摘要:

AbstractWith the aim to determine the main structural characteristics of amorphous (branched and different‐unit) polymers of the polyphenylene type, prepared by polycyclocondensation of carborane‐containing mono‐ and diacetylaromatic compounds, an X‐ray structural study of four model compounds was carried out, viz. of 1,2‐bis[4‐(4‐acetylphenoxy)phenyl]‐1,2‐dicarba‐closo‐dodecaborane(12) (1) (triclinic crystals,a= 8,205 Å,b= 13,505 Å,c= 14,019 Å, α = 90,44°, β = 97,08°, γ = 97,24°, space groupP1,Z= 2,R= 0,045 for 2663 reflections), 1,2‐bis(4‐phenoxyphenyl)‐1,2‐dicarba‐closo‐dodecaborane(12) (2) (monoclinic crystals,a= 14,813 Å,b= 17,133 Å,c= 11,211 Å, β = 112,43°, space groupP21/c,Z= 4,R= 0,066 for 3 286 reflections), 1,2‐bis(4′‐acetylbiphenyl‐4‐yl)‐1,2‐dicarba‐closo‐dodecaborane(12) (3) (orthorhombic crystals, at −120°Ca= 13,405 Å,b= 9,276 Å,c= 22,86 Å, space groupPnam,Z= 4 molecules on themplane,R= 0,039 for 1 147 reflections), and 1,2‐bis(4‐acetylbenzyl)‐1,2‐dicarba‐closo‐dodecaborane(12) (4) (orthorhombic crystals, at −120°Ca= 22,03 Å,b= 26,23 Å,c= 8,026 Å, space groupFdd2,Z= 8 molecules lie on the two‐fold axis,R= 0,051 for 577 reflections). The strained structure of theC,C′‐o‐diphenyl‐substituted carboranyl fragment is established, the high conformational flexibility of 4‐phenoxyphenyl linkages is confirmed and a tendency toward separate autoassociation of acetyl‐containing polar groups and carborane nuclei is shown, with the autoassociation of polar groups completely suppressing that of carborane nuclei in case of conformational rigidity and shortness of the arylene linkages. These and other structural characteristics of the investigated model compounds and their crystals, in case they turn out to be characteristic also for the corresponding polymers and their precursors,

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890301

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThermal and photoinitiated copolymerizations of lipamide (1), a cyclic disulfide, with styrene in the absence of initiators were investigated. The thermal copolymerization is initiated via styrene radicals producing a copolymer with sulfide and disulfide linkages in the main chain and with amide and phenyl side groups. In the photopolymerization, the diradical formed by ringopening of1through homolytic fission of its strained disulfide bond is the main initiating species, attacking styrene to produce a copolymer with a high content of monomeric units of1.

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890302

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe polymerization of acrylamide initiated by 2,2′‐azobisisobutyronitrile in the system water/benzene and water/ethyl acetate (vol. ratio 3 : 1), the emulsion polymerizations of methyl methacrylate, butyl methacrylate, styrene and acrylonitrile, and the emulsion copolymerization of butyl methacrylate with acrylonitrile and styrene with acrylonitrile initiated by ammonium peroxodisulfate in the presence and/or absence of the inhibitor 4‐stearoyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl were studied. These systems represent a model of the partitioned polymerization. The partitioned polymerization is characterized by the deposition of a monomer and an initiator in different, mutually immiscible phases, e.g. water and oil phase, before polymerization. In order to start the polymerization the monomer (initiator) must transfer into the phase where the initiator (monomer) is situated. Application of the principle of partitioned polymerization led to the formulation of a novel approach to the initiation mechanism of emulsion polymerization of polar and non‐polar monomers initiated by water soluble or oil sol

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890303

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe polymerization of cyclopentene in the presence of an unsaturated ester led to the synthesis of low‐molecular‐weight polypentenamer with a terminal functional group by ringopening metathesis polymerization using WCl6/AlEtCl2/EtOH as catalyst. Unlike most reactions of this nature the efficiency of the catalyst system is high because the ester used possesses an electron withdrawing group, the trichloromethyl group. The presence of this group ensures that the complex formed between the metal carbene complex and the ester group is reduced in stability and catalyst concentrations normally used for ring‐opening metathesis polymerizations can be used (mole ratio W : CP = 1 : 1000), the concentrations of ester being quite high (mole ratio ester : CP = 1 : 5). Under these conditions reasonably high yields of liquid polymers are obt

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890304

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractPhotochemical hydrogen peroxide catalyzed degradation of both natural rubber and syntheticcis‐polyisoprene is shown to result in the formation of a low‐molecular‐weight oil functionalised with hydroxyl, carbonyl and epoxide groups. Interestingly, the epoxide groups are shown to be of atrans‐configuration. A scheme is proposed to account for the formation oftrans‐epoxide as well as concomitant mainchain isomerization. The preferential formation oftrans‐epoxide in free radical oxidations strongly suggests that the naturally occurringcis‐epoxide, present in natural rubber, is due to a stereospecific enzymatic process, and is not the byproduct of radi

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890305

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe α‐chymotrypsin catalyzed peptide‐bond formation was demonstrated by coupling the monomerN‐methacryloylaminoundecanoylphenylalanine(3 c)with alanine‐tert‐butylester in a water/chloroform system yieldingN‐methacryloylaminoundecanoylphenylalanylalanyl‐tert‐butylester(7). The kinetics of the corresponding α‐chymotrypsin catalyzed coupling of alanine‐tert‐butylester with methacrylic polymers containing aminohexanoylphenylalanine and aminoundecanoylphenylalanine as spacergroups was correlated with the Huggins coefficient of the polymer by

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890306

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe reaction of 1,3‐benzenedithiol(1)with 1,4‐diethinyl‐benzene(2)at room temperature yields polymers with thio‐1,3‐phenylenethiovinylene‐1,4‐phenylenevinylene repeating units. The polymerization proceeds without addition of an initiator and without UV‐irridiation. Because of the resulting structure a radical mechanism is suggested. However, the molar mass/conversion relation shows similarities with a step‐growth polymerization. Because of this behaviour this reaction was successfully used for the preparation of telechelics in which molar mass and end groups are controlled simply by the unstoichiometric ra

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890307

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractSolid ternary MgCl2/aromatic ester (A. E.)/TiCl4catalysts are obtained by grinding MgCl2followed by co‐grinding MgCl2and A. E. and then by TiCl4impregnation. The productivity increases with grinding time up to a maximum value and the stereospecificity decreases continuously. A convenient choice of the A. E. improves the results. The productivity seems to be correlated with details of the pore size distribution. Infrared analysis of the catalyst reveals different ways of Ti‐fixation but without clear relation to the catalytic propert

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890308

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractVinyl alcohol (VA)/4‐vinylpyridine (4VP) graft copolymers were prepared by the macromonomer method. After domain fixing of the PVA matrix of this graft copolymer, the water/1‐propanol mixed solution of poly(sodiump‐styrenesulfonate) (PSSS)/P4VP polymer blends was cast on the microheterophase surface of VA/4VP graft copolymer which served as a support membrane. The surface characterization of this composite membrane was carried out by means of transmission electron microscopy (TEM) and Electron Spectroscopy for Chemical Analysis (ESCA). The TEM observation indicated that charge mosaic microdomains formed by means of epitaxial growth are oriented perpendicularly to the film surface. The ESCA results clearly indicated that the two‐phase composition of the surface (in sampling depths of ≈ 1 and ≈ 5 nm) is proportional to the overall bulk composition of the pol

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890309

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe glass‐transition temperature,Tg, of poly(vinyl chloride) (PVC) has been found to depend linearly on both the overall isotactic triad content and a small fraction of isotactic triads. It was previously demonstrated, that the latter react with sodium benzenethiolate at temperatures as low as −30°C, probably because they adopt a definite local conformation. In general, it was believed before that the tacticity effect onTgoccurs only for disubstituted CC‐polymers, the results obtained in this work for PVC would suggest that specific conformations of isotactic triads can also enhance the motion of chain segments in the

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890310

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY