ten months. It also seems incomprehensible that 8 wt% of a polymer with a peak molecular weight by gel permeation chromatography (approximately the weight-aver- age molecular weight) of 40 kg mol-' could be so insoluble and crystalline when the same polymer, prepared by chemical imidization with a peak molecular weight of 90 kg mol-' was almost totally soluble in chloroform and amorphous.Gel permeation chromatograms of most poly(ether imide) s pre-pared show distinct peaks at low molecular weights corre- sponding to dimer and trimer species and we suggest that the solids isolated might in fact be insoluble cyclic oligomers. This proposal is consistent with small amino absorptions in the infrared spectrum of the polymer. Further, cyclic polycarbonate oligomers are highly crystalline and the polyimide equivalents could be very insoluble.Proof of this proposal requires further study and if we are able to establish the identity if the powder we will report the results separately. J. Mater. Chem., 1996,6(9), 1459-1464 1461 Characterization Table 2 Solubilities of poly(ether imide)s formed from naphthalene bis(ether anhydride)s" Molecular weights. Molecular weights of several polymers soluble in DMF-LiCl( 1M), possibly after dissolution in NMP anhydride and dilution into DMF-LiCl, were determined by gel per- 1,5-NBA 2,3-NBA 2,6-NBA 2,7-NBAmeation chromatography, and the results are presented in amine Table 1 Molecular weights quoted correspond to peaks of the MPD CHCI, p CHCl, s NMP (hot) s NMP (hot)chromatograms, based on polystyrene standards In a few DMA i DMA trg trgcases with 2,7-NBA, poly(amic acid)s were prepared in two NMP s cresol s different solvents [NMP and dimethylacetamide (DMA)] 4,4-ODA cresol trg CHC1, p cresol s DMA trg according to the standard procedure described above It was H,SO,s DMAs NMP s NMP s observed that molecular weights of poly(ether imide)s formed 3,4-ODA CHC1, p CHCl, sin DMA were greater than those of polymers prepared in CHCI, s CHCI, s DMA iNMP, solubilities of the polymers prepared in NMP were NMP s lower, consistent with higher molecular weight BAA CHC1, s -CHCI, s CHCI, s Polymer solubilities were tested in a series of solvents BAP CHCl, s -hot cresol s CHCI, p Normally for such polymers the solvent power is in the order DMA trg NMP s conc H,S04 >cresol >NMP >DMA >DMF >CHC1, TPE-Q -CHCl, s, trg -NMP trg cresol sIn some solvents polymers were only partially soluble (high- TPER -CHC1, s -cresol s molecular-weight fractions were probably insoluble) and poly- BAPB -CHCl, s cresol trg cresol trg -CHCI, smers were only soluble in hot solvents and formed thermally MBXD CHC1, s CHCI, s -CHC1, sreversible gels on cooling, in a few cases polymers swelled in TMB cresol s CHCl, s hot solvents to form gels The results of several tests are MPD CF, CHCl, s CHCl, s NMP s summarised in Table2 For several polymers not all cases of BAA-6F CHCl, s CHCl, s -NMP s CHCl, s CHC1, sinsolubility are recorded Unless otherwise stated, if a polymer is designated to be soluble in one solvent it can be assumed "Key s, soluble, 1, insoluble, p, partially soluble, trg, forms a thermally that it is soluble in the more powerful solvents in the above reversible gel on cooling from hot solution list, otherwise polymers were not soluble in solvents not identified The influences of the different naphthalene units may be compared with different phenylene units Thus, 1,5- and 2,6-naphthalene units may be compared with the hydro- quinone unit but with linkages parallel and offset rather than Table 3 Glass-transition temperaturesrc of poly(ether 1mide)s formed co-linear Similarly, the 2,7-naphthalene unit might be likened from naphthalene bis(ether anhydride)s to a resorcinol unit and 2,3-naphthalene to catechol, 2,3- anhydridedihydroxynaphthalene is a benzannelated catechol The same pattern of solubilities is found for naphthalene as for phenylene amine 1,5-NBA 2,3-NBA 2,6-NBA 2,7-NBA units Thus, 2,3-naphthalene units impart much greater solu- bility than the other units, as do catechol and substituted MPD 260 255 Tg 230 2 54 catechols when compared with hydroquinone or resorcinol 4,4-ODA T, 340 240 235 249 245and their derivatives l9 3,4-ODA 235 226 225 221 BAA 265 -236 247 Tbermal-transition temperatures.Glass-transition tempera- BAP 253 -246 246 tures of the poly(ether imide)s were determined and the results TPE-Q -229 -228 are summarised in Table 3 To a first approximation, the glass- TPE-R -208 -not found -227 230 23 1 transition temperatures of the polymers are independent of the BAPB 28 1 265 -272substitution pattern of the naphthalene units Otherwise, glass- MBXD TMB not found 308 -not found transition temperatures fit with previously established patterns MPD-CF, 250 250 -235 in that glass-transition temperatures increase with the rigidity BAA-6F 276 256 218 256 of the diamine unit and with reduced possibilities of rotation about linkages to the imide units Thus, MPD-based polymers Table 1 Molecular weights (kg mol I) of poly(ether imide)s formed from naphthalene bis(ether anhydride)s anhydride method of amine imidization 1,5-NBA 2,3-NBA 2,6-NBA 2,7-NBA ~~____ a 4 aMPD chemical 70 4.4-ODA chemical a 94 a 46 thermal -41 a3,4-ODA chemical 60 41 39 BAA chemical 54 23 37 BAP chemical 78 -a 146 aTPE-Q chemical 170 4TPE-R chemical 68 aBAPB chemical -127 MBXD chemical 62 97 92 TMB chemical a 56 34 -7MPD-CF, chemical 25 34 BAA-6F chemical 89 52 56 47 "Insoluble in DMF-LiCl (1 mol dm ,) 1462 J Muter Chem, 1996, 6(9), 1459-1464 have slightly higher Tg values than those based on the more flexible 4,4'-ODA unit (10-20 "C) and the latter polymers have slightly higher $ values (5-25 "C) than those based on the unsymmetrical 3,4'-ODA.The lowest G is for a polymer based on TPE-R, which incorporates two flexible ether linkages into a single chain unit and also introduces additional non-linearity. In contrast, higher Tg values are observed for polymers based on MBXD, in which ortho-methyl groups are adjacent to the linkages to phthalimide units, which restricts chain rotation although it does not restrict any hinge in the system.20 The highest Tg values observed are for polymers based on TMB which not only has ortho-methyl groups which restrict group rotations but also incorporates a rigid biphenyl moiety.High G values are also observed for polymers having fluorinated units. In one case (MPD-CF,) there is a pendant trifluorome- thy1 group which increases the bulkiness of groups which might be required to undergo rotation and in the other (BAA- 6F) this group increases the stiffness of a hinge unit in the chain, cf. BAA. To date only one polymer, 2,6-NBA/MPD, has been shown to be crystallizable, with a melting point of 340°C. Thermogravimetric analysis.Polymers prepared from each of the naphthalene bis(ether anhydride)s and 4,4'-ODA, and additionally the polymer 1,5-NBA/BAA, were subjected to thermogravimetric analysis in air; heating rates were 10 "C min-l. All polymers showed good thermal stability, and thermograms of the polymers based on 4,4'-ODA are given in Fig. 1. Polymers 2,3-NBA/4,4'-ODA and 2,7-NBA/4,4'-ODA exhibited the greatest thermal stabilities; their thermograms were practically superimposable. These polymers did not start to decompose below 560°C and they lost 96% of their weight between that temperature and 740 "C; 4% weight loss was gradual on heating from ambient temperature and was prob- ably due to loss of residual solvent.2,6-NBA/4,4'-ODA lost 96% between 547 and 690 "C; there is little distinction between onsets of degradation for 2,3-NBA/4,4'-ODA, 2,6-NBA/4,4'- ODA and 2,7-NBA/4,4-ODA, but 2,6-NBA/4,4'-ODA lost weight more rapidly. The least stable polymer of the series was 1,5-NBA/4,4'-ODA, which showed 98% weight loss between 390 and 667°C. The polymer 1,5-NBA/BAA showed a 95% weight loss between 473 and 713 "C, of which about 10% was lost at about 580°C. It is interesting to compare the thermal stabilities of these polymers with the related poly(ether imide)s, in which the central units of the bis(ether anhydride)s are differently substi- tuted phenylenes; i.e. Nap in I is replaced by phenylene. Takekoshi et uL21 have previously reported the thermal stabilit- ies of poly(ether imide)s derived from 4,4'-ODA and the bis (ether anhydride) s derived from hydroquinone and resorci- I I I L 190 350 510 670 830 TPC Fig. 1 Thermogravimetric data for: (a) 2,3-NBA/4,4-ODA and 2,7-NBA/4,4'-ODA (thermograms are superimposed); (b) 2,6-NBA/4,4-ODA; (c) 1,5-NBA/4,4'-ODA nol, HBA and RBA, respectively, and we have reported on the thermal stability of that based on 4,4'-ODA and catechol bis(ether anhydride) CBA.17,22 Takekoshi et al.reported that, in air, HBA/4,4'-ODA and RBA/4,4'-ODA suffered 5 % weight loss at 553 and 537 "C, respectively; under nitrogen, decompo- sition temperatures were about 20 "C higher. For CBA/4,4- ODA we reported initial weight loss at 450°C and maximum rate of weight loss at 560°C.Thus, 2,3-NBA/4,4'-ODA and 2,7-NBA/4,4-ODA show greater thermal stabilities than CBA/4,4'-0DA, the parent polymer of 2,3-NBA/4,4'-ODA, and have thermal stabilities at least comparable with the corre- sponding poly(ether imide)s based on HBA and RBA. Mechanical properties Because many of the polymers based on naphthalene bis(ether anhydride)s are insoluble in solvents suitable for solvent casting of films, studies of mechanical properties concentrated on polymers based on 2,3-NBA, which is of course a catechol derivative, and these results may be compared with our pre- vious results for poly(ether imide)s based on catechol bis(ether anhydride) (CBA).22 The mechanical properties of several poly (ether imide) s based on 2,3-NBA and several different diamines were deter- mined.The results are summarized in Table4. Samples were cut from solvent-cast films with a dumbbell-shaped cutter. Many poly(ether imide)s are tough and yield before fracture. In this study a number of polymers showed brittle fracture at low elongations (cu. 5% extension) and these results conform with those we reported recently for poly(ether imide)s based on catechol bis(ether anhydride)s.22 However, a few samples yielded at low extensions and exhibited strain-hardening prior to fracture. For some polymers both types of behaviour were observed in different samples. It is difficult in these circum- stances to define true behaviour but we assume that, where observed, yielding is more representative of true behaviour and that failure to yield was a result of premature fracture, possibly because of small defects introduced on sample prep- aration; maximal values of parameters are recorded in Table 4, average values are given in brackets.The molecular weights of the polymers prepared in this study are not optimal and it is probable that better properties are achievable. The initial moduli of all polymers prepared are high and for several are comparable to those of Kapton2, and Ultem (2.96 GPa).Z4 Ultimate strengths are less than that of Kapton (172 MPa) but higher than that of Ultem (105 MPa). In most cases, however, elongations to break are less than those of the commercial materials (60-70%). This range of properties, in terms of modulus and strength, are superior to those of polymers based on the parent catechol bis(ether anhydride) (CBA), reported previously.22 An exception to the low exten- sions to break are the data for 2,3-NBA/BAPB, which showed a maximal extension to break of 135%.This result is quite exceptional compared with the properties of the other polymers synthesized in this study. It is, however, comparable to the data for the corresponding polymer CBA/BAPB, which exhib- ited 170% extension to break.22 We speculated previously on the origins of this behaviour but its actual origin remains obscure. Overall, the results for 2,3-NBA/BAPB confirm our previous conclusions and show that poly(ether imide)s based on catechol and its derivatives are capable of providing materials which are highly processable and have excellent properties.Conclusions Bis(ether anhydride)s based on the 1,5-, 2,3-, 2,6- and 2,7- substituted naphthalene units can be used to incorporate naphthalene residues into poly(ether imide)s by polymerization with any of several aromatic diamines. Synthesis was achieved J. Muter. Chem., 1996, 6(9), 1459-1464 1463 Table 4 Mechanical properties of some poly(ether imide)s based on 2,3-NBAa method of initial modulus/ yield stress/ elongation ultimate stress/ elongation amine imidization GPa MPa (%) MPa (Yo) MPD chemical 2 91 95 1 ODA thermal (2 7) 2 48 (88)104 4,4-ODA chemical (2 24) 2 88 109 6 89 90 3 3,4-ODA chemical (2 65) 2 65 - - 99 8 BAP chemical (2 47) 27 - - 118 2(86 7) BAPB chemical (2 6) 26 117 4 93 120 4 (111) TMB chemical (2 42) 34 120 6 (113 2) 88(9) (107 3) 140 (2 8) (119 7) (8 7) (124) 'Maximal parameters Average values given in brackets by a conventional two-stage solution polymenzation involving intermediate formation of the poly(amic acid) followed by chemical imidization Glass-transition temperatures of the polymers exceed 220 "C and, for some diamines, exceed 300°C or are unobservable below 450 "C The transition temperatures are largely indepen- dent of the substitution pattern of the naphthalene residue in the anhydnde moiety but vary with the structure of the diamine Variations in glass-transition temperature follow pre- viously established patterns in that rigid diamines, especially those with substituents which hinder rotation, raise glass- transition temperatures, while flexible residues lower glass- transition temperatures Of all the polymers investigated, only that based on the anhydnde 2,6-NBA and MPD was found to be crystallizable It was established that the polymers have good thermal stabilities in air Polymers based on 4,4'-ODA and three of the anhydndes are stable to about 550°C, the polymer based on 1,5-NBA has a lower stability, decomposition starts at 390 "C Polymer solubilities vary with the structure of the diamine used Many of the polymers have limited solubilities and several give thermally-reversible gels in solvents such as NMP, DMA and cresol However, polymers based on 2,3-NBA, a catechol derivative, are far more soluble than those based on other naphthalene bis(ether anhydr1de)s This observation parallels the previously found high solubility of poly(ether imide)s based on catechol in comparison with the analogues based on hydroquinone and resorcinol Many polymers based on 2,3-NBA had sufficiently high molecular weights and solubilities to be cast into films Most of these polymers exhibited high moduli and strengths but relatively low extensions to break, failure to yield may have been due to limited molecular weights in some cases The polymer based on 2,3-NBA and BAPB yields and shows a large (135%) extension to break, a similar result was observed previously with the analogous polymer based on the parent catechol bis(ether anhydride) and BAPB The authors wish to thank Dr N C Billingham for thermo- gravimetric analysis data, Valerie Laberthe, an ERASMUS student, for measurements of mechanical properties and Dr M Harding for help with X-ray diffraction The authors also thank the SERC and the DRA for financial support References 1 V V Korshak, S V Vinogradova and M A Iskenderov, Vysokomol Soedzn ,1962,4,345 2 Z Jedlinski and D Sek, J Polym Sci A-1,1969,7,2587 3 W J Jackson, Jr ,Macromolecules, 1983,16,1027 4 G W Calunden, USP 4,161,470, 1979 5 Saturated Polyester Resin Handbook, ed K Yuki, Nikan Industnal Publisher, Japan, 1990, p 874 6 G J Cooke, H P W Huggdl and A R Lowe, unpublished results quoted in ref 7 7 R Hill and E E Walker, J Polym Sci ,1948,3, 609 8 C -S Wang and Y -M Sun, Polym Prepr Am Chem SOC Dzv Polym Chem ,1996,36,197 9 H Ghassemi and A S Hay, Macromolecules, 1994,27, 3 116 10 D Sek, P Pijet and A Wanik, Polymer, 1992,33, 190 11 J P Gao and Z Y Wang, J Polym Sci Part A Polym Chem, 1995,33,1627 12 H H Gibbs and C V Breder, in Copolymer Polyblends and Composites, ed N A J Platzer, Adv Chem Ser 142, ACS, Washington, 1975 13 G R Husk, P E Cassidy and K L Gebert, Macromolecules, 1988, 21,1234 14 G C Eastmond and J Paprotny, Macromolecules, 1995,28,2140 15 C-P Yang and W-T Chen, Macromolecules 1993, 26, 4865, J Polym Scz Part A, 1994,32,5148 16 G C Eastmond and J Paprotny, J Muter Chem, preceding paper17 G C Eastmond and J Paprotny, Polymer, 1994,35,5148 18 R A Dine-Hart and W W Wnght, Makromol Chem, 1971, 143, 189 19 G C Eastmond and J Paprotny, Reactive and Functional Polymers, 1996,30,21 20 G C Eastmond, J Paprotny and I Webster, Polymer, 1993, 34, 2865 21 T Takekoshi, J E Kochanowski, J S Manello and M J Webber, J Polym Sci Polym Symp ,1986,74,93 22 G C Eastmond and J Paprotny, Macromolecules, 1996,29,1382 23 Du Pont Technical Information Bulletin H2, 1966 24 R 0 Johnson and H S Burhlis, J Polym Sci Polym Symp, 1983, 70,129 Paper 6/02622B, Received 15th April 1996 1464 J Muter Chem, 1996, 6(9), 1459-1464

ISSN:0959-9428    

DOI:10.1039/JM9960601459

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Ferrocene-containing thermotropic liquid crystals: laterally connected twins Jens Andersch,” Siegmar Dieleb and Carsten Tschierske”“ “Martin-Luther-UniversitatHalle, Institut fur Organische Chemie, 0-06120 Halle, Kurt-Mothes-Str. 2 Germany bMartin-Luther-UniversitatHalle, Institut fur Physikalische Chemie, 0-06108 Halle, Muhlpforte 1, Germany A novel type of liquid crystalline ferrocene derivatives has been synthesised and investigated. These metallomesogens consist of two rod-like 4,4”-disubstituted p-terphenyl rigid cores which are laterally connected to each other via spacers incorporating 1,l’-disubstituted ferrocene units. These materials have broad smectic A mesophases and considerably increased mesomorphic ranges in comparison to the structurally related derivatives incorporating a 1,4-disubstituted benzene ring instead of the ferrocene unit in the spacer.For comparison, a molecule consisting of a single 4,4”-disubstituted p-terphenyl unit carrying a lateral ferrocene substituent and the corresponding benzoate were also prepared and investigated. Since the discovery of ferrocene in 1951, this molecule and its derivatives have found many uses, for example as homogeneous catalysts, in enantioselective synthesis and as redoxactive mate- rials.’ Also, a large number of liquid crystalline derivatives have been de~cribed.~.~ Most of these compounds are calamitic molecules incorporating a 1,l’- or 1,3-disubstituted ferrocene- diyl unit as a part of the calamitic core. Also, polymeric derivatives4 and mesomorphic ferro~enophanes~ have been described.However, the ferrocene unit is a poor component of mesogens. It is only tolerated if the molecule is long enough to compensate for the reduction of mesogenic properties induced by its inclusion. Therefore, the replacement of a 1,4- disubstituted benzene ring in the rigid core of a calamitic liquid crystal by a 1,l’-disubstituted ferrocene unit usually leads to a dramatic reduction of the clearing points.6 K 107 (N 63)I K 138 Sc 176 N 280 I Also, the 1,3-disubstituted derivatives7 need long promeso- genic units attached to the ferrocene unit in order to exhibit mesophases. This can be attributed to the fact that the ferrocene moiety is bulky and that it gives rise to a more or less bent molecular structure.Furthermore, due to the internal rotation of the cyclopentadienyl rings’ the 1,l’-disubstituted ferrocenes are not as rigid as the related benzene derivatives. The first These compounds represent the first ferrocene derivatives in which the ferrocene is connected in a lateral position to rigid organic rods. 0 Phl K 132(SA94) I Fe2 K 144 SA140 IPh2 1,1’,3-trisubstituted ferrocenes have recently been rep~rted.~ These compounds display an increased mesophase stability if compared with analogous 1,3-disubstituted and 1,l’-disubsti- tuted ferrocene derivatives. The authors propose that the bulkiness of the ferrocene unit is hidden by the third substituent Fe3at the ferrocene. Results and Discussion We wish to report a novel type of ferrocene containing liquid crystals which have comparable or even higher clearing tem- Ph3 peratures compared to structurally related benzene derivatives.J. Mater. Chem., 1996, 6(9), 1465-1468 1465 Compounds Fel and Fe2 consist of two 4,4"-disubstituted p-terphenyl units, which are laterally connected by ferrocene containing bridging groups They were obtained by esterifi- cation of 1,l'-ferrocenedicarboxylicacid with 4,4"-didecyloxy- 2'-( hydr~xymethyl)-p-terphenyl'~ and 4,4-didecyloxy-3-(hydroxymethyl)-p-terphenylllusing a water soluble carbodi- imide as condensation agent" as detailed in the Experimental section below Compound Fe3, which carries a lateral ferrocene unit, was synthesised accordingly from ferrocenecarboxylic acid and 4,4"-didecyloxy-3-( hydroxymethy1)-p-terphenyl The terephthalates Phl13 and Ph2 as well as the benzoate Ph3, which contain terephthaloyl groups or a benzoyl group instead of the ferrocene units, were synthesised as reference compounds to evaluate the influence of the ferrocene species on the mesomorphic properties (see Experimental section) The meso- morphic properties were investigated by polarised optical microscopy, by differential scanning calorimetry and X-ray diffraction studies The transition temperatures and the transi- tion enthalpies of all compounds are summarised in Table 1 Mesogenic twins The 2',2'-connected ferrocene derivative Fel shows an enanti- otropic smectic A-phase in the temperature range 86-102 "C This mesophase was easily identified, as a typical texture was observed (focal conic fan texture with homeotropic regions) The 3,3-connected ferrocene derivative Fe2 also displays a smectic A-phase, however with a considerably higher clearing temperature This is in accordance with our recent results, which have shown that shifting the lateral bridging unit from the centre to a more peripheral position increases the meso- phase stability of laterally connected mesogenic twins As is obvious from Fig 1, the liquid crystalline state of compound Fe2 can be supercooled down to room temperature without crystallisation Even after storage for several months, only partial crystallisation was observed Also, compounds Fel and Phl can be supercooled without crystallisation, but crystallis- ation sets in after several hours On the other hand compound Ph2 immediately crystallises at 97 "C Because the viscosities of all twins are in the same order of magnitude, the different crystallisation tendency should not be caused by it X-Ray scattering proved the smectic layer structures and gave the layer periodicities (Fel: d=3 35, Fe2: d=3 55 and Ph2 d =3 55 nm, determined in the middle of the temperature ranges of the S,-phases) The thickness of the smectic layers of all compounds is smaller than the length of their single calamitic units (L=4 1 nm) This is in agreement with our Table 1 Transition temperatures/"C and associated enthalpy values/kJ mol (lower lines in brackets) of the compounds Fel-3 and Phl-3" comp K sc SA N 1 Tcryst Fel 86 102 0 -0-b 0-0 (65 7) (14 3) -(0 94)" 0 -0-Phl 0 132 b (82 9) (15 0) -0-Fe2 120 0 -0 153 b (7)d (25 4) 149 -0 97Ph2 122'/144 -(74 0"/28 8) (14 7) 89 96 -0 59Fe3 0-0 (11 8) (8 4) 0 0 0Ph3 0 75 0 77 91 93 61 (41 7) (0 3) (2 4If "Data were taken from the first heating scan (lOK min-l), K, crystalline solid, Sc, smectic C-phase, SA,smectic A-phase, N, nematic phase, I, isotropic liquid, Tcryst, Temperature of crystallisation, taken from the first DSC-cooling scan (10 K min-l) No crystallisation on cooling down to -20 "C Monotropic mesophase No complete crystallisation 'Transition between two solid modifications Not resolved 1466 J Mater Chem, 1996, 6(9), 1465-1468 iil 35 55 0= 50 I I I I I I 25 50 75 100 125 150 TI% Fig.1 DSC heating and cooling traces of compound Fe2 (10 K min-l, first heating is recorded after storage of the molten sample for two months at 20 "C, the second heating scan was taken immediately after cooling) model in which the terphenyl units are arranged parallel to the layer normal in the S,-phase The difference between the layer thickness and the estimated molecular length can be explained by a large number of gauche conformers in the chains The bulky central parts lead to a free volume which is compensated by the fluid chains Most surprising, however, is the fact that the ferrocene derivatives Fel and Fe2 have comparable or even higher clearing temperatures than the structurally related terephthal- ates Phl and Ph2 This could not be expected, since the ferrocene-1,l'-diyl unit represents a much more bulky group compared to the terephthaloyl unit Furthermore, the melting temperatures of the ferrocene derivatives are significantly lower In this way a significantly larger mesomorphic region results for the ferrocenes The reason for this finding is not clear yet, but one can assume that the flexibility of the ferrocene unit allows an improved arrangement of the individual molecules in the layers and probably minimises the disturbance caused by the rigid structure of the terephthalates Laterally substituted p-terphenyls In order to evaluate the influence of steric factors,14 the laterally substituted p-terphenyl derivatives Fe3 and Ph3 were also synthesised Surprisingly, again the more bulky ferrocene derivative Fe3 displays a more stable smectic A phase than the benzoate Ph3 Additionally, the nematic phase of compound Ph3 is missing in the analogous ferrocene Fe3 This means that the bulky ferrocene unit gives rise to an increased structural order An enantiotropic S,-phase is additionally observed on cooling the benzoate Ph3 below 77 "C (detected by formation of a Schlieren texture in the homeotropically aligned regions of the S,-phase) The S,-phase is not found by cooling the analogous ferrocene derivative Fe3 down to 61 "C Rapid crystallisation occurs at this temperature Obviously the S,-phase is destabilised by the bulky ferrocene unit Contrary to the S,-phase the SA-meso- phase is not destabilised by increasing the size of the lateral substituent This can only be explained if additional attractive forces exist which can counterbalance the disturbance caused by the steric repulsion15 These attractive forces may result from a better polarisability of the ferrocene group It seems that there is an inherent mesophase stabilising influence of the ferrocene unit However, in most known cases this mesophase stabilising effect is hidden behind the unfavourable steric and conformational properties In summary, first ferrocene derivatives with the ferrocene unit laterally connected to rigid rods have been synthesised These metallomesogens have broad mesomorphic ranges It is especially interesting that the S,-phase of the ferrocene deriva- tives are not destabilised, but even slightly stabilised in com- parison to the related benzoates.Thus, these compounds may be interesting candidates for elaborating liquid crystalline materials for electroactive molecular units. This work was carried out with support from the BASF-AG, the BMBF, and the Fonds der Chemischen Industrie. Experimental General Confirmation of the structures of intermediates and products was obtained by ‘H NMR spectroscopy (Varian Unity 500); proton chemical shifts are quoted relative to an internal deuterium lock. Mass spectra were recorded on an AMD 402 mass spectrometer (70 eV) or by MS Engine 5989 A with Electrospray 59987 A.The purity of all compounds was checked by thin layer chromatography (TLC; aluminium sheets, silica gel 60 F254 from Merck). Microanalyses were performed using an Leco CHNS-932 elemental analyser. Mesomorphic properties were studied by heated stage polar- ising microscopy using a Nikon Optiphot-2 polarising micro- scope equipped with a Mettler FP 82 HT hot stage and control unit and were confirmed using differential scanning calorimetry (Perkin Elmer DSC-7). X-Ray studies were performed by means of a Guinier-goniometer (Fa. Huber). Bis[( 4,4”-didecyloxyterphenyl-2’-yl)methyl]ferrocene-1,l’-dicarboxylate Fel 1,l‘-Ferrocenedicarboxylic acid (0.27 g, 1.0 mmol), N-cyclo- hexyl-h”-(2-morpholinoethyl )carbodiimide methyl-toluene-p-sulfonatet( 0.84 g, 2.0 mmol) and 4-dimethylaminopyridine (DMAP) (0.06 g, 0.5 mmol) were dissolved in dry dichloro- methane (10 ml) and cooled to 0 “C.4,4-Didecyloxy-2’- (hydroxymethy1)-p-terphenyl(l.4g, 2.4 mmol) dissolved in dry dichloromethane (10 ml) was added via a syringe. The solution was allowed to warm up to room temperature and stirred for 10 h. The solvent was removed in uucuo and the residue was dissolved in diethyl ether (20 ml) and neutralized with 3 M hydrochloric acid. The organic phase was separated and dried with Na,SO,. After evaporation of the solvent the crude product was purified by column chromatography (silica gel, chloroform) and crystallised from acetone. Yield: 0.21 g (15%) (Found: C, 78.04; H, 8.55; Cg0H,,,Fe08 requires C, 78.12; H, 8.60%); 8, (CDCl,): 0.87 (t, 12 H, CH,), 1.22-1.37 (m, 48 H, CH,), 1.40-1.46 (m, 8 H, OCH,CH,CH2), 1.73-1.79 (m, 8 H, OCH,CH,), 3.93 (t, 4 H, PhOCH,), 3.95 (t, 4 H, PhOCH,), 4.23 (m, 4 H, 3,4-H-Cp, 3’,4-H-Cp), 4.77 (m, 4 H, 2,5-H-Cp, 2’,5’-H-Cp), 5.18 (s, 4 H, PhCH,-0), 6.92 (dt, 8 H, 3,5-H-Ar, 3”,5”-H-Ar), 7.30 (dt, 4 H, 2”,6”-H-Ar), 7.33 (d, 2 H, 6’-H-Ar), 7.52 (dt, 4 H, 2,6-H-Ar), 7.53 (dd, 2 H, 5’-H-Ar), 7.72 (d, 2 H, 3’-H-Ar); Electrospray MS : 1422.3 [M +K] +, 1406.2 [M+Na]+, 1383.2 [M+H]+.Bis [( 4,4”-didecyloxyterphenyl-3-y1)methyl] ferrocene-1,l’- dicarboxylate Fe2 Synthesized as described for Fel from 1,l’-ferro-cenedicarboxylic acid (0.27 g, 1.0 mmol), and 4,4”-didecyloxy- 3-(hydroxymethy1)-p-terphenyl (1.4 g, 2.4 mmol).Yield: 0.60 g (43%) (Found: C, 77.77; H, 8.45; C,,H,,,FeO, requires: C, 78.12; H, 8.60%); G,(CDCl,): 0.86 (t, 6 H, CH,), 0.88 (t, 6 H, CH3), 1.22-1.38 (m, 48 H, CH,), 1.41-1.49 (m, 8 H, OCH,CH,CH,), 1.76-1.82 (m, 8 H, OCH,CH,), 3.97 (t, 4 H, PhOCH,), 4.01 (t, 4 H, PhOCH,), 4.28 (m, 4 H, 3,4-H-Cp, 3’,4-H-Cp), 4.83 (m, 4 H, 2,5-H-Cp, 2’,5’-H-Cp), 5.34 (s, 4 H, -f TUPAC name: N [2-(cyclohexyliminoethylideneamino)ethyl]-N-methylmorpholin-4-ium toluene-p-sulfonate. PhCH,O), 6.92 (d, 2 H, 5-H-Ar), 6.94 (dt, 4 H, 3”,5”-H-Ar), 7.50 (dt, 4 H, 2”,6”-H-Ar), 7.51 (dd, 2 H, 6-H-Ar), 7.54-7.59 (m, 8 H, H‘-Ar), 7.66 (d, 2 H, 2-H-Ar); m/z 1383 (M’, 5%). (4,4-Didecyloxyterphenyl-3-yl )methyl ferrocenecarboxylate Fe3 Synthesized as described for Fel from ferrocenecarboxylic acid (0.14 g, 1 .O mmol) and 4,4”-didecyloxy-3-( hydroxymethy1)-p- terphenyl (0.69 g, 1.2 mmol).Yield: 0.20 g (26%); (Found: C, 76.55; H, 8.18; CSoH6,FeO4 requires: C, 76.51; H, 8.22%); G,(CDCl,): 0.87 (t, 6 H, CH,), 1.22-1.40 (m, 24 H, CH,), 1.43-1.51 (m, 4 H, OCH,CH2-CH,), 1.76-1.87 (m, 4 H, OCH,CH,), 3.99 (t, 2 H, PhOCH,), 4.06 (t, 2 H, PhOCH2),4.11 (s, 5 H, H’-Cp), 4.36 (m, 2 H, 3,4-H-Cp), 4.83 (m, 2 H, 2,5-H- Cp), 5.37 (s, 2 H, PhCH,O), 6.95 (dt, 2 H, 3”,5”-H-Ar), 6.97 (d t, 1 H, 5-H-Ar), 7.53 (d t, 2H, 2”,6”-H-Ar), 7.54 (dd, 1 H, 6-H-Ar), 7.58-7.62 (m, 4 H, H’-Ar), 7.71 (d, 1 H, 2-H-Ar); m/z 784 (M’, 100%). 1,4-Bis[(4,4”-didecyloxyterphenyl-3-yl)methyl] benzene-1,4- dicarboxylate Ph2 Terephthaloyl chloride (0.10 g, 0.5 mmol) was dissolved in dry toluene ( 10 ml).4,4”-Didecyloxy-3-( hydroxymethy1)-p-ter- phenyl(0.69 g, 1.2 mmol), dissolved in a mixture of dry toluene (20 ml) and dry pyridine (0.3 ml) was slowly added via a syringe. Afterwards the reaction mixture was stirred for 4 h at reflux temperature. After cooling to room temperature the solution was extracted twice with HCl (10 ml, loo/) and the solvent was removed in vucuo. The white residue was crystal- lised from hexane-ethyl acetate (5: 1). Yield: 0.57 g (89%); (Found: C, 80.90; H, 9.01; C86H11408 requires: C, 80.96; H, 9.01%); GH (CDCl,): 0.80-0.92 (t, 12 H, CH,), 1.21-1.52 (m, 56 H, CH,), 1.72-1.81 (m, 8 H, OCH,CH,), 3.97 (t, 4 H, PhOCH,), 3.97 (t, 4 H, PhOCH,), 4.02 (t, 4 H, PhOCH,), 5.47 (s, 4 H, PhCH,O), 6.92-7.66 (m, 22 H, H-Ar), 8.12 (s, 4 H, H-Ar); m/z 1275 (M’, 12), 720 (68), 676 (58), 570 (70), 556 (100).(4,4-Didecyloxyterphenyl-3-y1) methyl benzoate Ph3 Synthesized as described for Ph2 from benzoyl chloride (0.12 g, 1.O mmol) and 4,4”-didecyloxy-3-( hydroxymethy1)-p-terphenyl (0.69 g, 1.2 mmol). Crystallised from hexane. Yield: 0.66 g (97%); (Found: C, 81.44; H, 8.82; C4sH&4 requires: C, 81.61; H, 8.93%); 6, (CDCl,): 0.87 (t, 3 H, CH,), 0.88 (t, 3 H, CH,), 1.21-1.38 (m, 24 H, CH,), 1.41-1.49 (m, 4 H, OCH,CH,CH,), 1.76-1.82 (m, 4 H, OCH,CH,), 3.99 (t, 2 H, PhOCH,), 4.04 (t, 4 H, PhOCH,), 5.47 (s, 2 H, PhCH,O), 6.96-7.68 (m, 15 H, H-Ar), 8.08 (dt, 2 H, H-Ar); m/z 676 (M+, loo), 556 (5), 414 (14). References 1 Ferrocenes: Homogeneous Catalysis -Organic Synthesis, Material Science, ed.A. Togni and T. Hayashi, VCH, Weinheim, 1995. 2 Metallomesogens: Synthesis, Properties, and Applications, ed. J. L. Serrano, VCH, Weinheim, 1996. 3 R. Deschenaux and J. W. Goodby, in ref. 1, pp. 470-495. 4 R. Deschenaux, I. Kosztics, U. Scholten, D. Guillon and M. Ibn-Elhaj, J. Muter. Chem., 1994,4,1351. 5 A. Werner and W. Friedrichsen, J. Chem. SOC., Chem. Commun., 1994,365. 6 N. J. Thompson, J. W. Goodby and K. J. Toyne, Liq. Cryst., 1993, 13, 381. 7 R. Deschenaux and J. L. Marendaz, J. Chem. SOC., Chem. Commun., 1991,909. 8 C. Elschenbroich and A. Salzer, in Organometallics, VCH, Weinheim, 1992. 9 R. Deschenaux, I. Kosztics and B. Nicolet, J. Muter. Chem., 1995, 5, 2291. 10 J. Andersch, S. Diele, P. Goring, J. A. Schroter and C. Tschierske, J. Chem. SOC., Chem. Commun., 1995,107. J. Muter. Chem., 1996, 6(9), 1465-1468 1467 11 12 J. Andersch, C. Tschierske, S. Diele and D. Lose, J. Muter. Chem., 1996,6, 1297. C. Tschierske and H. Zaschke, J. Prakt. Chem. 1989,331,365. 15 F. Hildebrandt, J. A. Schroter, C. Tschierske, R. Festag, R. Kleppinger and J. H. Wendorff, Angew. Chem., Int. Ed. engl., 1995,34,1631. 13 14 J. Andersch, S. Diele, D. Lose and C. Tschierske, Liq. Cryst., 1996, 21, 103. W. Weissflog and D. Demus, Crystal Res. & Technol., 1984,19,55. Paper 6/02408D; Received 9th April, 1996 1468 J. Muter. Chem., 1996, 6(9), 1465-1468

ISSN:0959-9428    

DOI:10.1039/JM9960601465

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Thermal and optical properties of chiral twin liquid crystalline bis (cholesteryl ) alkanedioates Antonius T. M. Marcelis, Arie Koudijs and Ernst J. R. Sudholter" Department of Organic Chemistry, Wageningen Agricultural University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands The thermal and optical properties of a series of bis(cholestery1) alkanedioates were investigated. The melting points, the cholesteric to isotropic transition temperatures, the entropy changes at this temperature and the selective reflection wavelengths of the cholesteric phase all exhibit an odd-even effect as a function of spacer length. This is attributed to a difference in the ordering of the cholesteric phase as a function of the parity of the spacer. Because the properties of the members of the series with a short spacer could not be measured for several reasons, their properties were also determined as a 5 wt% solution in a cholesteric host.A similar odd-even influence on the cholesteric to isotropic transition temperatures and the optical properties of the host was observed as for the pure compounds. The influence on the properties of the host is stronger for compounds with a short spacer than for compounds with a longer spacer. An important property of chiral liquid crystals is that the planar oriented cholesteric phase selectively reflects The selective reflection wavelength strongly depends on the chiral centres present in the molecule, but also on the ordering of the molecules in the phase. Twin liquid crystals, for example, consisting of two mesogenic units connected by a flexible spacer, exhibit a strong alternating ordering of the nematic phase as a function of the parity of the Better ordered nematic phases are obtained for twin liquid crystals in which the mesogens are preferentially oriented parallel. This is usually the case when the number of flexible units separating the mesogens is even.Chiral twin liquid crystals can be obtained by introducing chirality in the spaceP9 or in the mesogens.lo-l2 Our recent studies on chiral twin liquid crystals containing steroid properties of a series of these esters will be presented. The study of the properties of these compounds with shorter spacers is complicated, because they are either monotropic and crys- tallize or they decompose due to the high temperatures needed to obtain the cholesteric phase.Therefore, the properties of these compounds were also investigated as a solution in a cholesteric host. Experimental Bis(cholestery1) alkanedioates (I-n) A mixture of 10mmol of the appropriate dicarboxylic acid chloride and 20mmol of cholesterol in 50ml of toluene was refluxed for 3 h. After cooling the solvent was evaporated and the residue was recrystallized from chloroform-ethanol. Yields cu . 80%. 1-3: 'H NMR (CDC13) 6 5.4 (m, 2 H, CH=), 4.65 (m, 2H, CHO), 2.35 (m, 4H, CH2C=0), 2.0-0.7 (m, 51H, aliphatic) (Calc. for C59H9604:C, 81.51; H, 11.13. Found: C, 81.82; H, 11.41%). n=odd Measurements.h mesogens have shown that the selective reflection wavelength of the cholesteric phase also exhibits an odd-even effect as a function of the parity of the connecting spacer.Compounds that give better ordered cholesteric phases give higher selective reflection wavelengths. Furthermore, a different temperature dependence was found for the selective reflection wavelength of compounds with odd and even spacers.13-15 The prototype of chiral twin liquid crystals with steroids as mesogens are the bis(cholestery1) esters of dicarboxylic acids. Although these compounds are known,16-18 as are the related bis(cholestery1) carbamates and carbonate~,l~*~~ the optical properties of the cholesteric phases of these compounds have not been investigated before. In this paper a study of the Melting points, thermal phase transition temperatures and optical inspection of the liquid crystalline phases were deter- mined on samples between ordinary glass slides using an Olympus BH-2 polarization microscope equipped with a Mettler FP82HT hot stage, controlled by a Mettler FP80HT central processor. The selective reflection wavelengths were determined by measuring the transmission spectra of the chiral nematic phases of the compounds.For the pure compounds this was done as a function of temperature by inserting the hot stage with a planar oriented cholesteric sample between parallel glass slides in the measuring beam of a Hewlett Packard 8452A photo diode array spectrophotometer. The selective reflection wavelengths of 5 wt% solutions of the bis(cholestery1) esters in an approximately 1 :2 (w/w) mixture of cholesteryl nonanoate and cholesteryl chloride2' were deter- mined in the same manner at room temperature.Differential scanning calorimetry (DSC) thermograms were obtained on a Perkin Elmer DSC-7 system. The entropy changes at the phase transition temperatures are expressed as AS/R, in which AS is calculated from AS=AH/T. AH is calculated in J mol-' and T is the corresponding phase transition temperature in Kelvin. J. Muter. Chem., 1996, 6(9), 1469-1472 1469 Results and Discussion All compounds gave correct 'H NMR spectra, elemental analyses and single spots on thin layer chromatography The thermal transitions temperatures of the compounds are pre- sented in Fig 1 As can be seen the melting points show an alternating behaviour with spacer length This odd-even effect is more clearly observed for the N*-I transition temperatures of the compounds with n34 The compounds with odd n are monotropic liquid crystals, whereas the compounds with even n usually show enantiotropic thermal behavior Upon cooling below 160°C the compounds 1-3 and 1-1 crystallize before a liquid crystalline phase is found The compounds 1-2 and 1-0 have a broad enantiotropic liquid crystalline range and become isotropic at high temperatures These results indicate that the odd-even effects observed for the N*-I transition temperatures of the compounds attenuate with spacer length This behavior is often observed for twin liquid crystals 22 A problem encoun- tered with studying the liquid crystalline phases of compounds 1-0 and 1-2 is that the compounds slowly decompose above 200 "C Generally, odd-even effects for the liquid crystalline proper- ties of twin liquid crystals are more clearly expressed in the entropy change at the (chiral) nematic to isotropic transition temperature than the clearing temperatures themselves The AS/R values for the pure compounds that could be obtained by DSC are presented in Fig 2 As stated before, the values 0 0 D 0 012345678 n Fig.1 Melting points (---0 ---) and cholesteric-lsotroplc transitlon temperatures (-0-) of compounds I-n as a functlon of the number of methylene units (n)in the spacer 10-s u,.4 05-012345678 n Fig. 2 Entropy change (expressed as AS/R)at the cholesteric-isotropic transition temperature of compounds I-n as a funtion of n 1470 J Muter Chem, 1996, 6(9), 1469-1472 for 1-1 and 1-3 could not be obtained because the compounds crystallized before a liquid crystalline phase was found and the value for 1-0 could not be accurately measured due to severe decomposition For the compounds with an odd spacer the AS/R values lie around 0 6 and for compounds with even n they lie around 09 These values agree with those found previously for two members of this series" and are comparable with those of a series of cholesteryl o-cyanobiphenylyloxy- alkanoates,13 l4 and confirm the difference in ordering of the cholesteric phase as function of the spacer length When the number of flexible units in the spacer is even, the rigid mesogens preferentially adopt a parallel orientation in the nematic phase This gives better ordered nematic phases with higher isotropization temperatures and associated entropy changes than homologues with an odd number of flexible units in the spacer The orientation of the mesogens is dependent on the number of flexible spacer groups For n=even the cholesteryl groups are preferentially oriented parallel, whereas they are not parallel for n = odd These preferential orientations strongly affect the ordering and therefore the macroscopic properties of the cholesteric phase The molecules indhe cholesteric phase are present in a helical arrangement, and the pitch of the helix IS influenced by the ordering of the molecules in the phase This can be studied by measuring the selective reflection of light by the planar oriented cholesteric phase, because the wavelength of the reflected light in the liquid crystalline phase equals the pitch of the cholesteric helix Therefore measurement of the selective reflection wavelength can in principle give information about the ordering of the phase as a function of temperature, whereas measurement of AS/R only provides information about the ordering change at the isotropization temperature The selec- tive reflection wavelengths of the bis(cholestery1) esters are plotted in Fig 3 as a function of the reduced temperature T/T(N*-I) (both in Kelvin) The selective reflection wavelength strongly depends on the spacer length For odd spacers, the selective reflection wavelength increases with spacer length and is almost temperature independent For even spacers, the selective reflection wavelengths are larger than for compounds with an odd spacer Furthermore, contrary to what is found for the compounds with odd spacers, it decreases with tempera- ture It is clearly seen that the selective reflection wavelength exhibits a strong odd-even effect which attenuates with spacer length The results obtained correspond well with those obtained for other series of cholesterol containing twin and triplet liquid crystals l3 l5 For small odd n the selective reflec- tion wavelength decreases, but for n = 8 it increases again The reasons for this could be that the reflection wavelengths for the compounds with a longer spacer are determined at lower temperatures where, due to the temperature dependence, the selective reflection wavelength is higher and that upon increas- '-* \8ool700 600 400-1-7 ................300 '. '. . 1-5 ... 7 3 I * 1.. " Fig. 3 Selective reflectlon wavelengths of the cholesteric phase of compounds I-n as a function of the reduced temperature TIT (N*-I) ing the spacer the mesogens become more diluted, resulting also in a higher selective reflection wavelength. A small amount of a compound (guest) dissolved in a nematic host often induces a change in its properties that depends on the nature of the guest and is proportional to its concentration. Chiral compounds, for example, when dissolved in nematics induce cholesteric phases whose inverse pitch is proportional to its concentration.This interesting property has been the subject of much research.lP3 Also, the nematic- isotropic transition temperature of a mixture of nematics is often intermediate between those of the components. Because these relations hold best for mixtures of similar compounds and because the properties of the compounds with the shorter spacers could not be determined for the pure compounds, we also studied the thermal and optical properties of the bis(esters) as 5 wt% solutions in a liquid crystalline host consisting of a 2 : 1 (w/w) mixture of cholesteryl nonanoate and cholesteryl chloride.This host was also chosen because compounds I-n can be dissolved in them and because it forms a cholesteric phase at room temperature that reflects light in the visible range.21 The isotropization temperatures of these cholesteric mix- tures are depicted in Fig. 4. The host itself has an isotropization temperature of 78°C. Clearly an odd-even effect is seen that becomes more pronounced with a shorter spacer. In most cases the guest increases the isotropization temperature of the mixture. This is to be expected because the (chiral) nematic isotropic transition temperatures of mixtures usually lie between those of its pure components. The same trend in the odd-even effect is found as for the pure compounds.The stabilizing effect on the cholesteric phase of the host is stronger for the compounds with an even spacer than for compounds with an odd spacer and compound 1-1 even destabilizes the cholesteric phase of the host. Upon increasing the concen-tration of the guest the odd-even effects on the isotropization temperature become more pronounced. If a linear dependence is assumed between the clearing temperatures of the host and the guest, the clearing temperatures of the guest can be calculated. Upon comparing these with the observed values virtual clearing temperatures for compounds 1-1 and 1-3can be estimated of approximately 60 and 160"C, respectively. This corresponds nicely with the fact that no cholesteric phase could be observed for the pure compounds 1-1 and 1-3.It also confirms that the odd-even effect is more pronounced for compounds with shorter spacers.Previously, odd-even effects have been observed for mixtures 90 85 P 80 75 70 I I I I I 012345678 n Fig. 4 Cholesteric-isotropic transition temperatures ( +) of a 5 wt% solution of compounds I-n in a cholesteric host consisting of a 2 : 1 (w/w) mixture of cholesteryl nonanoate and cholesteryl chloride as a function of n 40 -20 -\E-4 d O---20 --40 -SO! 1I I I 1 I I I I I -10123456789 n Fig. 5 Induced change in selective reflection wavelength (AA/nm) at room temperature by a 5 wt% solution of compounds I-n in a cholesteric host consisting of a 2: 1 (w/w) mixture of cholesteryl nonanoate and cholesteryl chloride as a function of n in which a chiral compound was dissolved in a nematic host of which the chain length was changed.23 The better ordered phases of the host give mixtures with a longer pitch. For cholesteryl alkanoates in a compensated cholesteric mixture an odd-even effect was found for the temperature at which the phases are exactly compensated depending on the length of the alkyl chain of the guest.24 The effects are, however, weak and for other mixtures of a series of chiral compounds in nematics no clear odd-even effects on the pitch have been ob~erved.~' The influence of compounds I-n on the optical properties of the cholesteric host have also been studied.The host itself reflects at 650nm at room temperature and the selective reflection wavelengths of the solutions deviate from this value.These deviations are plotted in Fig. 5. For the series of com-pounds a clear odd-even effect is observed as a function of the parity of the spacer. For the compounds with an odd spacer there seems to be a minimum for n =5 and for the compounds with an even spacer this minimum lies at n =6. This may be the result of specific interactions between the guest and the host. Because the guest and host have the same left-handed screw sense of the helix the compounds that have the lowest selective reflection wavelength as a pure compound also give the lowest reflection wavelength as a solution. Most com-pounds decrease the selective reflection wavelength of the host. From Fig.3 it is seen that most pure compounds also have a selective reflection wavelength that is smaller than that of the host although it has to be realized that this was measured well above room temperature. Only compound 1-2 has a measured selective reflection wavelength that is higher than that of the host and in solution it also has a higher selective reflection wavelength than the host. Compound 1-0 increases the selective reflection even more, indicating that the pure compound would have a selective reflection wavelength that is in the near infrared. Very recently, a substantial difference in the pitch of the cholesteric and also the Sc* phase of two members of a chiral twin liquid crystal dissolved in an achiral host was observed.' In these twins the chirality stems from a chiral centre in the spacer and the different pitch was attributed to the odd-even effect of the guest on the ordering of the host.Conclusions A series of chiral twin liquid crystalline bis(cholestery1) alkane- dioates show odd-even effects as a function of spacer length for the properties of the cholesteric phase, i.e. the cholesteric J. Muter. Chem., 1996, 6(9), 1469-1472 1471 isotropic transition temperatures, the entropy change at this temperature and the selective reflection wavelength Compounds with an even number of flexible units in their spacers give the highest ordered phases with higher transition temperatures, higher entropy changes and higher selective 8 9 10 A Yoshizawa, Y Soeda and I Nishiyama, J Muter Chem, 1995, 5,675 A Yoshizawa, K Matsuzawa and I Nishiyama, J Muter Chem , 1995,5,2131 M K Koden, S Miyake, S Takenaka and S Kusabayashi, J Phys Chem 1984,88,2387 reflection wavelengths than compounds with an odd number of flexible units in their spacers Because the properties of several compounds with short spacers of the series could not be determined as a pure compound the properties of 5 wt% solutions of these compounds in a cholesteric host were also determined These solutions also exhibit odd-even effects for 11 12 13 14 R D Ennulat and A J Brown, Mol Cryst Liq Cryst 1971, 12,367 J L W Pohlman, W Elser and P R Boyd, Mol Cryst Liq Cryst 1973,20,87 A T M Marcelis, A Koudijs and E J R Sudholter, Reel Trav Chzm Pays-Bas 1994,113,524 A T M Marcelis, A Koudijs and E J R Sudholter, Lzq Cryst, the cholesteric isotropic transition temperatures and the selec- tive reflection wavelengths 15 1995,18,843 A T Marcelis, A Koudijs and E J R Sudholter, Lzq Cryst ,1995, 18,851 16 D Gross, Z Naturforsch ,1972,27b, 447 Mr A van Veldhuizen is thanked for recording the NMR spectra and Mr M van Dijk for performing the elemental analyses 17 18 19 J Rault, L Liebert and L Strzelecki, Bull Soc Chim Fr, 1975, 5,1175 E M Barrall 11, J F Johnson and R S Porter, Mol Cryst Liq Cryst, 1969,8,27 R A Vora and V R Teckchandani, Mol Cryst Liq Cryst, 1991, 209,279 References 20 R A Vora and V R Teckchandani, Mol Cryst Lzq Cryst , 1991, 209,285 1 G Solladie and R G Zimmerman, Angew Chem, 1984,96,335 2 G S Chilaya and L N Lisetski, Mol Cryst Liq Cryst 1986, 140,243 21 22 T D James, H Kawabata, R Ludwig, K Murata and S Shinkai, Tetrahedron, 1995,51,555 A Ferranni, G R Luckhurst and P L Nordio, Mol Phys, 1995, 85,131 3 L N Lisetski and A V Tolmachev, Lzq Cryst, 1989,5,877 4 G R Luckhurst, Macromol Symp ,1995,96,1 23 S Bualek, S Patumtevapibal and J Siripitayananon, Chem Phys Lett, 1981,79,389 5 G S Attard, R W Date, C T Imrie, G R Luckhurst, 24 H Baessler and M M Labes, J Chem Phys ,1970,52,631 S J Roskilly, J M Seddon and L Taylor, Lzq Cryst, 1994,16,529 6 H Ishzuka, I Nishiyama and A Yoshizawa, Liq Cryst, 1995, 25 N Emoto, M Tanaka, S Saito, K Furukawa and T Inukai, Jpn J Appl Phys, 1989,28, L121 18,775 7 A Yoshizawa and I Nishiyama, J Muter Chem ,1994,4449 Paper 6/02243J, Received 1st April, 1996 1472 J Muter Chem, 1996,6(9), 1469-1472

ISSN:0959-9428    

DOI:10.1039/JM9960601469

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Linear precursors of liquid crystalline thermosets Barbara Hirn," Cosimo Carfagna" and Rosa Lanzettab a Department of Materials and Production Engineering, University of Naples FEDERICO II, Piazzale Tecchio 80, 80125 Naples, Italy Department of Organic Chemistry and Biology, University of Naples FEDERICO II, Via Mezzocannone 16, 80134 Naples, Italy Polycondensation of glutaric acid with a diglycidyl terminated mesogenic molecule [p-(2,3-epoxypropoxy)-a-methylstilbene]was carried out with a basic catalyst. A variety of novel main chain thermotropic liquid crystal oligoesters were synthesized uia a short melt-copolycondensation process, by using different ratios of co-monomers. Preliminary studies by thermogravimetric analysis, differential scanning calorimetry, steric exclusion chromatography and Fourier transform infrared spectroscopy have been carried out on the reacting mixtures in order to optimize the reaction conditions (temperature, time).Carbon-13 nuclear magnetic resonance was used to identify the material structure. The mesophase stability ranges of the oligoesters were evaluated by means of DSC and optical polarizing microscopy. X-Ray diffraction analysis was applied to determine the nature of the mesophase. Crosslinking of glycidyl-terminated rigid rod monomers with various curing agents produces liquid crystalline thermosets with outstanding The chemistry of the curing reaction is not far from that described in literature and regarding conventional epoxies. Of course, the density and distribution of the crosslinks in the network, as well as the kinetics of the reaction, are affected by the level of order of the growing thermosets.It has been found that aromatic amines react with epoxy mesogens very quickly, producing nematic On the other hand, aliphatic diacids react much more slowly, giving smectic elastomers that can be subsequently oriented by means of a stress field.899 As in the case of conventional epoxies, it should be interes- ting to explore the possibility of synthesizing functionalized linear prepolymers from liquid crystalline epoxies that could be further cured. In this way, by balancing the length of the prepolymers with the amount and the type of curing agent, it should be easy to produce thermosets with the desired levels of order and transition temperature for different applications. One of the ways to synthesize these prepolymers is the polymerization reaction of a dicarboxylic acid with a diglycidyl endcapped mesogenic molecule. The reaction of the epoxy ring with a carboxylic acid presents several advantages.lO"' It can be carried out at moderate temperature (80-150°C) in the presence of basic catalysts [Scheme l(a)].It is an addition reaction from which no volatile compound is eliminated, so formation of bubbles in the material is avoided. Another advantage of this polymerization process is the formation of polymers containing hydroxy side groups, which can be very useful for further chemical modification of the polymer chains, such as grafting or crosslinking.However, there are three different undesirable side reactions [Scheme 1 (b)].In order to eliminate these reactions and obtain linear polymers containing hydroxy side groups, the polymeriz- ation must be base-catalysed. In a first step, a carboxy anion is formed (Scheme 2) and the reaction proceeds ionically through the epoxy group. The acid anion is then regenerated. For example, in the presence of a tertiary amine, if the carboxylic acid is introduced in excess in the reaction medium, the polymerization reaction stops when all of the epoxy is consumed; the resulting polymers are carboxy terminated, and these functions cannot react further with the pendant hydroxy groups of the main chain because of the presence of basic catalyst. In order to obtain semi-flexible linear liquid crystalline polyesters which contain hydroxy side groups and carboxy terminated, a bulk polycondensation of different mixtures of glutaric acid (GA) and of p-( 2,3-epoxypropoxy)-a-methyl-stilbene (DOMS) in the presence of N,N-dimethylbenzylamine (BDMA) were carried out.By varying the co-monomer ratios a new class of products was generated. Experimental Measurements Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and thermomechanical analysis (TMA) of all samples was performed by means of an integrated analytical system DuPont 2100 composed of the following modules: differential scanning calorimetry (DSC) 2910, thermogravi- metric analyser (TGA) 951, and thermomechanical analyser (TMA) 2940.The X-ray diffraction patterns were recorded by the photographic method with a Rigaku model III/D max generator by using Ni-filtered Cu-Ka radiation. The textures of the crystalline and liquid crystalline phases were observed in transmitted light with an optical microscope (Reichert-Jung Polyvar), equipped with crossed polarizers for polarised microscopy (POM). The temperature was controlled by means of a Linkam TH 600 hot stage apparatus. Fourier transform infra-red analysis (FTIR) was performed with a Nicolet 5PC spectrophotometer. The 13C NMR spectra of the oligomers were obtained on a Bruker 100MHz in FT mode in [2H,] DMSO at 30 "C. The signal integrations were obtained by an Inverse-Gated experiment performed with a delay of 150 s.Steric exclusion chromatography (SEC) was performed by means of an apparatus composed of a Refractive Index detector (Shimadzu Rid-6A), an HP+C pump (Varian 2510) and three columns ( lo3, 500 and 100 A). Synthesis of monomers The diglycidyl endcapped compound used in all polymerization reactions was p-( 2,3-epoxypropoxy)-a-methylstilbene(DOMS). The synthesis was previously described in the literature;8 mp 130"C, T,N115 "C (monotropic). Glutaric acid (GA) (99%, mp 95-98 "C) and N,N-dimethylbenzylamine (BDMA) (99%, bp 183-184 "C) were purchased from Aldrich and util- ized without any further purification. Their purity was checked by DSC. J. Mater. Chew., 1996, 6(9), 1473-1478 1473 HOC(CH2)3COH + \-CH20-@zCH-@XH2-/ -II II 0 -0 00 GA DOMSI BDMA t C(CH2)3COCH2CHCH20 ~~~CH~OCH2CHCH20 II II I I0 0 OH OH (b 1 estenfication via hydroxy groups of the main chain -+ HOC--roc-+ H20II oc-II0 II 0 hydration of epoxy groups + H20 vT HO HO ethenfication reaction of epoxy with hydroxy groups I OH Scheme 1 (a)General scheme of polyesterification reaction, (b)side reactions base --co-II0 - +T -COCH*CH-II I0 0- -COCH2CH-II I0 0- + -COH II 0 --COCH2CH-II I0 OH + -CO-II 0 Scheme 2 Initiation of polyestenfication reaction Synthesis of oligomers The reagents p-(2,3-epoxypropoxy)-a-methylstilbene(DOMS), glutaric acid (GA) and BDMA (10mol%) were blended and heated at 140°C After 20 min, the reaction mixture was pressed between two glass plates (previously treated with a surfactant, Surfasil@) and heated for another 20 min at 140 "C The ratio GA DOMS varies from 1 1 to 12 1 and the synthesized oligomers were indicated as DG1 A, DG105A, DG1 1A and DG1 2A The resulting films were studied by TMA, DSC, SEC, osmometry, X-ray diffraction, POM and I3C NMR spectroscopy Results Preliminary studies of the polycondensation reaction Preliminary studies of the reaction parameters of the polymer- ization process were carried out by TGA under air The weight 1474 J Muter Chem, 1996, 6(9), 1473-1478 loss percents determinated by TGA during the polymerization reaction at 140 and 180°C of the blends (DOMS-GA) with and without basic catalyst are presented in Table 1 DSC analysis (Fig 1)of the mixtures (DOMS-GA-BDMA) consists of a heating from 30 to 140"C, followed by an isotherm at 140 "C (Fig 1) During the heating step the melting endotherms characteristics of both GA (110 "C) and DOMS (130 "C) are well evidenced The exotherm present during the isotherm at 140°C is representative of the polymerization process of GA with DOMS In all cases, after 15 min, the reaction is completed Analysis of polymerization reaction of the blend DGlA The FTIR analysis of the reaction medium during the polymer- ization of the stoichiometric blend shows an increase in the absorbance at 3600-3200cm-' due to the formation of side hydroxy groups resulting from the addition reaction of epoxy and carboxy groups (Fig 2) During the reaction, the CO,H equivalent is determined by Table 1 Thermogravimetry analysis of blends (GA-DOMS) with and without basic catalyst composition DOMS-GA-BDM A/mol 110 1120 11 01 11201 T/OC weight loss (%) 140 67 180 88 140 91 180 92 140 17 180 49 140 28 180 71 0.5-7 I 0, P O-O-6= ri; -0.5-a,.c -1 .o-34100 32bo 3b 28100 wavenurnber/cm Fig.2 FTIR analysis of the blend DGlA during the polymenzation reaction titration using a solution of 0.1 mol dm-3 NaOH in the presence of phenolphthaleine as indicator (Fig. 3). The DSC analysis was carried out after 2, 5,10, 15 and 20 min of reaction (Fig. 4). For increasing reaction times, the endotherm moves towards lower temperature, and disappears after 20 min.This trend could be explained on the basis of the following consider- ations. During the early stages of the reaction, the endotherm is the result of the melting of the growing oligomers and unreacted monomers. With increasing time, the monomer is consumed and prepolymer is no longer crystalline, at least for the samples cooled from the reacted mixtures. 4.5-'' ' ' ' ' ' ' ' ' ' ' ' " " ' ' ' ' '. --4 ----0.5 i i iI I I I 1 I I I 1 I I I I I I 17 I 11 1 7 I:-Os4-= +-([I2 -0.8--1.2 I I 1 Molecular weight and functionality of the oligomers The weight of all prepolymers was determinated by osmometry and by SEC. The C02H equivalence per gram of product was evaluated by titration using a solution of 0.1 mol dme3 NaOH in the presence of phenolphthaleine as indicator. Both param- eters allow the evaluation of the functionality (Table 2). The osmometry was carried out at 90°C in DMF, and the SEC was performed at 20°C in THF.The signal integration of NMR spectra (Fig. 5) allows the determination of [OH]/[CO, R] and [OH]/[C02 H] ratios. The OH equivalence per gram of product was therefore calculated from the COzH equivalence per gram obtained previously by titration (Table 3). Thermal behaviour of the oligomers In order to determine all phase transition temperatures, all prepolymers were submitted to a DSC analysis consisting of a first heating made at a rate of 10"C min-l [Fig.6(u)] followed by a cooling at a rate of 15"Cmin-' in order to inhibit the crystallization of the oligomers [Fig. 6(b)],and by a second heating at a rate of 5 "C min-' [Fig. 6(c)] selected to enhance the sensitivity of the DSC technique (Table 4). Mesophase characterization X-Ray diffraction patterns of the crystalline oligomers were recorded at room temperature on samples quenched from the isotropic phase (Fig. 7) and allowed to crystallize at room corresponding to a spacing of 12.8 A. The weak reflections appearing at wider angles are probably due to the onset of crystallization of the quenched sample. In the pattern recorded for the crystallized sample, more crystalline reflections appear. that the mesophase developed during quenching is of the smectic type, the spacing corresponding to the distance between two adjacent smectic layers.The analysis of the texture as revealed by POM analysis confirms the X-ray diffraction analysis, even if the high viscosity of oligomeric compounds does not allow the observation of focal conics or a perfectly defined texture (Plate 1). Roviello and Sirigu reported the mesomorphic behaviour of some aliphatic esters of dunng the polymenzkon of DG1A-therefore a tilt within the layers could be supposed. J. Muter. Chem., 1996, 6(9), 1473-1478 1475 Table 2 Weights and functionality of the oligomers SEC functionality oligomers osmometryMJg mol-' Mn" MW" Ib CCO,Hl(equiv g- C d ~~~~~ DG12A 2280 2453 8044 33 122 x 10-3 28 3 DG11A 2873 2896 9275 32 728 x 10 21 21 DG105A 3448 2815 8198 29 5 56 x 10-4 19 16 DGlA 3363 3665 12209 35 5 98 x 10 2 22 "In equivalent PS bI = Mw/Mn=index of polydispersity 'Functionality calculated from the osmometnc values dFunctionality calculated from SEC values Fig.5 13C NMR spectrum of DGlA Table 3 Determination of the OH equivalence per gram from the I3C NMR spectrum' oligomer ~~ [OH]/[CO,R] [OH]/[CO,H] [OH]/equiv g-' DG12A 07 21 2 52 x 10-3 DG11A 08 5 3 6 x loW3 DG105A 08 46 26 x 10-3 DGlA 07 54 3 2 x 10-3 Discussion The preliminary isothermal studies by TGA at temperatures of 140 and 180 "C (under air) of different blends of DOMS-GA without BDMA (Table 1)show that the weight loss percentage increases with the temperature and with the increasing excess of dicarboxylic acid present in the mixture The weight loss is representative of the extent of the esterification side reaction of carboxylic acid with the hydroxy groups of the main chain oligomers (Scheme 1) In the presence of basic catalyst, the weight loss is lower because the esterification reaction of the carboxylic acid and epoxy groups prevails, and after complete consumption of epoxy groups the end carboxylic groups of the synthesized oligomer do not react with the side hydroxy groups to any great extent, at least at 140 "C According to the literature," it can be noted that the presence of a basic catalyst and a decrease in the reaction temperature avoided the undesirable side reactions On the other hand, an increase of the co-monomer ratio [GA]/[DOMS] from 1 to 12 promoted the reaction of carboxylic acid with the hydroxy groups of the main chain oligomers In the case of the stoichiometric blend GA-DOMS, the analysis by FTIR, SEC and DSC and the determination of the C02H equivalence per gram of the reaction medium dunng the polymerization process allow verification of the simultaneous and total consumption of the co-monomers, the increase of the growing chain weight, the 1476 J Muter Chem, 1996, 6(9), 1473-1478 -0.7 I 2'0 do Id0 140 '9 08-Iul a OA-6 E c.04-c 0 2-0.d A0 2'0 &I Id0 140 -0.d -20 2b tib Id0 140 T/"C Fig.6 DSC analysis of the final oligomer, (a) first heating, (b)cooling, and (c) second heating formation of hydroxy groups and the reduction of the carboxylic group concentration The molecular weights of the synthesized oligomers deter- mined by osmometry and SEC (Table 2) are relatively low (2300-3400) and weakly affected by the variation of the co- monomer ratios The high values of the ratio M,/M,, (Table 2) indicate high polydispersity for the final products, probably resulting from the high values for the blend viscosity, but also possibly due to partial crosslinking via some of the numerous side reactions In the case of bulk polymerization, the increase of viscosity is one of the limiting parameters of the polymer Table 4 Phase transition temperatures and enthalpies determined by differential scanning calorimetry first heating second heating cooling oligomer TK ,LC I"C AHILLCIJ g-' TLc,1/3c AHLCSIJ g- T,LCI3C T,/T TLC,II0C AHLCJIJ g- DG1.2A 44.4 10.5 106.2 10.4 97.9 26.1 102.0 6.6 DG1.1A 41.3 9.3 126 10.8 112.4 21.9 123.3 11.8 DG1.05A 41.9 9.2 131.8 14.1 119.3 24.3 131.4 10.8 DGlA 41.7 8.7 123.3 6.4 118.1 26.4 127.4 8.8 Fig.7 X-Ray of quenched DGl.lA, room temperature Fig. 8 X-Ray of crystalline DGl.lA, room temperature chain growth and of the molecular weights of the resulting products. In our case it is not possible to carry out the polymerization at higher temperatures since an increase of temperature implies a growth of undesired side reactions. According to the literature, higher molecular weights could be obtained by polymerizing diglycidyl endcapped monomers with the proper dicarboxylic acid in an organic ~olvent.'~,'~ The functionality of the oligomers (Table 2) was determined Plate 1 POM of DGl.lA, T= 1OOT from both molecular weight and CO,H equivalence per gram.The values of this parameter increase with the excess of glutaric acid introduced into the reaction medium. This result confirms the preliminary TGA analysis showing the crucial influence of co-monomer ratios on the esterification side reaction of the carboxylic groups with the side hydroxy of the growing chains, forming branched or crosslinked polymers.The DG1.2A has a functionality of three but is soluble in organic solvents (THF, DMF, DMSO etc.), so for this reason it is reasonable to hypothesize that it is not a cured product but a branched one. 13C NMR spectra show that the resulting prepolymers were not completely linear because the integration of the signal characteristic of the ester groups (6 172.5) is higher than the corresponding value of the carbon bonded to the hydroxy group (6 66.8) (Table 3). This result also confirms that some part of the hydroxy side groups of the prepolymer main chain are involved in secondary reactions. 13C NMR spectra allow the determination of the OH equivalence per gram of prepolymers, which can be very important in the case of a further curing reaction.The synthesized oligomers crystallize at room temperature but the crystallization can be inhibited by a quick cooling to give glassy products (T, of around 25 "C) which slowly crys- tallize at room temperature (Table 4). The TKqLCwas found to be in the range of 40-45"C, and the corresponding TLc,,was found to be in the range 100-130 "C. The high values of the J. Mater. Chem., 1996, 6(9), 1473-1478 1477 isotropization enthalpies (6-14 J g-') strengthen the pre-viously discussed hypothesis that the mesophase exhibited by the prepolymer is of the smectic type, even if the AH values cannot be considered conclusive The relatively wide range of the liquid crystalline phase denotes the high stability of the smectic structure, which might be a consequence of interchain hydrogen bonds Conclusion A variety of novel thermoplastic liquid crystal carboxy- terminated oligoesters containing hydroxy side groups was synthesized vzu a short melt-polycondensation of a dicarboxylic acid and a diglycidyl mesogenic molecule, in presence of a basic catalyst These products were crystalline at room tem- perature The crystallinity can be inhibited by quenching the melt to get glassy products with a 5 of 25°C The liquid crystalline phase of these products was smectic and proved stable over a relatively wide temperature range (80-100 "C) Their molecular weights decrease from 3400 to 2300 with the increase of the acid content in the blend The functionality of the oligomers was equal to or higher than two, and the OH equivalence per gram of product was lower (2 5 x to 3 6 x than the theoretical value (4 x because of OH participation in secondary reactions The presence of these hydroxy side groups made these oligoesters potential candi- dates as precursors for liquid crystalline thermosets References 1 G G Barclay, C K Ober, K I Papathomas and D W Wang, J Polym Sci ,Polym Chem ,1992,30,1831 2 G G Barclay,S G McNamee,C K Ober, K I Papathomasand D W Wang, J Polym Sci, Polym Chem, 1992,30,1845 3 C Carfagna, E Amendola, M Giambenni, A Filippov, and R S Bauer, Liq Cryst, 1993,13,571 4 C Carfagna, E Amendola and M Giambenni, Compos Struct , 1994,27,37 5 C Carfagna, E Amendola, M Giamberini and A Filippov, Macromol Chem Phys , 1994,195,279 6 C Carfagna, E Amendola and M Giambenni, Macromol Chem Phys , 1994,195,2307 7 E Amendola, C Carfagna, M Giambenni and G Pisaniello, Macromol Chem Phys , 1995,196,1577 8 M Giambenni, E Amendola and C Carfagna, Mol Cryst Liq Cryst, 1995,266,9 9 C Carfagna, E Amendola and M Giamberini, Makromol Chem , Rapid Commun , 1995,16,97 10 H Lee and K Neville, in Epoxy resins, their applications and tech- nology, McGraw-Hill, NY, Toronto, London, 1957 11 P J Madec and E Marechal, in Aduances in polymer science, Springer-Verlag, Berlin, 1985, vol 71 12 A Roviello and A Sirigu, Gazz Chim Ital, 1977,107, 333 13 E Haertel, M Fedtke, D Pospiech and H Gulbe, Plaste Kautsch , 1984,31,405 14 F B Jones, USP 3,639,655, 1972 (Chem Abstr ,1972,76, 141 764) Paper 6/02795D, Received 22nd April 1996 1478 J Muter Chem, 1996, 6(9), 1473-1478

ISSN:0959-9428    

DOI:10.1039/JM9960601473

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Liquid crystal polymers copolymers and elastomers containing a laterally attached mesogenic unit Eric A. Whale, Frederick J. Davis* and Geoffrey R. Mitchell Polymer Science Centre, University of Reading, Whiteknights, Reading, UK RG6 2AD The synthesis of a closely-coupled laterally attached side-chain liquid crystal polymer is described. The material exhibits liquid crystalline behaviour over a wide temperature range. Incorporation of non-mesogenic methyl acrylate as a comonomer with the potentially mesogenic monomer results in copolymers which are liquid crystalline, even when the non-mesogenic portion exceeds 60 mol%. Macroscopic alignment can be readily realised in both homopolymer and copolymer samples, either using a magnetic field or by pulling as fibres, and X-ray scattering shows the level of global orientation to be relatively high.Copolymerisation of the mesogenic unit with ca. 10 mol% of hydroxyethyl acrylate results in materials which can be cross-linked by reaction with a diisocyanate. The application of mechanical stress to liquid crystalline elastomers based on this closely coupled unit results in some global orientation of the mesogens, and the stress-strain-orientation behaviour of this cross-linked system is described. Both copolymers and elastomers are compared with liquid crystal polymers in which the mesogen is attached via a terminal linkage. Typically, side-chain liquid crystal polymers are built up from a mesogenic unit, usually consisting of two or more aromatic units, and a polymer backbone, of which acrylate, methacrylate, and siloxane are the most commonly employed.lP2 The two components are connected via a coupling chain or flexible spacer, generally containing two or more methylene group^.^ In the majority of cases the mesogenic unit is attached to the coupling chain terminally (i.e.as a para substituent on one ring), but a number of variations to this geometry have yielded liquid crystalline polymers; for example, discotic system^,^ and lateral liquid crystalline polymers, where the mesogenic unit is linked through the mid-point rather than term in all^,^-^ have been prepared. It is a material with this latter geometric arrangement which forms the basis for the investigations described in this presentation.Most examples of lateral liquid crystal polymers retain the requirement for a flexible spacer to decouple the motion of the mesogen from the polymer ba~kbone.~.~,' An interesting vari- ation on laterally attached polymers has been described, how- ever, in which the mesogen is bonded very closely to the polymer backbone; i.e. the coupling chain is small. Such materials have been labelled by Zhou as 'mesogen jacketed' liquid crystal polymers.'-" Of particular interest is the existence of a liquid crystal phase in a polymer where there is substantial coupling between the mesogen and the polymer backbone, such that the motion of the two units are strongly dependent. The mesogen jacketed model implies that the mesogenic moieties are not just the side-groups, but rather the polymer as a whole; such materials may be considered as intermediate between side-chain and main-chain liquid crystal polymers.'2 As part of our continuing investigations of coupling in liquid crystal polymers and ela~torners,~*'~-'~ it was decided to investi- gate further the mesogen jacketed model of Zhou.In the first part of this account we describe the effect of diluting the mesophase by the incorporation of non-mesogenic moieties along the polymer backbone, and compare the results with similar experiments for liquid crystal polymers with terminally attached mesogenic It was of particular interest to determine if the flexibility of the polymer backbone had a marked influence on the phase behaviour of such materials.In the case of the 'mesogen-jacketed' model of Zhou,'.'' it is clear that the formation of a liquid crystal phase requires that the polymer backbone adopts an extended chain conformation; presumably such a conformation relies on the rigidity imposed on the system by the extreme bulk of the side-groups. It might be expected that the addition of a high enough concentration of non-mesogenic comonomer units will provide the polymer backbone with sufficient flexibility to completely disrupt the liquid crystal phase. In the second part of this account the behaviour of some liquid crystalline elastomers based on the closely-coupled, laterally-attached mesogen is described. These studies have focussed particularly on the phase behaviour and the mechan- ical behaviour of the materials.In this way it was intended to determine the influence of close coupling between the meso- genic unit and the polymer backbone on the magnitudes of the effects typical observed in such elastomers.'' Synthesis Monomer synthesis was undertaken using a modification to the method given by Zhou:','' anisoyl chloride was reacted with 2,5-dihydroxybenzaldehydeto produce 2,5-bis( 4-methoxy- benzoyloxy) benzaldehyde I; R I R=CHO II R=CH20H = ""'OP0 this was then reduced to 2,5-bis( 4-methoxybenzoyloxy) benzyl alcohol I1 with BH3. THF followed by esterification to produce the monomer 111. The modification was necessitated by the observation that the reported reduction of the aldehyde, using NaBH, in DMSO, was found to give an unexpected product.Spectroscopic analysis (see Experimental section) shows this is either IV or V, MeIV Me v J. Muter. Chem., 1996, 6(9), 1479-1485 1479 i 1 I I I I I I I I I 907 6 5432 1 0 GJPPm Fig. 1 NMR spectra of (a) the expected product from the synthetic pathway described in the text, and (b) the product obtained on following the procedure listed in ref 10 in which complete reduction of the aldehyde to the methyl group has occurred, together with cleavage of one of the ester units, such a process is not untypical of reductions in DMSO and related media,20 however, although the similanty in the predicted NMR spectra of these two isomers does not allow an unequivocal assignment to one or other, it would appear that one of the two isomers is formed exclusively, this suggests that electronic influences may be important It should be noted here that the NMR spectrum quoted by Zhou for the appro- priate intermediate' ''is clearly not that of the alcohol claimed (Compound 11), but rather that of either IV or V,+ a similar spectrum for this unidentified compound was obtained in this work and this is shown together with the 'H NMR of the alcohol I1 in Fig 1 Polymerisation of the acrylate of IV (V) gives a compound with no mesophase In spite of the contradictory NMR evidence cited, the polymers described' lo bear close similarity, in terms of their phase behaviour, to the liquid crystal polymers described below, furthermore it is clear that, more recently,21 Zhou has recognised over-reduction by sodium borohydride in DMSO to be a problem, and has found that this can be overcome by the complete removal of water from the solvent, unfortunately, this precludes the addition of the reducing agent as an aqueous solution We believe the procedure described in this presen- tation to be superior, since it is both clean (with almost complete absence of any side-products) and relatively rapid, furthermore, as the starting material is only poorly soluble in tetrahydrofuran, the gradual disappearance of this material as the more soluble alcohol is produced provides a clear indication of the extent of reaction In order to establish the most likely product of the sodium borohydride reduction, and in particular the site of ester cleavage, a small scale reduction in (CD,),SO was undertaken on the 4-methoxybenzoate esters of ortho-and meta-hydroxy- benzaldehyde, and probed by 'H NMR It was found that for ?The differences in the predicted NMR spectra of IV and V are minimal and it is not possible to distinguish these materials from the NMR data alone the meta isomer, the aldehyde was reduced to the benzylic alcohol in good yield In contrast, for the ortho derivative, a mixture of products was obtained, most notably, 2-methyl- phenol These observations clearly support the exclusive cleav- age of the ester unit ortho to the aldehyde, leading to the formation of IV rather than V Polymers and copolymers were prepared by free radical polymerisation of the acrylate monomer I11 with varying proportions of the required comonomer In the first part of this account, copolymers with methyl acrylate were prepared (this being chosen such that the comonomer would disrupt the polymer backbone without introducing additional steric complications from the side-group), for the production of the elastomers described in the second part of this contribution, a small proportion of hydroxyethyl acrylate was added to allow subsequent cross-linking with a diisocyanate (see Experimental section) The majority of the polymers were prepared in THF with 4 mol% AIBN, to maximize conversion Where higher molecular weights were required, chlorobenzene was used as a solvent (to minimise chain-transfer reactions) and the AIBN concentration was reduced to 1 mol% Results and Discussion Copolymers Composition of copolymer systems.The final composition of polymers from the initial feedstock, determined from NMR spectroscopy, (together with the molecular weight data evalu- ated by GPC) are detailed in Table 1 From this, it can be seen that the uptake of the two monomers into the final polymer is as expected on the basis of their concentration in the initial feedstock This is consistent with the monomers forming random copolymers,22 z e that both acrylates exhibit similar kinetic behaviour This was confirmed by a senes of experi- ments in which the composition of polymers of both L50 and L80 were monitored with time, it was found that the composi- tion of the polymer remained invariant as the polymerisation proceeded and at no stage was there any preference for one or other monomer Molecular weight.The relatively low values for the molecular weight obtained from most samples reflect two factors, firstly the unusually high initiator concentration, and secondly, the influence of the polymerisation solvent, tetrahydrofuran is known to act efficiently as a chain transfer agent 22 However, this mode of termination is not responsible for the unusually narrow molecular weight distribution in these samples, it is likely that the rather narrow polydispersity arises from the removal of a substantial fraction of lower molecular weight material during the purification procedure Phase behaviour.The phase behaviour of the copolymer samples was measured by DSC and optical microscopy The Table 1 Composition of polymers synthesised feedstock composition methyl acrylate methyl acrylate Mwl yield sample I11 (mol%p I11 (mol%)b M,' M, D,d (%) L10 10 90 16 84 82x103 14 66 10 L20 20 80 23 77 9Ox1O3 13 56 20 L35 35 65 35 65 1 52x104 16 70 15 L40 40 60 39 61 99x lo3 12 42 40 L50 50 50 50 50 148x lo4 13 53 60 L60 60 40 60 40 1 18~10~11 38 70 L80 80 20 80 20 109x lo4 12 28 75 LlOO 100 0 100 0 457x 104 15 28 75 HLlOO 100 0 100 0 457x lo4 16 99 75 a Initial feedstock added Composition calculated from 'H NMR M, determined from GPC D, =degree of polymerisation 1480 J Muter Chem, 1996,6(9), 1479-1485 behaviour observed was broadly in line with expectations on the basis of similar copolymer sy~tems;'~ the transition temp- eratures are shown in Fig.2. As inspection of this figure shows, the glass transition temperature declines steadly as the concen- tration of methyl acrylate is increased, indicative of a rather more flexible polymer backbone. This increased flexibility is not accompanied by complete disruption of the mesophase except at relatively high methyl acrylate concentrations. The liquid crystal phase is able to tolerate a rather high concen- tration of non-mesogenic diluent. This possibly reflects the shear bulk of the mesogenic unit, and the wide temperature range over which a liquid crystalline phase can be observed for the homopolymer.X-Ray scattering. Samples of the mesogenic material with a macroscopic director alignment could be readily prepared either using magnetic fields (typically a field of 0.6 T applied for 18 h was sufficient to induce alignment) or by pulling as fibres. X-Ray scattering measurements were made on aligned samples of these copolymer systems using procedures described e1~ewhere.I~In all cases the aligned samples gave scattering curves typical of an aligned nematic polymer. For the fibre samples, the long axis of the mesogenic units lay parallel to the draw direction in all cases. The X-ray scattering curves all showed two main peaks along the equatorial directiono (i.e. normal to the alignment axis), with a maximum at ca.1.25 A-', arising from cor!elations within the mesogenic units, and a peak at ca. 2.8A-1 which became more prominent as the mesognic concentration decreased. This latter peak is typical of simple polymer systems based on polyacrylates. The increased prominence reflects the greater concentration of chains per unit mass for these samples. However, it is clear that the packing of mesogenic units remains relatively unaffect- ed, even by large changes in the polymer composition. Fig. 3 shows the global orientation parameter,23 measured at room temperature for a series of fibres prepared by drawing at temperatures in the liquid crystal phase followed by rapid cooling. Although pulling fibres was rather difficult owing to the unexpectedly high viscosity of the liquid crystal phase (particularly in view of the relatively low molecular weight of these materials), such samples gave consistently higher orien- tation parameters than observed for similar samples prepared using a magnetic field.The figure shows that relatively high degrees of macroscopic alignment are possible for all the samples which exhibited a liquid crystal phase. The slight decrease in the parameter (P2) at higher concentrations of methyl acrylate suggests less ordered structures, and such behaviour is typical of copolymer systems involving non-mesogenic m~nomers.'~J~ Elastomers Cross-link density. Both swelling and mechanical measure- ments were used to estimate the cross-link density of the elastomeric samples using established procedures.22 For the 180~ *Ot Fig.2 Plot showing the phase behaviour of copolymers of III with methyl acrylate as a function of composition 0.6 0.5 - 0 0 0 0 0.4 - 0 h v0.3 a" -0.2 1 O.' tt 01 4.I I I I 0 20 40 60 80 100 mol% of 111 Fig. 3 Measured global orientation parameter (P2)at s= 1.25 A-', for samples aligned as fibres, as a function of the mesogenic unit concentration swelling measurements the cross-link density was obtained using the Flory-Huggins parameter for a similar system in which the same aromatic unit is connected to an acrylate backbone by a longer coupling-~hain.~~ The data obtained are shown in Table 2. The HEA6 sample had rather poor mechan- ical properties and was found, from the swelling measurements, to have a rather high sol content (50% compared to 6% for the HEAlO sample) in keeping with the lower molecular weight of the precursor polymer.The discrepancy in the cross-link density for the HEAlO sample obtained from the two methods we believe to reflect inaccuracies in the procedures, which are particularly large for the swelling experiments (approximate errors being ca. 60% for swelling measurements and ca. 20% for the mechanical measurements). Phase behaviour. In keeping with observations of other nematic elastomers, such as those based on the monomer VI,16 cross-links can be introduced into the system without substan- tial disruption of the nematic phase, although some changes in the phase transition temperatures are observed as shown in Table2.The particular feature of interest in this data is the behaviour of the HEAlO sample, which showed a substantial decrease in the nematic-isotropic transition temperature when cross-linked in the liquid crystal phase. Theoretical st~dies,~~?~~ since bourn out by e~periment,'~?~~ have shown that cross- linking a liquid crystalline polymer in the liquid crystalline phase should produce a stabilisation of that phase. Where deviations from this behaviour have been observed28 they have been attributed to non-equilibrium behaviour. VI In particular for systems based on VI where n is small, it is apparent that, because of the rather rigid polymer backbone, the cross-linking reaction occurs too rapidly to allow the polymer backbone to reach an equilibrium structure. It seems likely that the polymer system descibed here behaves in a similar way.Mechanical behaviour. As with other liquid crystalline elasto- mers, the mechanical behaviour of these materials in the isotropic phase was similar to that expected for a conventional elastomer. Any effects arising from the proximity of the liquid J. Muter. Chem., 1996, 6(9), 1479-1485 1481 Table 2 Properties of copolymers of I11 with hydroxyethyl acrylate and elastomers formed from these polymers sample 6% HEA 67 148 1.79 x 104 40 1.2 6% HEA-CLf 74 151 6.37 x 104' 1.4%' 23' 10% HEA 93 171 5.34 x 104 125 1.9 10% HEA-CL' 85 158 4.13 x 104h 1.03h 21h 7.06 x 104' 0.6' 12' a Tg measured at mid point.Error of 2 1 "C. TN-, measured from peak maxima. Weight average molecular weight measured using GPC. D, =degree of polymerisation. XL-D =cross-link density. XL-E' Measured from swelling experiments. crystalline phase25 could not be observed due to the high temperatures and the poor mechanical properties of the samples at these temperatures. In the nematic phase a rather more complicated stress-strain curve was obtained. A typical example is shown in Fig. 4.Similar curves have been observed for other elastomer ~amples~.~~.~~ and the unusual behaviour arises as a consequence of global alignment of the mesogenic unit^,'^'^^ which may be considered to increase the effective sample length, as the stress is increased." The stress-strain curves obtained from a liquid crystalline elastomer in the liquid crystalline phase reflect the relative ease with which alignment processes are possible.In order to gauge the extent of side-chain alignment, in situ X-ray scattering experiments were performed on samples extended in the liquid crystalline phase. The macroscopic orientation was measured after allowing sufficient time for its development (time depend- ence measurements of the level of orientation shows that the maximal orientation occurred after about 20 min; after this time at constant strain a slight decline was noted, presumably due to imperfections in the network). A typical plot of orient- ation as a function of extension is shown in Fig. 5.The plot correlates well with the stress-strain plot shown in Fig. 4 as discussed below (although these latter data were obtained from a dynamic experiment) and is in agreement with data obtained from terminally attached liquid crystalline polymers based on the acrylate VI.30 The orientation measurements shown in Fig. 4 provide a general picture of the processes occurring as the elastomer is extended. The rather high initial stress required reflects the energy needed to disrupt the local orientation of the mesogens in the polydomain structure. As the extension is increased less strain is required due to the global alignment of these mesogens; finally, any further extension requires the disruption, albeit temporarily, of the monodomain structure. The main difference between the behaviour of these samples and those of more loosely coupled systems is the rather low levels of orientation 2o l5 t OKOO 1105 1110 11.15 1120 1l.25 1130 1.95 extension ratio Fig.4 The measured mechanical behaviour of 10% HEA-CL at 120°C.Data obtained after sample was allowed to relax to an equilibrium stress value. 1482 J. Muter. Chern., 1996, 6(9), 1479-1485 =cross-link efficiency. Determined estimated error0.~~1I Oe20t 0.1540.101 0 from mechanical measurements. 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 extension ratio Fig. 5 Plot of orientation parameter (P2) as a function of extention for the sample 10%HEA-CL (at 105"C).The data was obtained after allowing complete relaxation of the sample to provide an equilibrium orientation. achieved, with orientation parameters only half those found for a terminally attached ~ystem,'~ and furthermore, lower than when the samples were prepared with a magnetic field or as fibres (see above). Summary We have described an improved synthetic method for closely coupled laterally attached side-chain liquid crystalline poly- mers. Problems with the previously published method of Zhou arise because of the unusually strong reducing power of NaBH, in non-aqueous media. The homopolymer of III exhibits a reversible liquid crystal phase confirming the work of Zho~,~,'~ although there is some confusion over the published NMR data.Copolymerization of I11 with methyl acrylate leads to a liquid crystal behaviour for copolymers containing up to 71 mol% methyl acrylate. This unusually high proportion of non-mesogenic diluent can be attributed both to the relative difference in bulk of the two monomers and the unusually broad temperature range over which a nematic phase is observed. Elastomeric materials can be prepared from these side-chain polymer systems, but there are some notable differ- ences in the behaviour seen from these materials and that observed from less closely bound systems. In particular, the levels of orientation achieved on application of a stress field are unusually low. It is clear that the behaviour of elastomers prepared from this system is severely perturbed by dynamic constraints arising from the extreme proximity of the bulky mesogenic unit and the polymer backbone.Experimental Charac terisa tion The composition of the copolymers was calculated from the integration of the relevant peaks in the 'H NMR; these were the peak at 6 =5.2 due to benzyl group derived from monomer I11 and the signal at 6=3.6 assigned to the methyl group in the methyl acrylate component. Molecular weight data were obtained by GPC, using dichloromethane as an eluent except in the case of LlOO for which chloroform was employed. The molecular weight data were obtained using a refractive index detector in conjunction with polystyrene standards; the data are included in Table 1, and are ‘corrected’ to compensate for the difference in molecu- lar weight of the monomer repeat units.The phase behaviour of the polymers was analysed using a Perkin Elmer DSC-2 calorimeter with approximately 10 mg samples and a scanning rate of 10°C min-’. A polarizing microscope equipped with a variable temperature unit was used to confirm both the nature of the liquid crystalline phases and the liquid crystalline to isotropic phase transition temperatures. Mechanical measurements were performed using a Rosand Precision Ltd. ‘Microscope’ tensile tested fitted with a 2 N transducer and a small oven to allow variable temperature measurements; the system has been described elsewhere.’, X-Ray scattering measurements utilized a Philips generator operating at 40 kV in conjunction with a pin-hole collimator and an incident beam monochromator to select the character- istic Cu-Ka radiation (A= 1.542 A). For measurements on the copolymer system, samples were analysed on a computer controlled 3-circle diffractometer operating in transmission mode.The X-rayo scattering intensity was measured over the range s =0.2-6.2 A-’ in steps of 0.02 A-’ where Is1=4.n sin @/A. For samples with a preferential orientation direction, the azimuthal variation in the scattering intensity was measured from a=0-360 in 9” steps at constant s where cl is the angle between the scattering vector Is1 and the symmetry axis of the sample. The data obtained was then converted to an orien- tation parameter (P,) given by eqn.(1). l I(a)sin a(3 cos’ a-1)/2da (1)(P,) = -2 I(a)sin clda The orientation parameter (P, ) relates to the average contri- bution of the mesogen, taking into account both the order parameter and the director distribution. In situ X-ray scattering on mechanically deformed samples utilized the AXIS system, in which the scattering pattern is collected on an area detector and the image can be stored on video, with the data analysis being provided by a computer system. Full details of this apparatus are described el~ewhere.~’ Ma terialsl 2,5-Bis( 4-methoxybenzoyloxy) benzaldehyde I. Compound I was prepared using the method of Zhou et The crude product, obtained from 2,5-dihydroxybenzaldehyde ( 14 g, 100 mmol), was dried under vacuum then recrystallised from toluene to give a compound which both TLC and NMR showed to be free of impurities (yield 70%); mp 189°C (nematic), 213 “C (isotropic); m/z 406 (M+)(HRMS: Calc., 406.1052; measured, 406.1059); vmax/cm-l 1722, 1690, 1604 and 1577; ‘H NMR [400 MHz, (CD,),SO] 6,: 3.8 [6H (OMe), 1We have adopted a simple numbering system to describe the aromatic protons in the range of structurally similar materials described in this account.This is as indicated below: H5 H4 H4, H’ Me0 Do OMe s], 7.16(7) [2H (H5,6 or H5’v6’), d fine splitting, Jortho8.81, 7.17(2) [2H (H576 or H5’,6’), d fine splitting, Jortho8.81, 7.57 [lH(H2), d, Jortho 8.81, 7.74 [1H (H3) dd, Jtneta 2-93 Jortho 8.81, 7.87 [lH (HI), d, Jmeta2.91, 8.14(4) [2H (H4*.’ or H4’v7’), d fine splitting, Jorrho8.81, 8.15(7) [2H (H4q7 or H4’,7’), d fine splitting, Jortho 8.81, 10.10 [1H (CHO), S].2-Methyl-4-( 4-methoxybenzoyloxy) phenol. 2,5-Bis(4-methoxybenzoyloxy) benzaldehyde (2.4 g, 6.0 mmol) was dis- solved in dimethyl sulfoxide (DMSO) (120 ml). To this solu- tion, NaBH, (1.2 g, 32 mmol) was added slowly at 10 “C. After addition of the NaBH, the reaction mixture was cooled to 0 “C and stirred for 4 h. Following this, the solution was poured into water (800 ml) with stirring to precipitate the product. This was then filtered, washed with water, dried under vacuum, then recrystallised from toluene to give a single product by TLC and NMR spectroscopy (yield ca.40%); mp 158-160 “C; m/z 258 (M+)(HRMS: Calc. 258.08921; measured, 258.0896) v,,,/cm-’: 3457, 1714, 1611, 1585 and 1512; ‘H NMR (250 MHz, CDCl,-CD,OD) 6,: 2.25 [3H (CH,), s], 3.9 [3H (OMe), s], 6.78 [lH (H’), d, Jortho 8.01, 6.85 [lH (H3), dd, Jmeta 2.0, Jortho 8.01, 6.94 [IH (HI), d, Jmetn 2.01, 7.00 [2H (H5*6),d, Jortho 8.51, 8.15 [2H (H4,7), d, Jortho 8.5); I3C NMR (63 MHz) 6,: 15.83 (CH,), 55.34 (OMe), 113.71(C576), 114.89, 119.27, 121.89, 123.50, 125.58, 132.04 (C”.’), 143.34, 152.50, 163.76, 165.79. 2-Methyl-4-(4-methoxybenzoyloxy)phenyl acrylate. 2-Methyl-4-(4-methoxybenzoyloxy)phenol was reacted with acryloyl chloride in THF containing triethylamine according to established pr~cedure.~’ The crude product was filtered, dried and then recrystallised from ethanol to yield a single compound by TLC and NMR (yield cu.60%); mp 109 “C; m/z 312 (M+)(HRMS: Calc. 312.0997, measured, 312.1007) vmaX/cm-’ 1725 and 1654; ‘H NMR (250MHz,CDCl3) 6,: 2.21 [3H (Me), s] 3.90 [3H (OMe), s], 6.03 [lH (HCH=), dd, Jgem 1.3, J,,, 10.41, 6.35 [1H (HCCO,), dd, J,,, 10.4,J,,,,,, 17.31, 6.64 [lH (HCH=), dd, Jgem 1.3, Jtrans 17.31, 6.98 [2H (H”‘), d fine splitting, J 9.01, 7.14-7.04 [3H m], 8.14 [2H (H4v7), d fine splitting, J 9.01; 13C NMR (63 MHz) 6, : 16.29 (CH,), 55.48 (OCH,), 113.82 (C5,6), 119.99, 121.76, 122.59, 124.09, 127.63, 131.49, 132.23 (C”.’), 132.57 (=CH,), 146.54, 148.48, 163.89, 164.10, 164.76. 2,5-Bis( 4-methoxybenzoyloxy) benzyl alcohol. 2,5-Bis(4-methoxybenzoyloxy) benzaldehyde ( 10.9 g, 27 mmol) was dis- solved in THF (1.2 1).To this solution, BH, *THF complex (100 mmol) was added slowly under a nitrogen atmosphere, ensuring the temperature remained below 0°C. After 2 h the reaction was quenched by the slow addition of air and water, until effervescence ceased. The solvent was then evaporated in uucuo and the remaining precipitate was filtered, washed with water then dried under vacuum and recrystallised from toluene to yield a single compound by TLC and NMR (yield >90%); mp 154-156°C; m/z 408 (M’); vmax/cm-l 1726; ‘H NMR (250 MHz, CDCl,-CD,OD) 6,: 3.91 [6H (OMe), s], 4.63 [2H (CH,), s], 7.00(0) [2H (H5,6 or H5’*6’), d fine splitting, Jortho 8.81, 7.00(6) [2H (H5q6 or H5’3@ ), d fine splitting, Jortho9.21, 7-17 [lH (H3), dd, Jmeta 2.6, Jortho 8-81? 7-21 [1H (H’), d, Jortho 8.81, 7.43 [lH (HI), d, J,,,, 2.61, 8.14(7) [2H (H43.’ or H4’.’’), d fine splitting, Jortho 8.81, 8.15(3) [2H (H4,7 or H4’7’), d fine splitting, Jortho9.21; 13C NMR (63 MHz) 6,: 55.31 (OCH,), 58.85 (ArCH,), 113.72 (C5,6 or C5’y6’),113.81 (C536 or C5’*6’ 1,120.80, 121.16, 121.33, 122.92, 132.13, 132.19, 145.27, 148.54, 163.92, 164.03, 164.00, 165.24 (Found: C, 67.58; H, 4.97; 0, 27.45. C,,H2@7 requires C, 67.64; H, 4.94; 0,27.42%).H6 H7 2,5-Bis( 4-methoxybenzoyloxy) benzyl acrylate 111. 2,5-Bis( 4- Hi kHO methoxybenzoyloxy) benzyl alcohol was reacted with acryloyl This numbering system is also applied to the I3C NMR spectra. chloride in THF containing triethylamine and a small amount J.Muter. Chem., 1996, 6(9), 1479-1485 1483 of 3,5-di-tert-butyl-4-hydroxytoluene(to inhibit polymens-ation) using a literature procedure 32 Purification of the crude material was carried out using column chromatography on neutral alumina with dichloromethane as the eluent and gave a single product by TLC and NMR (yield 60%), mp 119 "C, m/z 462 (M+)(HRMS Calc, 462 1314, measured, 462 1314), vmax/cm-l 1727, 1632, 1584 and 1516, 'H NMR (250MHz, CDC13) 6H 3 9 [6H (OMe), s], 5 2 [2H (CH20), s], 5 30 [lH (ITCH=), dd, Jgem 1 5, Jc,, 1151, 6 06 [1H (HCC02), dd, Jtra,, 17 5, Jc,, 11 51, 6 48 [lH (HCH=), dd, Jfrans17 5, Jgem 151, 7 OO(0) [4H (H5 ""), d fine splitting, Jortho7 6 (2 unresolved signals)], 727 [lH (H3), dd, Jmefa25, Jortho8 01, 730 [lH (H2), dd, Jpara 0 5, Jortho 8 019 7 38 C1H (H') dd, Jpara 0 5, Jmeta 251, 8 13(6) [2H (H47 or H4'7'), d fine splitting, Jorfho7 61, 8 14(5) [2H (H4 or H4'7'), d fine splitting, Jortho7 61, 13C NMR (63 MHz) 6, 55 50 (OCH3),61 35 (ArCH,), 113 87 (C5 or C5 "), 113 93 (C5 or C5' "), 121 26, 121 58, 122 64, 122 93, 123 67, 127 91, 129 43, 131 69 (=CH,), 132 32 (C4 4' "), 146 54, 148 47, 163 99, 164 09, 164 37, 164 62, 165 58§ Polymerisation.All polymensations were carned out in glass polymerisation tubes containing the comonomer and monomer I11 in the appropriate proportions as a 10% w/v solution in either THF or chlorobenzene AIBN (typically 4 mol%) was added to initiate polymerisation Polymensation was carned out in uucuo at 55 "C for 24 h The reaction mixture was then precipitated into cold methanol The polymer was then filtered, dissolved in dichloromethane and reprecipitated twice The punfied polymer was then dried overnight in a vacuum oven In all cases the absence of any detectable amount of solvent or unreacted monomer was confirmed by 'H NMR The spectroscopic data for two selected samples are included below Polymer sample L50 vmax/crn-l 3079,2954, 1731, 1605, 1581 and 1513, 'H NMR (250MHz, CDCI,) 6, 24-1 1 [(CHXCH,), broad], 3 6-3 2 [(OMe), s], 4 0-3 6 [(ArOMe), s], 5 2-4 7 [(CH,O), s], 8 1-6 9 [(Ar-H), broad], l3 C NMR (63 MHz) 6c 31 4, 34 9 (broad), 41 3, 51 5, 55 4, 61 0, 113 8, 1140, 121 2, 121 6, 122 8, 123 3, 129 4, 132 3, 148 4, 164 1, 173 (weak), 174 (weak) Polymer sample ,5100 vmaX/cm-' 1730, 1605, 1581 and 1512, 'H NMR (250 MHz, CDC13) dH 2 4-1 1 [3H (CHXCH,)O, broad], 5 2-4 7 [2H (CH,O), s), 3 9-3 5 [6H (ArOMe), s], 8 2-6 9 [11H (Ar-H), broad m], 13CNMR (63 MHz) 6, 29 64, 31 12,4043,41 19, 55 40, 60 87, 113 80, 113 92, 121 09, 121 54, 12242, 123 33, 129 33, 129 63, 132 21, 146 14, 148 39, 163 88, 164 13, 17203, 173 78 ~~~~ ~ ~ ~ Q Interpretation of the I3C NMR spectrum for this compound (and its precursor) was somewhat complicated by the perturbation to the symmetry imposed by the presence of the polymerisable unit on the central aromatic nng The predicted 13C chemical shifts on the basis of the data tabulated in Williams and Flemm~ng~~ are shown below Naturally this simple procedure is not sufficiently precise to predict any differences in the chemical shifts for the carbons of the 4-methoxybenzoyl substituents, however, by knowing the approximate position of the peaks It was possible to determine where the chemical shifts were too similar to allow resolution of the signals and where overlap occurred 49 166 8(b) 165 5 1220 /' 71 1 1484 J Muter Chem, 1996,6(9), 1479-1485 Cross-linked samples of the copolymer of 111 and hydroxy ethyl acrylate were prepared by casting films of the polyme from a dichloromethane solution containing the polymer an( the appropriate proportion of diisocyanatohexane and triethyl amine (added to catalyse the reaction between the isocyanatl units and pendant hydroxy functionality on the polymer) Thl solution was then heated at the required temperature fo several days l5 3-(4-Methoxybenzoyloxy) benzaldehyde.The ester was pre pared by the reaction of 3-hydroxybenzaldehyde with p-anisoy chloride in THF (50 ml) containing triethylamine as describe( above The product was dried under vacuum before finall: being purified by column chromatography (alumina witl dichloromethane as the eluent) to yield a single product b TLC and NMR (yield ca 40%), vmax/cm-l 1721, 1694, 1601 and 1577, 'H NMR [400MHz, (C03)2SO], 6, 699 [2€ (H56), d fine splitting, J 9 31, 7 49 [1H (H3),ddd, Jortho6 3 Jmetnunresolved], 7 59 [1H (H2),t, Jortho7 81 7 74 [lH (Hi] t, J,,,, 15 (2 equivalent)], 7 79 [1H (H ortho to CHO, part to 0-CO), dm, Jortho6 3, Jmeta 1, unresolved], 8 16 [2H (H4 '1 d fine splitting, Jorfho9 31, 1004 [lH (CHO), s], 13C NMF (100 MHz) 6,55 5 (OMe), 113 90 (C5 6), 121 25,122 62,127 18 128 01, 130 12, 132 43 (C47), 137 76, 151 67, 164 15, 164 53 191 23 (CHO) Reduction of 3-(4-methoxybenzoyloxy) benzaldehyde.344 Methoxybenzoy1oxy)benzaldehyde (0 05 g, 0 287 mmol) wa placed in a round bottom flask, a septum was fitted an( (CD,),SO (2 5 ml) was added A solution of NaBH, (0057 g 152 mmol) in D20 (001 ml) was added via a syringe (over period of a few minutes) to the round bottom flask and the reaction was then left at room temperature The reaction wa followed by 'H NMR (60 MHz), after reaction was complete a small amount of D20 was added and the reaction lef overnight High resolution NMR spectroscopy in conjunctior with GC-MS was then used to ascertain the product(s) formed which were not isolated, GC-MS major peak at m/z 15: (M+), 'H NMR [250 MHz, (CD3),SO] 6H 3 7 [3H (OMe) s], 4 31 [2H (CH,O), s], 4 40 [1H (OH), s], 6 45 [2H (H3 an( H ortho to CH, and para to 0-CO), d, Jortho7 8 (overlappinl signals)], 654 [lH (H'), broad], 685 [2H (H56), d finc splitting, Jortho 8 71, 6 94 [lH (H2), t, Jorfho7 71, 7 20 [2E (H47), d fine splitting, Jorfho8 51 2-(4-Methoxybenzoyloxy) benzaldehyde.The procedure use( for 3-Hydroxybenzaldehyde (see above) was repeated for the 2-isomer The product was dried under vacuum before finall! being purified by column chromatography (alumina witl dichloromethane as the eluent) to give a single product b! TLC and NMR (yield ca 30%) mp 82-84 "C, vmaX/cm-' 1725 1694, 1604 and 1577, 'H NMR (400 MHz, CDC13) 6, 3 9( [3H (OMe), s], 7 01 [2H (H5 6), d fine structure, J 8 81, 7 3: [1H (H,), dd, Jortho8 3, Jmeta101, 7 41 [1H (H meta to CHO para to ester), t, Jortho 7 61 7 67 [1H (H3), td, Jortho7 8, Jmet 14), 7 95 [lH (H'), dd, Jortho7 8, Jmeta 191, 8 18 [2H (H47) d fine splitting, Jortho 8 81, 10 22 [lH (CHO) s], 13C NMF (100MHz) 6, 55 5 (OMe), 11435 (C5,6), 12085, 12366 12633, 12840, 12982, 13253 (C"), 13573, 15265, 16431 164 64, 188 51 (CHO) Reduction of 244-methoxybenzoyloxy) benzaldehyde.The procedure used for the reduction of 3-( 4-methoxy benzoyloxy) benzaldehyde was repeated for 2-(4 +methoxybenzoyloxy) benzaldehyde, GC-MS m/z 109 (M ) 'H NMR [250 MHz, (CD,)SO] aH (from 2-methylphenol 202 [3H (CH,), s], 664 [lH (H para to OH), t, Jorfho731 6 80 C1H (H2), d, Jortho 7 31, 6 95 C1H (H3) td, Jorrho 7 3, Jmet 1 7],7 03 [1H (H'), d, Jortho7 31, (from 4-methoxybenzoic acid 3.77 [3H (CH3), s], 6.84 [2H (H596), d, Jortho8.81, 7.81 [2H (H4,’), d, Jortho 8.81.17 18 A. Hirai, G. R. Mitchell and F. J. Davis, New Polym. Muter., 1990, 1,251. K. H. A1 Ammar and G. R. Mitchell, Polymer, 1992,33, 11. This work was supported by the Science and Engineering Research Council through GR/F55126 and a studentship to E. A. W. We thank the EPSRC mass spectroscopy service at Swansea and RAPRA for molecular weight measurements for 19 F.J. Davis, J. Muter. Chem., 1993, 3, 551; P. Blaydon, E. M. Terentjev and M. Warner, Phys. Rev. El 1993, 47, 3838; W. Kaufold, H. Finkelmann, Makromol. Chem., 1991, 192, 2555; C. H. Legge, F. J. Davis and G. R. Mitchell, J. Phys. II, 1991, 1, 1253; J. Kupfer and H. Finkelmann, Makromol. Chem. Rapid Commun., 1991 12, 717; N. R. Barnes, F. J. Davis and G. R. monomer and polymer systems respectively. Mitchell, Mol. Cryst. Liq. Cryst., 1989, 168, 13; R. Zentel and M. Benalia, Makromol. Chem., 1987,188,665. References 20 H. C. Brown and S. Krishnamurthy, Tetrahedron, 1979, 35, 572; J. A. Meschino and C. H. Bond, J. Org. Chem., 1963, 28, 3129; E. Santaniello, P. Ferraboschi and P. Sozzani, J. Org. Chem., 1981, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 N.A. Plate, Ya.S. Friedzon and V. P. Shibaev, Pure Appl. Chem., 1985,57,1715. H. Finkelmann, in Polymer Liquid Crystals, ed. A. Ciferri, W. R. Krigbaum and R. B. Meyer, Academic Press, New York, 1982. G. R. Mitchell, M. Coulter, F. J. Davis and W. Guo, J. Phys. II, 1992,2, 1121. W. Kreuder and H. Ringsdorf, Macromol Chem. Rapid Commun., 1983,4, 807. F. Hessel and H. Finkelmann, Polym. Bull., 1985,14, 375. F. Hessel, R. P. Herr and H. Finkelmann, Macromol. Chem., 1987, 188,1597. F. Hessel and H. Finkelmann, Polym. Bull., 1986, 15, 349. M. S. K. Lee, G. W. Gray, D. Lacey and K. J. Toyne, Macromol. Chem. Rapid Commun., 1989,10,325. Q. F. Zhou, H. M. Li and X. D. Feng, Macromolecules, 1987, 20,233. Q. F. Zhou, H. M. Li and X. D. Feng, Mol. Cryst. Liq. Cryst., 1988, 155 B, 73.Q. F. Zhou, X. H. Wan, X. L. Zhu, F. Zhang and X. D. Feng, Mol. Cryst. Liq. Cryst., 1993,231, 107. G. Xu, W. Wu, D. Shen, J. Hou, S. Zhang, M. Xu and Q. F. Zhou, Polymer, 1993,34, 1818. G .R. Mitchell, F. J. Davis and A. S. Ashman, Polymer, 1987, 28, 639. W. Guo, F. J. Davis and G. R. Mitchell, Polym. Commun., 1991, 21 22 23 24 25 26 27 28 29 30 31 32 46,4584. H. B. Zhou, R. Xie, C. Deng, X. D. Feng and Q. F. Zhou, Acta Chim. Sin. Engl. Ed., 1992, 50, 1182 (abstract obtained from BIDS survey). P. Munk, Introduction to Polymer Science, Wiley, New York, 1989 G. R. Mitchell, in Comprehensive Polymer Science, ed. C. Booth and C. Price, vol 1, ch. 31, Pergamon, Oxford, 1989. W. H. Richtering, J. Schatzle, J. Adams and W. Burchard, Colloid Polym. Sci., 1989,267, 568. P. G. de Gennes, C. R. Acad. Sci. B, 1975,281, 101; Mol. Cryst. Liq. Cryst., 1973 12, 193. M. Warner, in Side-Chain Liquid Crystal Polymers, ed. C. B. McArdle, Blackie, New York, 1989. A. J. Symons, F. J. Davis and G. R. Mitchell, Proceedings of the 14th International Liquid Crystal Conference, Pisa, 1992; Liq. Cryst., 1993, 14, 853. A. J. Symons, Ph.D. Thesis, University of Reading, 1993; A. J. Symons, F. J. Davis and G. R. Mitchell, unpublished results. J. Schatzle, W. Kaufhold and H. Finkelmann, Makromol. Chem., 1989,190,3269; 1991,192,1235 F. J. Davis, W. Guo and G. R. Mitchell, Phys. Rev. Lett., 1993, 71,2947. P. Keates and G. R. Mitchell, University of Reading Technical Report, 1991. I. M. Vogel, Textbook of Practical Organic Chemistry, 5th ed., revised B. S. Furniss, A. J. Hannaford, P. W. G. Smith and A. R. 15 32, 1347. G. R. Mitchell, F. J. Davis, W. Guo and R. Cywinski, Polymer, 1991,32,1347. 33 Tatchell, Longman, UK, 1989. D. H. Williams and I Fleming, Spectroscopic Methods in Organic Chemistry, 4th edn., McGraw-Hill, London, 1987. 16 F. J. Davis and G. R. Mitchell, Annual meeting of the British Liquid Crystal Society, Sheffield, 1989,Polymer, 1996,37, 1345. Paper 6/03295H; Received 10th MUJ~,1996 J. Muter. Chem., 1996, 6(9), 1479-1485 1485

ISSN:0959-9428    

DOI:10.1039/JM9960601479

出版商:RSC    

年代:1996

数据来源: RSC