摘要:

AbstractN‐substituted polycarbamates of relatively low molecular weight have been prepared from the condensation of 1,6‐hexanebischloroformate withN‐substituted diamines, both aliphatic and aromatic. The initial rates of thermal degradation of these polymers and of unsubstituted analogs have been determined at 230–285°C. by following the evolution of carbon dioxide. The results showed that the more thermally stable polymers were those derived from the substituted aliphatic diamines, having the formula [N(R)XN(R)COO(CH2)6OCO]nwhere X is (CH2)5or (CH2)6. When R was CH3and C6H5, the overallEAwas 31 and 46 kcal./mole, respectively. The polymers derived from aromatic diamines, where X was 4,′ 4‐C6H4CH2C6H4, showed low values forEA, approximately 15 kcal./mole, regardless of whether R was H or alkyl. This low thermal stability was shown to be caused by amine endgroups. Some evidence as to modes of thermal degradation was obtained from a

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020101

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractImproved methods for the synthesis ofp‐bis(dimethylhydroxysilyl)benzene are described. This useful monomer was prepared fromp‐bis(dimethylhydrogensilyl)‐benzene which was obtained in 60–70% yields fromp‐dibromobenzene and dimethyl chlorosilane by use of anin situGrignard technique. The great reluctance due to steric factors of thep‐silphenylene‐siloxane configuration to form cyclic structures has been amply demonstrated. The condensation polymerization ofp‐bis(dimethylhydroxysilyl)benzene in benzene solution has yielded high molecular weight, crystalline poly‐(tetramethyl‐p‐silphenylene‐siloxanes). The heat of fusion ΔHuof the tetramethyl‐p‐silphenylene‐siloxane was found to be 4350 cal./unit. The modified Staudinger equation relating intrinsic viscosity and weight‐average molecular weight was applicable over a range of 70,000–400,000. These results are summarized in the relationship, [η] = 1.12 × 10−4Mw0.75. Tetramethyl‐p‐silphenylene‐siloxanes were found to be more stable than dimethylsiloxanes both to atmospheric oxidation and degradation through volatile

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020102

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractHigh molecular weight block copolymers having the structure [(CH3)2SiO]a[(CH3)2‐Si‐p‐C6H4‐Si(CH3)2O](b)n, can be conveniently prepared from the copolymerization of hydroxy end‐blocked dimethylpolysiloxanes andp‐bis(dimethylhydroxysilyl)benzene by use of essentially nonequilibrating catalysts, such as tetramethylguanidine di‐2‐ethylhexoate orn‐hexylamine 2‐ethylhexoate. The values ofaandbabove may be altered by employing hydroxy‐ended dimethylpolysiloxane of different degrees of polymerization or by preforming tetramethyl‐p‐silphenylene‐siloxane units. If the length of a segment is maintained at a constant value in the copolymers decreasing the mole ratioa/bresults in higher tensile strengths and higher melting points which are manifestations of increased degrees of crystallinity. If the mole ratioa/bis held constant, increasing the length of the a and b segments leads to higher melting points and higher tensile strengths again reflecting an increase in the degree of crystallinity. High molecular weight copolymers [η] ranging from 1.0 to 2.1, possessing unstressed (unvulcanized) gum tensiles of 1000–2700 psi and elongations of 500–1000% can be readily o

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020103

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

Abstract1,5‐Diamino‐2,4‐ethylenehexamethyltrisilazane and related compounds were prepared by treating the corresponding chlorosilane intermediates with ammonia or an amine. When these monomers were heated in xylene solution at 140°C. in the presence of ammonium sulfate, linear silicon‐nitrogen polymers were obtained with molecular weights in the range of 7,500–15,000. Elemental analyses, infrared spectra, and the physical properties of the polymers support the proposed structure and polymeriza

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020104

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractPolymers of methyl, ethyl,n‐butyl,n‐octyl, andn‐cetyl acrylate were γ‐irradiatedin vacuo, and the effects of irradiation temperature (−196 to 56°C.) on energy yields for crosslinking and degradation estimated from gel fractions and swelling behavior of the gel. The extent of degradation is independent of polymer structure and reaction temperature, suggesting a molecular chain breaking process. Crosslinking, found to occur predominantly on the alkyl side chain, is independent of temperature above and below the polymer softening point, but is severalfold higher for irradiations above the softening point; these data seem to reflect the importance of segmental mobility of radiation produced polymer radicals in the crossl

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020105

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractFive desyl aryl sulfides were prepared for use as photoinitiators in the determination of the bulk polymerization rates of tetraethylene glycol dimethacrylate at 25°C. As a first approximation, the initial rates were first‐order with respect to monomer and one half‐order with respect to initiator. From this, approximate initial overall rate constants were determined. The data indicate that resonance stabilization of the dissociated radical seem to affect the polymerization rate. Complications arising from the auto catalytic gel effect were discu

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020106

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractCotton sliver, cotton linters, periodate‐chlorite‐oxidized cellulose, and several regenerated celluloses were photolyzed by 2537 A. ultraviolet light in a vacuum at 40°C. The changes in quantum yields of hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, aldehyde groups, carboxyl groups, and chain scissions with respect to quanta of light absorbed and initial functional group concentration indicated that photolysis of alcohol groups plays a dominant role in the complex of interdependent primary and secondary reactions taking place. Periodate‐chlorite‐oxidized cellulose is much more suceptible to photochemical degradation than is unoxidized cellulose. Neutralization with very dilute sodium hydroxide solution reduced the quantum yields of the oxycellulose to values similar to those obtained with the unoxidized

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020107

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractThe effects of the exchange of deuterium for hydrogen in the hydroxyl groups on the composition of products and the kinetics of their formation during the irradiation of cellulose by 2537 A. in a vacuum at 77, 313, and 365°K. are described. About 50–70% of the total hydrogen evolved was HD. Little D2was formed. Total HD evolution was independent of temperature. Disproportionation, rather than atom abstraction or atom combination, was likely to be the dominant mechanism of hydrogen production. Much of the aldehyde group formation takes place during the photolysis and probably results directly from secondary photolysis or disproportionation of radicals. H2, CO, and CO2evolutions increase with temperature and result from both functional group photolysis and radical depropagation. Chain scission and carboxyl group formation take place to a large extent during the post‐irradiative oxidation of long‐lived oxygencontaining ra

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020108

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractStyrene was copolymerized in bulk with cinnamonitrile, benzylidenemalononitrile, ethyl benzylidenecyanoacetate, and atroponitrile at 80°C. up to low conversions. The usual reaction scheme of copolymerization fitted only the pair styrene‐atroponitrile. The kinetic scheme of the other three pairs fitted the scheme proposed by Barb, taking into account the effect of the penultimate un

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020109

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractApplication of statistical mechanical theory gives the expressionr2= 27.9n− 20.3 relating the mean square end‐to‐end length,r2, of a random polypeptide chain in thetrans‐form andn, the number of amino acid residues in the chain. The corresponding expressions for thecisand nonplanar forms arer2= 8.6n− 0.8 andr2= 15.5n− 4.8 rrespectively. The first of these equations has been used to obtain an expression for the fractional decrease in length of a crosslinked, aligned α‐helical structure when it is converted to the random coil form. The assumptions made are that the crosslinkages undergo little lateral displacement and that the volume remains constant. The expression so obtained is\documentclass{article}\pagestyle{empty}\begin{document}$l/l_{0} = {{\left\{ {23.7n - 17.3 - [10\sqrt {l//l_0 } - 7]^2 } \right\}^{1/2} } \mathord{\left/ {\vphantom {{\left\{ {23.7n - 17.3 - [10\sqrt {l//l_0 } - 7]^2 } \right\}^{1/2} } {1.5n}}} \right. \kern-\nulldelimiterspace} {1.5n}} $\end{document}wherelis the supercontracted length of the polypeptide fiber,l0is its original length andnis the number of amino acid residues between

ISSN:0449-2951    

DOI:10.1002/pol.1964.100020110

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY