ISSN:0022-3832    

DOI:10.1002/pol.1953.120100601

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe diffusion of alcohols, glycerol, phenol, formic, acetic and butyric acids through four species of Indian timbers in the water‐saturated condition has been studied and the results reported. In contrast to several inorganic ions, Fick's law is obeyed by the organic molecules in the concentrations studied. As is to be expected, the diffusion in the axial direction is several times that in the other directions. The speed of diffusion decreases rapidly with the molecular weight of the substance and the density of the wood. While in the case of the alcohols the logarithm of the diffusion constant varies as the molecular weight with the acids the diffusion constant is proportional to the molecular weigh

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100602

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractInitial rates of polymerization in the presence of benzoyl peroxide as initiator have been determined for methyl methacrylate, vinyl acetate, and vinyl chloride in order to determine the order of reaction with respect to the monomer concentration. In the case of methyl methacrylate, the order of reaction is 1 if benzene is used as solvent; withtert‐butylbenzene, the order of reaction is more complex, and can be interpreted by a “complex” formation mechanism (Mark‐Josefowitz) or by cage effect (Matheson). In the case of vinyl chloride and vinyl acetate in the presence, respectively, of ethyl chloride and ethyl acetate as solvent, the order of reaction has been evaluated to 3/2vs.monomer concentration. On the contrary, addition of benzene, even in small quantities, produces a strong decrease in rate of polymerization in the case of vinyl acetate, and makes it illusory to determine the order of reaction at high monomer concentrations. Preliminary results using azo‐bis‐isobutyronitrile as initiator for vinyl acetate with benzene as solvent have shown that the considerable influence exerted by benzene in the previous case cannot be attributed to a difference of rate of decomposition of the peroxide only. The results are interpretd by the mechanism of chain‐transfer reactions on the solvent, with formation of radicals from which the relative stability is different from that of the g

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100603

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractMeasurements on flow birefringence of solutions of polyvinyl chloride in cyclohexanone revealed that the angle of orientation increases with decreasing concentration of the solution. That this surprising effect was not due to constructional or experimental errors was demonstrated by results obtained with polystyrene, which were in agreement with literature data.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100604

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractNous utilisons la méthode de transmission pour calibrer la diffusion lumineuse. Nous vérifions en utilisant des solutions d'indices de réfraction différents que la correction de réfraction est pratiquementn2pour l'intensité diffusée, l'intensité incidente à travers la cellule devant être corrigée empiriquement pour une réfraction due à la légère divergence du faisceau primaire. A partir de ce calibrage, nous obtenons pour le rapport de Rayleigh du benzène à 20°C. et pour λ 4358 A.R= (48,4 ± 1,5)10−6cm.−1. Pour les mesures de dissymétrie dans la cellule commerciale semioctogonale “Pyrocell,” nous montrons la présence de réflexions totales pour les solutions d'indice de réfraction ≥ 1,41, réflexions qui peuvent être éliminées aisément en plaçant un verre absorbant dansle fond de la cellule. D'autre part, nous calculons la correction à apporter à la dissymétrie du fait des réflexions de Fresnel quand le faisceau lumineux

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100605

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100606

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe configurations of flexible macromolecules are discussed with particular emphasis on some problems arising in the theory of the volume effect. The main points considered are: (1) the relationship between the Kuhn statistical chain element and the carbon bond length; (2) the assumption that a polymer chain is equivalent to a collection of independent beads normally distributed with respect to the center of gravity (“Gaussian gas” model); (3) the distribution of segments of a polymer chain with respect to the center of gravity; (4) the theory of the execluded volume for plane models of a polymer molecule; (5) the relationship between the excluded volume and the local density of polymer segments; (6) the influence of the solvent on the excluded volume; (7) polymer configurations and viscos

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100607

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100608

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100609

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100610

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY