摘要:

AbstractMethods for rapid fractionation of polyvinyl acetate and of polyvinyl alcohol are described. By a slightly modified Fuchs' extraction technique, polyvinyl acetate can be fractionated into relatively homogeneous fractions. The ratio of osmotically determinedM̄nof the nonfractionated sample to that calculated from fractionation data is 1.19. Extraction fractionation of polyvinyl alcohol is complicated by the crystallinity of this polymer. The molecular weight distribution of polyvinyl alcohol can be determined, however, in relatively short time, by first reacetylating the polymer and then fractionating the obtained polyvinyl acetate

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512901

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractAutomatic recordings of the rates of sorption and desorption of gases are obtained by measurement of the volume of the ambient gas under conditions of constant pressure and temperature. The apparatus, which approaches microgram sensitivity, is applicable in the field of diffusion of vapors in polymeric solids (and in obtaining the permeability coefficient). It is especially suited for rapid detection of rate changes and provides operational conveniences for extended measurements. Although exhibiting an over‐sensitivity at low pressures, the apparatus does not share the load‐sensitivity limitations of quartz spiral techniques. As a detector of the kinetics of gas evolution or consumption, the apparatus shows promise of application in other fields of research as w

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512902

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractGraft copolymers, were synthesized from hydrophobic backbone copolymers by introducing hydrophilic grafts at appropriate juncture points. Poly(styrenecodimethyl maleate) of varying composition was prepared by the copolymerization of styrene with dimethyl maleate in the presence of benzoyl peroxide as the initiator. Data on conversion rates of initial monomers to copolymer, infrared measurements, limiting viscosity numbers, and copolymer compositions are presented. The poly(styrenecodimethyl maleate) was resistant to saponification but, when reacted with sodium catalyzed monoethanolamine at its boiling point, yielded the desired poly(styrenecomaleic ethanolamide). Addition of ethylene oxide to the available hydroxyl groups yielded, in some instances, water‐dispersible graft copolymers. Poly(styrenecoallyl acetate) was prepared by copolymerizing styrene with allyl acetate with use of benzoyl peroxide as the initiator. Water‐dispersible copolymers from this backbone copolymer were prepared by saponification of the acetate groups and the grafting of ethylene oxide to the available hydroxyl groups in the backbone copolymer. Results of analyses, molecular weight determination, and infrared measurements are presen

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512903

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride), polymerized with the use of γ‐radiation, benzoyl peroxide, and 2,2′‐azobis(isobutyroitrile) as initiators, was thermally decomposedin vacuo.The gaseous decomposition products as analyzed by mass spectrometry consist primarily of hydrogen chloride for decomposition temperatures below approximately 300°C. At temperatures approximating 400°C., various hYdrocarbons are evolved along with the hydrogen chloride. Energetic considerations are discussed and the activition energy is determined. A free radical mechanism for the dehydrochlorination reaction that appears consistent with the reaction rate data for a three‐halves‐order reaction i

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512904

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractChemical and physical changes produced in polymethacrylates and polyacrylates by ionizing radiations are examined in the light of data revealing molecular structural changes and ultimate fragmentation products. A 1,4‐diradical or concerted mechanism is postulated for polymethacrylate main‐chain sciss

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512905

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractReaction conditions for improving the yield of the crystalline fraction of the product obtained on polymerization of styrene with a heterogeneous catalyst system were determined for the purpose of determining the best conditions for copolymerization studies. The best reaction temperature at atmospheric pressure was found to be about 70°C. The initial ratio of triisobutylaluminum to titanium tetrachloride, if above 3: 1, did not influence the yield of isotactic product appreciably. The addition of lithium aluminum hydride to the catalyst resulted in a slight improvement of vield of isotactic polymer. In the titanium trichloride‐triisobutylaluminum catalyst system, preheating the two catalyst components prior to the addition of solvent and monomer led to improved Activity. Polymerization carried out under conditions of minimum swelling resulted in a lesser amount of amorphous product and improved yield of crystalline fraction. This was accomplished by the use of a nonswelling solvent and the controlled addition of monomer. Maintaining triisobutylaluminum concentration above a given level by stepwise addition during the polymerization greatly increased the activity of the catalyst. In the trichloride system, preheating, together with the use of Nujol as a solvent, controlled monomer addition, and stepwise addition of triisobutylaluminum improved the yield from in average of 0.4 to 6.0 g. of polymer per gram of titanium sa

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512906

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractElectron‐microscopic examination discloses the existence of globular formations, or micelles, in thermosetting resins, varying in apparent diameter from 400–900 A. These micelles are seen in thin sections, in preshadowed carbon replicas, in shadowed plastic strips revealed in profile, and as shadowed individuals. Micelles are abundant in phenolic, diallyl phthalate, and epoxy resins, and comparatively rare in silicones. The existence of micelles is in accordance with the theories of Houwink and Stäger, who consider that polymerization proceeds most rapidly at specific points in the resin; and explains the discrepancies between theoretical and observed tensile strengths. At least in the case of phenolics, micelles appear to arise in filaments formed in the polymerization process. The occurrence of linear arrays is in accordance with this mechanism of micelle forma

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512907

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractA few years ago, Singer, following Huggins' method of treatment of high polymer in bulk phase, derived an equation of state for monolayers of large, threadlike molecules. Davies and his co‐worker defined a quantity ω as a measure of flexibility of a polymer chain in the interface, where ω =z– 2 (zis the coordination number of the unit in the postulated two‐dimensional quasi‐lattice in the interface), assuming that each segment in a chain has exactly two positions in which its two neighbors in the chain must fit whenz= 2. Using this definition, they have developed their discussion as to flexibility of polymer chains at the interface. It is one of the purposes of this note to point out that their definition of ω is lacking in its theoretical background. Nevertheless, the values ofzobtained from the observed force‐area relations seem to afford a reasonable order of magnitudes for various types of polymer molecules, in accordance with other data on the flexibility of the polymer chains. Another purpose of this note lies in clarifying the origin of the just‐mentioned contradiction. The reason why the values ofzappear, at first sight, to give a good representation of the degree of flexibility of polymer chains, lies in the remarkable difference in molecular configurations between the “condensed” and “expanded” states at the interface. In conclusion,zor ω resembles the empirical parameter μ often used in the discussion on thermodynamic properties of polymer solutions. Careful analysis of this value is necessary before conclusions can be drawn about the structural characteristics of polymer molecules and the intra‐ and intermolecula

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512908

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractA microcolumn for fractionation by precipitation chromatography is described. It operates in conjunction with a continuous paper‐strip fraction collector, and has been used successfully to fractionate milligram quantities of polysarcosine dimethylamide. Polymer which can either be labelled or dyed may be determined directly on the strip by scanning methods. A semi‐empirical theoretical consideration of the column has resulted in the followimg molecular weight vs. volume relationship (for the case of a single constant volume solvent‐precipitant mixing chamber):\documentclass{article}\pagestyle{empty}\begin{document}$ M = \left[ {\frac{{KT_2 }}{{\sigma e^{ - {V \mathord{\left/ {\vphantom {V G}} \right. \kern-\nulldelimiterspace} G}} + \tau - T_2 }}} \right]^2 $\end{document}whereT2is the temperature at the, bottom of the column,Gis the volume of the mixing chamber, and τ and (σ+τ) may be identified with the Flory temperatures of solvent and precipitant, respectively. This has been found to be a close fit to published data for the fractionation of polystyrene. A comparison of exponential and constant solvent gradients shows that the former are advantageous for very broad distributions, the latter fo

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512909

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractBei der Emulsionspolymerisation des Styrols wurde durch Anwendung von öllöslichen Startern bzw. durch rein thermische Polymerisation die Bildung der Radikale aus der Wasserphase in das Monomere verlegt. Hierbei ergab sich eine beträchtliche Erhöhung der Polymerisationsgeschwindigkeit gegenüber der Polymerisation in homogener Phase, die nur durch die Isolierung einzelner wachsender Ketten in Latexpartikeln bedingt sein kann. Dass trotz paarweiser Erzeugung der Radikale in der Öphase Latexpartikel entstehen, die nur eine wachsende Kette enthalten, wird auf eine verhältnismässig rasch verlaufende Diffusion der primär gebildeten niedrigmolekularen Radikale aus der Öphase in die Wasserphase zurüchgeführt, von wo sie dann einzeln in Mizellen bzw. Latexpartikel eintreten könuen. Der Einfluss einer solchen intermicellaren Diffusion niedrigmolekularer Radikale—womit die Isolierung in Mizellen bzw. Latexpartikeln nur mehr für makromolekulare Radikale vollständig wäre—auf die Abbruchsgeschwindigkeit in der Emulsionspolymerisation bei Kettenübertragung wird diskutiert. Für die thermische Styrolpolymerisation ist ein Diradikalmechanismus auf Grund der Unter suchungsergebn

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203512910

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY