摘要:

AbstractPolymerization of methyl methacrylate admixed with natural rubber occurs on rupture of rubber molecules to free radicals by applied shearing forces. The polymeric products after different conditions and extents of reaction have been separated into uncombined rubber, two interpolymer fractions, and uncombined polymethyl methacrylate by fractional precipitation and extraction methods. The structure of the interpolymers has been investigated by measurement of composition and osmotic molecular weight, ozonolysis to degrade the rubber segments and isolation of the polymethyl methacrylate fragments, autoxidation of the rubber segments, and viscosity measurements on the uncombined rubber. The interpolymer is a linear block polymer containing one polymethyl methacrylate segment and of the order of one or two rubber segments per molecule. The Trommsdorff gel effect has a profound influence on the rate of formation, composition, and structure of the interpolymer.

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510801

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractCopolymers of vinyl bromide with methyl methacrylate and with styrene were preparedin vacuoeither thermally at 28°C. or by UV irradiation at 0°C., using 2,2′‐azobisisobutyronitrile as initiator at 28°C. and as photosensitizer at 0°C. The reactivity ratios of the two systems were determined in bulk for both modes of initiation. They were similar in all four cases. The stability of some of the copolymers was compared

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510802

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractIt has been found possible to control the time of growth of polymerizing styrene radicals by adding overwhelming amounts of free radicals at intervals to an emulsion polymerization system. The styrene chains initiated in one addition are mostly terminated in the next addition, so that their growth time is the interval between additions. Polymers with the molecular weights of most of the molecules very narrowly concentrated around selected values can be prepared in this way. Ultraviolet light plus azoisobutyramide has been found to be a practical initiation system for preparing polystyrenes in this way with molecular weights greater than 500,000. The upper limit of the molecular weight obtainable is determined by the rate of chain transfer. For styrene at 0°C. this upper limit appears to be a few millions

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510803

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractThe number‐average molecular weight of a corn amylopectin sample is concluded to be approximately 300,000 on basis of both osmotic pressure and reducing group determination. The weight‐average molecular weight of this preparation was previously shown to be approximately 80 × 106. The ratio ofMw/Mnis in accord with that expected on the basis of an essentially random synthesis of the branched polymer. Further evidence for an extreme heterogeneity in amylopectins in provided by light scattering studies on subfractions prepared by fractional centrifugation. Conclusive evidence for this broad heterogeneity is obtained by ultracentrifugal analysis. The distribution of sedimentation coefficients is shown to be extreme, significant percentages of the polymer having sedimentation constants ranging from almost zero to above 400 Svedberg units. Some observations on the sedimentation behavior of other amylopectins, their β amylase limit dextrins, and corn amylose are

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510804

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractBased on a continued fraction expansion of the logarithmic function, ladder‐type structures are constructed which exhibit, either approximately or over a limited range of frequencies, a loss behavior that is often encountered in high polymers not only in the dielectric behavior but also in rheology,viz., a loss per cycle that is independent of frequency down to extremely low frequencies. Although such formal models have in general no direct bearing on the actual mechanism, in the present case one of them seems to suggest a molecular model in which groups of molecules are crosslinked into spindleshaped aggregates and immersed in the viscous liquid constituted by the remaining molecule

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510805

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractBy the concurrent use of the ion exchange membrane electrode in addition to the sodium amalgam electrode, the ionic activity of sodium ion in salt‐free polyelectrolyte solutions was determined over a considerably wide range of sample concentration. As polyelectrolyte samples, several kinds of sodium polyvinyl alcohol sulfates differing in their degrees of esterification and degrees of polymerization (sodium polystyrene sulfonate, sodium cellulose sulfate, and carboxymethylcellulose) were used. The peculiar dependency of the activity coefficient of sodium ion upon the sample concentration first noted by Kern was confirmed with all samples in this study; that is, γNa+decreases with dilution of the sample solution. Further, it was confirmed that the degree of esterification,viz., the charge density on a linear polymer, is a most important factor while the activity coefficient is entirely independent of the degree of polymerization. The influence of structure of the polymer skeleton upon the activity coefficient was found to be comparatively small. Some of the above results were discussed on the basis of the authors' theory published in a previous pap

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510806

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractThe temperature‐dependence of specific volume, rigidity modulus, and mechanical losses of plasticized and unplasticized cellulose acetates in the temperature range −100 to +200°C. has been studied. Two cellulose acetates, a triacetate and a cellulose (2.2) acetate were used, these being plasticized with varying amounts of either benzyl acetate,m‐cresol,o‐ethylphenol, γ‐butyrolactone, monomethylaniline, benzylphenol, or Santophen 7 (a phthallyl glycolate). The specific volume measurements, made using an extremely sensitive dilatometer, indicated three apparent second‐order transitions and one first‐order (melting) transition in cellulose triacetate and three or possibly four apparent second‐order transitions but no first‐order transition in the cellulose (2.2) acetate. Both the first‐order and second‐order transitions were depressed by the addition of plasticizer, the depression being most marked with the phenolic‐type plasticizers. Because of polymer decomposition at temperatures above 200°C., it was not possible to study the melting of mixtures containing less than 30% plasticizer and subsequently no reliable values for the melting temperature, the entropy, and the heat of crystallization could be determined. Rigidity modulus measurements, obtained using a torsional pendulum technique and the mechanical loss (damping) measurements, confirmed the existences of these second‐order transitions in both acetates and indicated that only the highest temperature transition, 175°C. in the triacetate and 195°C. in the secondary acetate, had the characteristics of a nor

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510807

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractThe complex dielectric constant of a pure molecular weight fraction of polyethyl methacrylate was determined over a frequency range of 30 to 3 × 105cps. and a temperature range of −73 to 133°C. The d.c. volume resistivity–temperature behavior was also determined. The data indicate the presence of two transition regions. It is shown empirically that superposition in its present form cannot be applied to these

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510808

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractThe complex dielectric constant of a pure molecular weight fraction of poly‐n‐butyl methacrylate was determined over a frequency range of 30 to 3 × 105cps. and a temperature range of −74 to 114°C. The d.c. volume resistivity–temperature behavior was also determined. The data indicate the presence of two transition regions. Comparison of these data with those on polyethyl methacrylate shows that the transitions in the butyl polymer are further apart in temperature than in the ethyl polymer. Further, the data show that the ethyl chain is stiffer than the butyl chain. An attempt at superposition of the normalized complex dielectric constant was unsuccessful. Calculation of the distribution function of relaxation times for several temperatures shows a marked temperature dependence of this

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510809

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202510810

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY