摘要:

AbstractHydroxyethylated polyvinyl alcohols (HEPVA's) containing 12, 19, and 35% combined ethylene oxide were prepared by a heterogeneous reaction between dry polyvinyl alcohol (PVA) and liquid ethylene oxide. Another sample containing 18% was prepared by a more nearly homogeneous reaction in the presence of water. These derivatives may be analyzed satisfactorily by the modified zeisel method of Morgan. The properties of the HEPVA's are briefly described. Reaction of HEPVA withp‐toluenesulfonyl chloride showed that secondary hydroxyls were tosylated along with the primary and that the two reactions cannot be separated kinetically. This method, useful in estimating the primary hydroxyl content of hydroxyethylcellulose, cannot be applied to HEPVA. The stability of the tosylates indicated, however, that in derivatives containing up to 35% combined C2H4O2ca.1/2 ethylene oxide per vinyl alcohol unit, no polyethylene glycol chains were present and all combined ethylene oxide existed as individual hydroxyethyl groups distributed along the PVA backbone. Introduction of ethylene oxide into PVA increased the reactivity of residual secondary hydroxyls toward chemical reagents by destroying the normal high degree of hydrogen bonding and making adjacent domains more accessible for reaction. Very noticeable differences in properties were observed between HEPVA's prepared under differing conditions of heterogeneity. Two such polymers of similar ethylene oxide content showed quite different extents of reactions, susceptibility toward swelling agents, and x‐ray diffraction diagrams. These differences are attributed to a more random distribution of hydroxyethyl groups along the PVA backbone in the product of the more homogeneous reaction which leads to a more disordered sys

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110301

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractGutta, the polyisoprene hydrocarbon obtained from gutta percha or balata, is usually considered to differ from rubber in that gutta is atrans‐isomer and rubber acis‐isomer of polyisoprene. Most of the data on the basis of which these structures have been assigned come from x‐ray diffraction pictures of polycrystalline polymer. Single crystal data have not been published, although such data would provide more detailed information. Chicle gutta has been shown to be a lower molecular weight modification of gutta from gutta percha. As a consequence of its lower molecular weight chicle gutta is a granular, free‐flowing powder, whereas gutta percha gutta is horny and tends to clump together. Because of its physical characteristics and lower molecular weight, chicle gutta was used first in an attempt to grow single crystals of gutta. By working with dilute solutions, well‐shaped single crystals of chicle gutta as large as 0.35 mm. in the long direction were obtained. From gutta percha Pahang, crystals 0.10 mm. long were isolated. Crystals could be grown either by slow diffusion of solvent or by cooling a supersaturated solution. Crystals were found to be optically anis tropic and to exhibit parallel extinction when examined under crossed Nicols with the polarizing microscope. Crystals obtained were of the alpha modification

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110302

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe importance of sample preparation is demonstrated with examples of techniques based on (1) evaporationin vacuo,(2) casting from solvent or solvent mixtures, (3) ultrasonic disintegration. Attention is drawn to the “sheaf‐like” arrangement of the microfibrils and to other aspects of the texture. There is evidence of periodicities, but these are considered to vary with the preparation, and may be a consequence of the helical arrangement and “rope‐like” character of the bundles of microfibrils or of a tendency to form a wo

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110303

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe transition temperatures (TG) of unfractionated vinyl acetate polymers increase from 17° to 26° as the molecular weight increases from 14,000 to 104,000 and from 26° to 28° as the molecular weight increases from 104,000 to 1,120,000. The minimum molecular weight above which increase in molecular weight does not appreciably changeTGis about 100,000.TGincreases linearly with the reciprocal of the square root of the molecular wei

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110304

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractFor a particular sample of polystyrene, different osmometric estimates ofMnhave been reported. The possibility that the difference is due, in the one case, to permeation of the membrane by low molecular weight polymer has been carefully considered. It is shown that this can not be the explanation. The difference is in some way associated with chemical differences in the membranes used. Apart from these considerations of error, the significance of the number‐average molecular weights of the unfractionated polymers of commerce is shown to be more acutely dependent upon the detail of the low molecular weight end of the distribution than may be realized. The present calculations are based upon a realistic estimate of the low molecular weight polymer content of commercial polymer

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110305

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractWhen a dilute pyridine solution of vinyl chloride polymers or copolymers is heated and a few drops of alcoholic hydroxide are added to the hot solution, a dark brown color develops. The response of vinyl chloride polymers in this reaction is much more intense than that of most other organic compounds, probably due to the conjugated double bonds produced in the main chain through the loss of hydrogen chloride. In addition to straight degradation of the polymer, the formation of an isocyanine dye is suggested by a mechanism which, besides pyridine and the polymer, involves the alkali alkoxide as a reactant.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110306

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractA study is made of the behavior under constant shear stress of several carefully characterized samples of polyisobutylene. The materials used are whole polymers and fractions obtained from these by dractional precipitation. As a first step in the characterization, the intrinsic viscosity of each is determined. It is shown that the samples cover a molecular weight range from 1 × 105to 1 × 106. To provide a more detailed characterization, sedimentation equilibrium experiments are performed with several of the polyisobutylenes. These experiments yield values of several average molecular weights for each polymer, from which data an approximation to the molecular weight distribution can be made. It is pointed out that the whole polymers of isobutylene are very polydisperse. The viscosity‐average molecular weights calculated from these experiments are in good agreement with the results of the intrinsic viscosity measurements. The viscoelastic behavior of some of these polymers is then studied by means of creep and recovery experiments. The melt viscosity is determined in two ways, from flow during creep and from the amount of nonrecoverable deformation after elastic recovery. The elastic recovery of the polyisobutylene samples is analyzed in some detail. A method for the reduction of data taken at several temperatures to a standard temperature, previously used for dynamic‐mechanical properties and stress relaxation data, is shown to be applicable to elastic recovery data. Furthermore, the results of creep and recovery experiments can be superimposed in favorable cases. The steady‐state elastic compliance is evaluated, and errors in its determination discussed. The results would seem to indicate that this quantity depends, at least in part, upon the degree of polydispersity of the polymer. This dependence appears to mask any direct variation with average molecular weight. Finally, it is shown that an average retardation time is directly proportional to the melt viscosity of the

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110307

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractButadiene popcorn polymer reacted readily with oxygen to produce a yellow to orange colored product. The apparent over‐all activation energy for the reaction averaged 16.7 kcal. Using the reaction with oxygen as a measure of the degree of unsaturation, the glassy type butadiene popcorn polymer was found to be more saturated that the earlier generation popcorn from which it was grown. The induction period which precedes the logarithmic growth of the polymer when placed in the presence of monomer increased as the oxygen content of the seeds increased. No increase in growth activity was ever attained by exposing the seeds to oxygen. Short exposures of the seeds to oxygen up to three hours at room temperature had no effect on the growth activity of the seeds. No correlation could be found between the seed growth activity and the degree of unsaturation as determined by the oxidation reactio

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110308

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110309

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110310

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY