摘要:

AbstractThe polymerization of styrene, initiated by lithium diethylamide in mixtures of benzene and THF, has been investigated. Kinetic and molecular weight measurements are interpreted on the basis of simultaneous initiation and propagation steps, and the effect of solvation and coordination processes on these reactions is discussed. Initiation of polymerization is thought to involve addition of solvated lithium diethylamide ion‐airs to styrene, giving species with diethylamide end groups. The possible influence of these end groups on the initiation is considered in terms of an intramolecular cyclization process. Propagation of polymerization is believed to involve polystyryllithium ion‐pairs, solvated to varying extents by THF. No evidence has been found to suggest that chain transfer, or termination, reactions are an integral part of the polymerization process. The polymerization has a number of similarities to the alkyllithium‐initiated polymerization of styrene, but also exhibits some interesting differ

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140701

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effect of stress transfer‐limited swelling in the surface region on the hydroxylation of styrene–butadiene–styrene block copolymers in the bulk state was investigated. Films of the copolymer were allowed to react with peracetic acid to effect epoxidation and simultaneously with acetic acid and water to cleave the epoxy rings. By infrared spectroscopy it was observed that the hydroxyl content of the films decreased with increasing film thickness and the epoxy content increased commensurately. This was attributed to the presence of a lag between the advancing diffusion fronts for the epoxide groups and for the cleavage agents. This lag increases with increasing thickness due to the presence of stress‐transfer mechanisms which act to reduce the degree of swelling in the surface region and which are more effective in thicker films. The hydroxyl content increased exponentially with time, giving rise to the observation of significant induction time before there was any infrared evidence of hydroxyl formation. This resulted from the relief of part of the compressive stress in the surface region by the reaction process, which in turn increased the permeation rate of

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140702

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractPolyisophthalamides and polyterephthalamides were prepared by the solution polycondensation of the corresponding diacyl chlorides with 4,4′‐diaminobibenzyl,trans‐4,4′‐diaminostilbene, and 4,4′‐diaminotolan inN,N‐dimethylacetamide (DMAc). Polypyromellitimides were synthesized in two steps by the ring‐opening polyaddition of pyromellitic dianhydride with the aromatic diamines in DMAc, followed by thermal cyclodehydration. The amorphous polyisophthalamides were soluble in some amide solvents containing lithium chloride, while the polyterephthalamides having fair degree of crystallinity were insoluble in these solvents. The thermal stability of these aromatic polymers decreased in the order of the tolan‐containing polymers>the stilbene‐containing polymers>the bibenzyl‐containing polymers, both in

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140703

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractBecause of the allylic nature of propylene, the vinyl chloride–propylene system exhibits polymerization behavior markedly different from that of vinyl chloride, even at relatively low propylene concentrations. Propylene acts as a degradative chain‐transfer agent, and as a result, both the polymerization rate and the molecular weight of the resultant copolymers are lower than those of the homopolymer, decreasing with increasing propylene content. Even at propylene concentrations as low as 10% the rate of polymerization is proportional to the initiation rate, indicating kinetic control by the propylene. The reactivity ratios of these monomers given by Cain were verified. The reciprocal intrinsic viscosity of the copolymer was found to be linearly related to the monomer feed composit

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140704

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractPhotolysis behavior of oxidized poly(vinyl alcohol) (PVA) in which carbonyl groups were introduced by oxidation with sodium hypochlorite and periodic acid was investigated by using ESR spectrometry. Increased formation of PVA radicals was observed in the sample with low degree of oxidation, which showed an emphasized formation of triplet component radical. On the other hand, the formation of radicals tended to be depressed in the highly oxidized sample, and a singlet component was dominant in the ESR spectrum. By examining infrared and ultraviolet spectra of the oxidized sample, the sample was found to contain two structures, a saturated ketone group and an α,β‐unsaturated group; the latter structure was intensified with increasing degree of oxidation. Based on ESR studies of the photoirradiated acetone and mesityl oxide, the models of saturated and α,β‐unsaturated ketone structures in the oxidized PVA, respectively a photodecomposition mechanism of oxidized PVA was p

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140705

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractDTA (differential thermal analysis) traces for various kinds of polystyrene and substituted polystyrenes, including bulk‐polymerized, monodisperse, and isotactic samples, have been recorded below the glass temperature. It has been shown that the β transition is dependent upon polymer structural modification, traces of water or solvent, and sample thermal history. The experimental data presented here support the conclusion that the β transition is due to conformational changes involving backbone motions and phenyl ring reorientat

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140706

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractOxidation of 1,4‐phenylenedimercaptan has given a cyclic trimeric disulfide. Oxidation of 1,3‐phenylenedimercaptan has yielded a similar product. These monomers have been incorporated in the chains of aromatic polyether, sulfone, ketone polymers and serve as crosslinking sites on heating these polym

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140707

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractAn anionic polymerization procedure for preparing multiblock copolymers of styrene and isoprene is described. The process is based on the initial specific incorporation of isoprene when mixtures of styrene and isoprene are polymerized with butyllithium in hydrocarbon solution. As examples, linear (AB)3block copolymers have been prepared by interrupting styrene polymerization by step additions of isoprene at times programmed according to the reactivity ratios and the rate constants for styrene and isoprene propagations. The products were characterized by means of osmometry, light scattering, gel‐permeation chromatography, and density‐gradient ultracentrifugation. The analyses showed that the multiblock copolymers are free from polymeric impurities and reasonably homogeneous in molecular weight and composition. The polystyrene segment lengths were analyzed by means of GPC after the oxidative degradation of the polyisoprene moieties in the copolymers. The results suggest that the polyisoprene blocks contain a nonnegligible amount of styrene but that this monomer is incorporated as very short segments. On the other hand the polystyrene blocks produced at the end of the copolymerizations appear to have narrow molecular weight distributi

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140708

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe anion of the isoquinoline Reissert compound, 2‐benzoyl‐1,2‐dihydroisoquinaldonitrile, reacts with polymeric aldehydes in essentially complete conversion, leading to polymeric esters containing isoquinoline moieties. These can be completely hydrolyzed to the corresponding alcohols. The reactivity of the Reissert anion toward polymeric halides and aldehydes is rationalized on the basis of its moderate har

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140709

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe core and valence levels of a series of poly(alkyl acrylates) have been studied by ESCA. From an analysis of the individual component peaks for the C1sand O1score levels and from comparison of relative area ratios it is shown that ESCA may be applied to the study of surface compositions. The evidence presented strongly suggests that on the ESCA depth‐profiling scale the technique statistically sample the repeat units with no evidence for preferential orientation of side chains at the surface. For some samples, ESCA provides evidence for a degree of surface oxidation and hydrocarbon contamination. The valence energy levels are shown to be characteristic of the polymer system. The measured absolute and relative binding energies of the core levels have been compared with model calculations using the charge‐potential model in the CNDO/2 SCF MO formal

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140710

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY