摘要:

AbstractA new method for the photochemical initiation of polymerization of vinyl compounds in aqueous solution is described. The photochemically active species is an ion pair complex of the formula Fe3+X−(X−= OH−, CI−, N−3, etc.). The light absorption by the ion pair leads to an electron transfer causing reduction of the cation and oxidation of the anion to an atom or free radical X. The latter leads to the initiation of polymerization in accordance with X + CH2CHR→XCH2CHR. The kinetics of the reaction were studied by the measurement of: (a) ferrous ion formed (colorimetrically), (b) monomer disappearance (by titration and by weighting the polymer), (c) the chain length of the polymer (in the case of methyl methacrylate). The dependence of the quantum yield on the light intensity, light absorption fraction, and the concentration of vinyl monomer and ferrous ion added initially was investigated. A complete mechanism, both with regard to the formation of free radicals and the polymerization reaction, was put forward involving: (1) light absorption, (2) a primary dark back reaction, (3) dissociation of the primary product, (4) a secondary dark back reaction, (5) initiation of polymerization by free radicals, (6) propagation of polymerization, and (7) termination by recombination of active polymer endings. The mechanism was verified by the experimental results and some constant ratios were estimat

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070211

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe intrinsic viscosity of cellulose xanthate solutions was studied as a function of the electrolyte content of the solvent, and found to decrease sharply with increase in electrolyte concentration. All electrolytes tested except sodium and lithium hydroxides produced essentially the same reduction in intrinsic viscosity for solutions of equivalent ionic strenghts, indicating that the effect was largely one of interaction between the solvent ions and the charged xanthate groups. Hydroxides induced a greater viscosity reduction. The reason for this was not fully resolved; however, indications were obtained that the hydroxides, in addition to behaving as electrolytes toward the charged xanthate groups, also interact with the hydroxyl groups on the parent cellulose chain.Light scattering measurements, as well as data on the variation of the intrinsic viscosity with molecular weight in various solvents, showed that the change in intrinsic viscosity with electrolyte concentration could be accounted for by a change in configuration, or degree of coiling of the molecule. Calculations indicated that in pure water cellulose xanthate should approach a rigid rod configuration whereas in 6% caustic coiling occurs and the molecule resembles more a random configuration.

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070212

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractWe have noted some correspondences in the theories of high polymer solutions. This article is divided in two independent sections: (I)Osmotic pressure.The second virial coefficients for polymers of the pearl‐necklace type are given and discussed in two limiting cases—the dumbbell and the infinitely polymerized molecule having a definite length. The variation of the coefficients against the polymerization is predictable from these limiting cases (Fig. 1). Attention must be paid to the manner of taking the (abscissa). The case of infinite polymerization can be considered as corresponding to polymers of a compact single‐body type such as globular proteins. Thus, an interesting correspondence in the second virial coefficients can be judged for the pearl‐necklace and the compact single‐body type of polymers. The general feature of the coefficient is also discussed. (II)Intrinsic viscosity.The relation between the two methods (Kirkwood‐Riseman and Debye‐Bueche) for intrinsic viscosity of high polymer solutions is discussed. Because the respective fundamental equations are equivalent to each other, we may choose whichever of these two me

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070213

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070214

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractMany linear polymers containing water‐attracting groups spread uniformly at the airwater interface. The spreading property of polymethyl methacrylate is due to the ester groups which serve as anchors and promote spreading. The spreading of polystyrene, although it is a pure hydrocarbon, appears probably to be due to the end groups in each polymer molecule, introduced at the termination of the chains which act as anchors and facilitate spreading.The surface pressure extended by the films of the high polymers is a sort of two‐dimensional swelling pressure. The distinguishing feature of these films is their high compressibility in the rectilinear portion of the F–A curve.The limiting areas for F–A curves are not independent of the concentrations of spreading solutions as might be expected. The primary cause of this phenomenon in the case of high polymers appears to be a more or less coherent sponge‐ or felt‐like structure which develops at high concentration. The linear polymers, like polystyrene, become coiled up statistically and at higher concentration the coils become interlocked and produce an imperfectly

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070215

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractL'étude de la cellulose régénérée des composés de gonflement que fournissent avec NH3liquide la cellulose native et la cellulose mercerisée conduit à la définition de deux formes correspondantes aux matières de départ: les celluloses IIIα et IIIβ. L'action de l'eau fournit avec le réseau IIIα un réseau élargi et avec IIIβ conduit à la cellulose II. Les mailles des celluloses IIIα et IIIβ toutes les deux monocliniques, présentent

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070216

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070217

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070218

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070219

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070221

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY