摘要:

AbstractModification of poly(N‐acylurethane)s (3a–c) by transesterification with hexyl alcohol and 2‐dodecyl‐1,3‐propanediol (2a) under mild conditions was studied.3were prepared by polyaddition of corresponding bis(N‐acylisocyanate)s and diols under mild conditions in good yields. Reaction of poly(N‐acylurethane) (3a) (Mn= 22700) with two equivalents of hexyl alcohol started around 100°C to give the corresponding degradation products (Mn= 7 300, 120°C, 90 min). A mixture of poly(N‐acylurethane) (3b,Mn= 17500) with an equimolar amount of2awas heated at 150°C under reduced pressure to remove 1,2‐propanediol. The polymer obtained was3aof which yield andMnwere 57% and 6900, respectively. Transesterification ofN‐acylurethane derived from phenol proceeded easier than that derived from alkanol. Aromatic poly(N‐acylurethane) (3c) derived from 4,4′‐dihydroxydiphenyl ether (2c) underwent a similar transesterification with2aat lower temperature (80°C) without removal of2cto give3ain 43% yield. Thus, the modification of poly(N‐acylurethane)s (3) could be readily achieved by the transesterification with mono alcohols and diols under mild

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970601

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe report the synthesis and characterization of a new ferroelectric liquid crystalline side chain copolymer containing photoisomerizable chromophores and non‐photoisomerizable mesogenic units. On illumination with UV‐light a suppression of the polar order is obtained as indicated by a substantial drop of the spontaneous polarization (PS) compared to the dark state. We interpret this as the phase order being disrupted by thecis‐isomer of the chromophore. After illumination with VIS‐light only the major part ofPsis restored. The photochemicalcis‐transback‐isomerization (restoration of the phase) leads to a different stationary state than the dark state of the material. The thermal reisomerization (cis‐trans) in the liquid‐crystalline phase was observed to be faster than in solution by one ord

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970602

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractOlefin polymerizations were conducted with novel multimetallic zirconocene catalyst systems: RCpCpZrCl2(1) (R = dimethylsilylferrocene; Cp = cyclopentadienyl) and (RCp)2ZrCl2(2) in combination with methylaluminoxane or tetrakis(pentafluorophenyl) borates. In ethylene polymerization, the maximum catalyst activity was observed at a lower temperature (30–45°C) when using complex1or2, compared with Cp2ZrCl2. It was also revealed that complex1is a more effective catalyst than Cp2ZrCl2for copolymerization of ethylene and p

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970603

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWater‐soluble polydepsipeptides with functionalized side‐chain groups, i.e., alternating copolymers, consisting of glycolic acid (Glc) andL‐lysine (L‐Lys),L‐aspartic acid (L‐Asp) orL‐glutamic acid (L‐Glu) residues as α‐hydroxy acid and α‐amino acid residues, respectively, were synthesized, and their biodegradation behavior was investigated. Three kinds of polydepsipeptides, poly(Glc‐alt‐Lys), poly(Glc‐alt‐Asp) and poly(Glc‐alt‐Glu), were synthesized by means of ring‐opening polymerization of the corresponding cyclodepsipeptides and subsequent deprotection of benzyl and benzyloxycarbonyl groups. In order to estimate the main‐chain cleavage behavior of polydepsipeptides with functionalized side‐chain groups, the hydrolysis behavior of the obtained water‐soluble polydepsipeptides was first investigated in phosphate buffer s

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970604

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe transfer constants of 1‐dodecanethiol and non‐ionic thiol‐ended surfactants (transurfs) have been determined for the bulk polymerization of styrene at 70°C; these values are 19 for l‐dodecanethiol and 19 and 14 for the transurfs with 17 and 90 ethylene oxide units, respectively. Transfer constants are obtained from the high‐molecular‐weight portion of the full number molecular weight

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970605

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPure 4,4′‐bis(2,3‐epoxypropoxy)biphenyl (1) has been synthesized and its mesophase behaviour has been investigated.1forms a monotropic nematic mesophase with a virtual clearing temperature of 109°C.1has been cured with 2,4‐diaminotoluene (3), 4,4′‐diaminobiphenyl (4), and 4‐aminophenyl 4‐aminobenzoate (5) to investigate the possibility of formation of anisotropic networks. Virtual clearing temperatures of the diamines indicate that liquid crystalline thermosets (LCT's) might be obtained with4and5. Crystallization of oligomeric products from the isotropic melt of1with3or4, respectively, occurred on isothermal curing without formation of a mesophase, while a nematic LCT wa

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970606

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractLiquid crystalline polyesters as host polymers and paramagnetic metal complexes as guest molecules were prepared, and melt‐drawn fibers were made from their blend at mesophase temperature. The wide‐angle X‐ray diffraction patterns of the fibers indicated that the nematic or smectic phase is frozen during melt‐drawing. The molecular orientation of the metal complexes in the fibers was investigated by means of ESR. The order parameter obtained from the ESR spectra of the fibers suggests that the base of the square planar Cu(II) and pyramidal V(IV)O complex is almost completely oriented parallel to the f

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970607

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractNew hydrolyzable gels bearing saccharide,L‐lysine, and poly(oxyethylene) moieties were prepared via polyaddition of methyl ß‐D‐glucofuranosidurono‐6,3‐lactone (1) and poly(ethylene glycol) PEG,Mn= 1000 with anL‐lysine derivative, methyl (S)‐2,6‐diisocyanatohexanoate (2), using dibutyltin dilaurate and triisocyanate3as a catalyst and a crosslinking agent, respectively. The swelling ratio and rate of hydrolysis of these gels in phosphate buffers increased with the content of PEG. Hydrolysis of these gels was enhanced by increasing the pH of phosphate buffer solution in the range from 5.5 to 8.0, while the gel having only repeating units derived from1and2but no PEG was hardly hydrolyzed in any buffer solutions (pH 5.5, 7.0, 8.0). The release of hydrophilic 5(6)‐carboxyfluorescein (CF) from these gels in buffer solution of pH 8.0 was faster than that of hydrophobic magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS). The release of ANS from the gel was enhanced with the swell

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970608

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA diol monomer bearing carbazole units substituted with one acceptor group was prepred starting from 3‐formyl‐9‐(4‐hydroxybutyl)carbazole and hexamethylene bis(cyanoacetate) via Knoevenagel condensation. Main‐chain polyurethanes with acceptor‐substituted carbazole as nonlinear optical chromophores were obtained by addition polymerization of the carbazole diol monomer with various diisocyanates in tetrahydrofuran at room temperature using dibutyltin diacetate as a catalyst. These carbazole main‐chain polyurethanes were found to have glass transition temperatures in the range of 113–122°C and weight‐average molecular weights in the range of 6300–11000 g/mol. The chloroformsoluble polyurethanes could be spin‐coated into thin films with good optical quality. After poling, these films displayed reasonable second harmonic generation efficiencies. Preliminary results indicated that the polyurethanes have good thermal stability compared to analogous polymers

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970609

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractUsing1H,6I i,7Li and13C NMR, di‐tert‐butyl 2‐lithio‐2,4,4‐trimethylglutarate (A) as a dimeric model of the living poly(tert‐butyl methacrylate) is shown to form well‐defined aggregates with lithiumtert‐butoxide (B) in tetrahydrofuran. The prevailing aggregates with the compositionA2B2andAB3are controlled mainly by the ratioA:B. The initial mixture of aggregates is formed very fast but is metastable. Using 1D and 2D spectra,1H‐1H and1H‐6Li nuclear Overhauser effect and relaxations of1H,7Li and13C, both aggregates are shown to exist mainly in three conformational forms (b, c, d) of theA‐part which are very similar in both aggregate types. In agreement with the previously published infrared spectra, formdhas the γ‐ester group ofAcoordinated to Li.ddoes not exchange with the ‘open’ formsborcwith perceptible rate on the NMR time scale. Its population is promoted by a larger content ofBin the aggregate. Bymodifiedneglect ofdifferentialoverlap (MNDO) quantum calculations, the aggregatesA2B2andAB3are predicted to have a roughly cubical core (OLi)4which is distorted in thedform where one (AB3) or two (A2B2) Li atoms are pulled out of the cube by coordination to the γ‐ester group. The stabilization of the supramoleculeA2B2orAB3and the promoting effect ofBon intramolecular coordination to the γ‐ester group inAis explained in terms of a cooperative system of polycentric

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970610

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY