摘要:

AbstractElectrolysis of solutions of isoprene in tetrahydrofuran‐initiated living‐anionic polymerization was studied. The concentration of living ends was measured by spectrophotometry and could be maintained at any desired level by adjustment of the charge passed through the solution. An electronic feedback device, which regulated current flow to maintain constant optical absorbance, permitted kinetic studies at constant concentration of living ends. Simple first‐order kinetics could be observed in these systems at constant living anion concentration, despite a rapid attrition of living ends due to interaction with the solvent. The number of living anions could be reduced quantitatively by reversal of the impressed current. The control of the anion concentration implied a companion control over the molecular weight distrib

ISSN:0449-2994    

DOI:10.1002/polc.5070230103

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

年代:1968

数据来源: WILEY

摘要:

AbstractDilute poly(vinyl chloride) solutions exhibit a number of anomalies, such as dependence of solution properties on polymerization conditions, strong aggregation in some solvents, low solubility of the fraction with the highest molecular weight, and considerable polydispersity of fractions with higher molecular weights. On the basis of the authors' work and the literature data a survey of these anomalies is given, followed by an attempt to explain them from a unitary viewpoint. Most of the phenomena mentioned can be ascribed to the enhanced crystallization capability of syndiotactic sequences in the chain.

ISSN:0449-2994    

DOI:10.1002/polc.5070230104

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

年代:1968

数据来源: WILEY

摘要:

AbstractPhotopolymerization of methyl methacrylate initiated by labile azo compounds absorbing in the range of visible light was studied. The activation energy of the decomposition of the initiators used is much lower than the energy corresponding to the light absorbed. The results were compared with diacetyl‐initiated polymerization and made possible the conclusion concerning the relation between the structure and the initiation capabilit

ISSN:0449-2994    

DOI:10.1002/polc.5070230105

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe structure of poly(methyl methacrylate) prepared by anionic polymerization was followed. Compounds of lithium, sodium, and potassium were used as initiators. The influence of the structure of the initiator and its amount and of the monomer concentration, conversion, and temperature on the structure of the polymer in the polymerization without the presence of complexing solvents was studied. By analysis of NMR spectra tacticity and stereoblock structure, characterized by the parameter η =pis/(pis+pss), was determined. The results made possible the conclusions concerning the factors controlling the growth reaction

ISSN:0449-2994    

DOI:10.1002/polc.5070230106

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

年代:1968

数据来源: WILEY

摘要:

AbstractTo elucidate the chemical factors influencing the structure of radical poly(vinyl chloride) the effect of chain transfer agents was studied. With decreasing degree of polymerizationPthe association capability of the polymer slowly decreases. From the region of aboutP= 250 down the aggregation abruptly increases independently of the chain transfer agent used. The influence of copolymerization with a small amount of vinyl acetate under the conditions given was followed. The stereoregularity of the products formed and the content of foreign groups were determined. The results were correlated with kinetic data. The conditions of formation of poly(vinyl chloride) with a regular structure and a strong ability to aggregate are discussed.

ISSN:0449-2994    

DOI:10.1002/polc.5070230107

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

年代:1968

数据来源: WILEY

摘要:

AbstractStereoregular and irregular long‐side‐chain poly(alkyl acrylates) and poly(vinyl esters) have been obtained. A study of the structure these polymers showed that their crystallization took place as hexagonal cells, regardless of the stereoregularity. Studies of the effect of polymer branching length on supermolecular structure have shown that the minimal length of side chain required for crystallization probably is 10 carbon atoms, regardless of the stereoregularity of the backbone cha

ISSN:0449-2994    

DOI:10.1002/polc.5070230108

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe pyromellitamic acid prepared from pyromellitic anhydride andp:p′‐diamino‐diphenyl ether (the precursor of the heat‐resistant polyimide) can be dissolved in aqueous organic bases to form solutions which, unlike those of the free acid dissolved in highly polar organic solvents, are resistant to hydrolytic degradation. These solutions on drying and heating evolve the base to yield the pyromellitimide polymer and can be employed in fabrication processes, particularly for the formation of films and surface coatings. Data are presented on the properties of the solutions and derive

ISSN:0449-2994    

DOI:10.1002/polc.5070230109

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

年代:1968

数据来源: WILEY

摘要:

AbstractFour kinds of aminophenylbenzimidazoles were synthesized by reacting 3,3′‐diaminobenzidine and 1,2,4,5‐tetraaminobenzene withp‐ andm‐aminobenzoic acid. These four diamines were polymerized with pyromellitic anhydride and 3,3′,4,4′‐benzophenone‐tetracarboxylic anhydride. Polymers of highest intrinsic viscosities were obtained by adding the powdered anhydrides to dimethylsulfoxide solutions of the amines. Permutation of the above monomers yielded eight different benzimidazole–aromatic imide copolymers which were cast from solutions and cured at 280°C. to 300°C. in air. The polymer films show excell

ISSN:0449-2994    

DOI:10.1002/polc.5070230110

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

年代:1968

数据来源: WILEY

摘要:

AbstractIn a search for a correlation of commercial gelatin test results (Bloom jelly strength and viscosity) with molecular properties, molecular weight distributions were estimated and related to intrinsic viscosities on separate gelatin solutions heated at 95°C. and pH 3.9 for graded periods of up to 48 hr. Number‐average molecular weights based on the estimated distributions were used for estimating the number of groups available for formol titration as a check on the procedure, while solution viscosities were compared with those calculated from the distributions. The need for further work and also the necessity of recognizing the essential polyelectrolyte character of much commercially tested gelatin is appare

ISSN:0449-2994    

DOI:10.1002/polc.5070230111

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

年代:1968

数据来源: WILEY

摘要:

AbstractPoly(methyl methacrylate) films of various thicknesses were degraded in stainless‐steel closed reaction vessels and in closed quartz vessels of different wall thicknesses over a range of temperatures from 350 to 500°C. Above certain temperatures monomer formation becomes diffusion‐controlled. The degree of this diffusion control depends on the type of reaction vessel, wall thickness of the vessel, and film thickness. The rates of monomer formation for a definite percentage of conversion depend on the thermal history of the polymer sample. Thus, for the same percentage of conversion and the same film temperature the rates can become quite diffe

ISSN:0449-2994    

DOI:10.1002/polc.5070230112

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

年代:1968

数据来源: WILEY