摘要:

AbstractInvestigations have been carried out in this laboratory over the past four years on the structure—property relationship in main chain, thermotropic liquid crystal polymers containing a variety of different types of mesogenic groups and flexible spacers. Our goal has been to relate the effect of polymer structure to the type of mesophase formed in the melt and to the melting and clearing temperatures of the mesophases. Many interesting, unusual, and unexpected results have been obtained in our survey, and this review is concerned with our observations on the molecular factors which determine the types of mesophases formed, nematic or smectic, and their transition temperatures and behavior

ISSN:0360-8905    

DOI:10.1002/polc.5070720103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractKinetic studies of reactions in systems containing polymers have led to the following observations: (1) In dilute solution the thermal and the photochemical isomerization of azobenzene residues is not impeded by their incorporation into a polymer backbone. In the glassy state, the kinetics of the isomerization of azobenzene residues in polymer side chains or backbones reflect the distribution of free volume and volume relaxation. (2) Reactions of polymers with low molecular weight reagents may be affected by neighboring group effects and by the contribution of the polymer backbone to the polarity of its microenvironment. (3) Attack of an enzyme on a polymer side chain depends sharply on the spacing of the susceptible bond from the chain backbone. (4) The expected “kinetic excluded volume effect” in reactions between two flexible chain molecules was not observed. (5) Reactions involving groups attached to a swollen crosslinked gel may reflect spatial variations of the local polarity. (6) Attack of water‐soluble reagents on latex particles may be restricted to the surface of the particle. (7) The presence of a polyion exerts various effects on reactions involving two small ionic sp

ISSN:0360-8905    

DOI:10.1002/polc.5070720104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractGiven good reactivity ratio data for free radical vinyl copolymerizations, the use of the Alfrey—PriceQ—escheme permits the assignment of reactivity parameter values for individual monomers and the prediction of unknown reactivity ratios. A new, statistically based method has been developed and tested on a set of 11 monomers to estimateQ–evalues for those monomers. The results of these estimates suggest that if care is exercised in the selection of monomer pairs for use inQ–edeterminations, theQ–escheme is quite reliable for reactivity ratio prediction on many mono

ISSN:0360-8905    

DOI:10.1002/polc.5070720105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThere are two principal types of low temperature polycondensation processes: the two‐phase process known as interfacial polycondensation and a single liquid phase process or solution polycondensation. Both procedures are widely used experimentally and have led to the preparation and evaluation of thousands of polymers. Types of polymers which are made commercially are polycarbonates, block elastomers, polyimides, and aromatic polyamides. Aromatic polyamides are produced commercially for two major end uses: (1) flame and heat resistant polymers in the form of fibers, films, molding powders, and papers, and (2) polymers with extended chains for high strength, high modulus fibers. The latter class of polymers give liquid crystalline solutions which make possible the direct formation of highly oriented, high strength fibers. Aramid fibers of this type are useful in cut resistant clothing, ballistics protection, asbestos replacement, ropes and cables, and reinforcement of resins and rubber. Continuing research on the low temperature procedures is leading to new variations and applications of these processe

ISSN:0360-8905    

DOI:10.1002/polc.5070720106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractA discussion of some current ideas on the molecular processes of rubber deformation is presented. Reference is made to some important experiments and to suggestions which have been proposed for their explanation.

ISSN:0360-8905    

DOI:10.1002/polc.5070720107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractExamples of functional monomers and latex polymers are described. Use of functional monomers allows great versatility in the design of latex polymers with specialized properties. Included are examples of electrophilic, nucleophilic, crosslinkable, hydrolyzable, and metalion‐chelating monomer

ISSN:0360-8905    

DOI:10.1002/polc.5070720108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractParaxylylene bisdialkyl sulfonium salts can be polymerized in several different ways, yielding addition polymers as well as condensation polymers. The chemistry leads to a variety of polymers including poly(p‐xylylene), poly(p‐xylylidene), poly(xylylene sulfide)s, poly(xylylene oxide)s, and various α‐substituted polyxylylenes such as poly(p‐xylylene‐α‐dialkylsulfonium chloride). Addition polymers form via xylylene diradical intermediates. Condensation polymerization can be effected either by coupling with aldehydes or by nucleophilic displacem

ISSN:0360-8905    

DOI:10.1002/polc.5070720109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractDr. Turner Alfrey was a scientific pioneer in the area of copolymerization. Copolymerization is a polymerization process in which more than the minimum number of monomers required to form a polymer are polymerized together to give a product which has incorporated in it the repeat units corresponding to all the monomers employed, and the products thus obtained are called copolymers. Copolymers can also be produced by employing the mutual reactions of functional polymers or oligomers or their reactions with the appropriate monomers. Both step‐growth and chain‐growth processes, the latter involving a free‐radical, ionic, coordination, or ring‐opening mechanism, can be used to make cop

ISSN:0360-8905    

DOI:10.1002/polc.5070720110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractSpontaneous addition and polymerization reactions between olefins of different electron densities result in a wide variety of small molecules and polymers. The small molecules include cyclobutanes, 1‐butenes, and pyrans; the polymers can be homopolymers and/or alternating copolymers. Tetramethylenes are proposed as key intermediates in most of these reactions. The tetramethylenes, generated by bond‐forming initiation, are hybrids of 1,4‐biradical and zwitterionic forms. The character is mostly determined by the substituents at the terminals. Zwitterionic character is favored by strong donors such as alkoxy and dialkylamino groups at the carbenium ion end, and strong acceptors such as two cyano groups at the carbanion end. Biradical character is favored by acceptor groups such as diester and cyanoester at the acceptor end, and aryl and vinyl as donor groups. Zwitterionic tetramethylenes initiate ionic homopolymerization, while biradical tetramethylenes initiate alternating copolymerization.This unifying concept ofbond‐forming initiationis extended to spontaneous addition and polymerization reactions of hetero‐atom acceptor molecules and 7,7,8,8‐tetrasubstituted quinodimethanes. Finally, compounds possessing labile σ‐bonds (mainly halogens and peroxides) fit the general scheme. In a few cases, coupling of tetramethylenes may contribute to polymer formation. Ion‐radical pairs, charge‐transfer complexes, and adventitious impurities are excluded as significant initiators.The bond‐forming initiation has been thoroughly discussed in a rece

ISSN:0360-8905    

DOI:10.1002/polc.5070720111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThe synthesis and characterization of isobutylene/styrene tri‐ and H‐block polymers, and the copolymerization of α,ω‐styryl polyisobutylenes with N‐vinyl pyrrolidone will be

ISSN:0360-8905    

DOI:10.1002/polc.5070720112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY