摘要:

AbstractA study has been made of the flow behavior of solutions of a single sample of polystyrene in five different solvents in both the Newtonian and non‐Newtonian regions. The concentration range covered was approximately 0‐20% by weight, and the temperatures were 20, 30, 40, and 50°C. By application of the Ree‐Eyring theory it was found possible to represent the observed data in terms of two flow units, and to obtain from the parameters of the Ree‐Eyring equation the effective hydrodynamic volume occupied by the polymer in solution, εv, wherevis the volume fraction of polymer and ε an effective volume factor. For any given solvent ε varies from [η]/2 atv= 0 to ε =ca.4 atv∞, the volume fraction at which εv= 1 and the viscosity becomes infinite; and, except in very dilute solutions, ε is essentially independent of the temperature. Again, for any given value ofv, ε is a function of the nature of the solvent only betweenv= 0 andv= 0.04. Above the latter concentration ε is completely independent of the solvent in which the polystyrene is dissolved, and becomes merely a function of the solution concentration. These results indicate that chain entanglement in solution, if it does occur, can take place only below a concentration ofv= 0.04. Abovev= 0.04 no entanglement can be present, and the configuration of the polymer chain, as reflected in the effective volume they occupy, is governed only by the nonspecific factor of the space available for occupancy by each molecule. As this space decreases with increase in concentration, the polymer molecule is forced to reduce its effective volume by coiling into a tighter mass. This process continues until εvbecomes equal to unity, at which point the state of tightest coiling is reached without change in the nature of the flow. In the latter state the polymer molecule is shown to occupy a volume 2 to 3 times, and to have a cross section 1.26 to 1.44 times, that of

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713101

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractTheoretical formulas for the intrinsic viscosity and viscoelastic properties of some model branched molecules in dilute solution are calculated by means of the normal coordinate method of Rouse modified to include hydrodynamic interactions. The calculations are exact except for the usual approximation of the hydrodynamic interaction by the Kirkwood‐Riseman formula. The ratio of the intrinsic viscosity of a branched molecule to that of a linear molecule of the same weight is found to vary almost as the square root of the ratio of the mean square radii, instead of as the latter ratio to three‐halves power, as has been postulated before. It is proposed that this square root relation is applicable in general to branched molecules of all types. Several sets of experimental data in the literature are shown to agree well with this hypothe

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713102

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractAn X‐ray study has been made of partially benzylated cellulose obtained from mercerized cotton yarn, in accordance with a recently developed technique. This study reports the formation of a new crystal lattice for benzylcellulose with a degree of substitution less than 1. This new lattice is indicative of a considerable distension of the original cellulose II unit cell present in the mercerized yarn. Attempts to benzylate ramie fibers under the same conditions resulted in destruction of the fibrous structure by the treatment. Application of heat and tension were found to cause considerable improvement in crystallinity and degree of crystallite orientation of the benzylated cotton. Application of pressure in preparing the sample for X‐ray analysis in the usual manner was found to affects the X‐ray diffraction pattern, due possibly to distortion of the greatly distended (101) interplanar sp

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713103

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe theory of bulk viscosity as developed for the liquid state was applied to amorphous high polymeric systems. The isothermal volume contraction, the dependence of shear viscosity, and the fictive temperature of quenched high polymeric substances are all related to the bulk viscosity and explained by this theory. Simple representations are given for compressibility, bulk modulus, shear modulus, thermal expansion coefficient, and heat capacity, all of which are necessary to discuss the bulk viscosity. The theory has been compared with the experimental results for natural rubber, polystyrene, polyisobutylene, and polyester.

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713104

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe spherulitic structures in very thin films of linear plolyethylene and poly‐oxa‐1,4‐bis(dimethylsilylene) benzene have been examined by a variety of optical techniques. These techniques included bright field electron microscopy and bright and dark field light microscopy. Polarization effects in these polymers were also examined using the light microscope. The polarization phenomena were most marked in the poly‐oxa‐1,4‐bis(dimethylsilylene) benzene, presumably as a result of the benzene ring. The negative polyethylene spherulites showed a banded structure in all types of illumination. It was shown that the banded structure exhibited between crossed Nicols is due to low positive birefringence while the black cross was due to zero amplitude effects. All the optical phenomena could be interpreted in terms of a model which proposes that a given spherulite radius is coposed of a stack of crystallites whose refractive index ellipsoids (a) have centers along the radius, (b) have optic axes which make a fixed angle with the spherulite radius, and (c) are twisted as they go out along the radius so that the displacement is proportional to the twist. The model also emphasizes the presence of interstitial amorphous polymer. On the basis of this model the crystallites in polyethylene spherulites were shown to have a twist length of about 4 μ and to have their major refractive index axes (chain directions) inclined at an angle of 75° to the sphe

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713105

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractIt is shoen that all everage exterior and interior branch lengths of A‐R‐B2type condensation polymers are equal in length. Because of this, each configuration in the less random statistical model V is an average of all similarly constructed configurations found in the more variable statistical model. Consequently, certain structural properties of the statistical polymer can be examined by using all the configurations of a givenx‐mer from the less random model V. The statistical model and partially “debranched” statistical model were used to represent glycogen and amylopectin, respectively. These polymers were theoretically degraded by “phosphorylase” and “amylo1,6‐glucosidase.” Rabbit muscle glycogen behaves as a statistically formed polymer. On the other hand, rabbit liver glycogen behaves as if a large amount of 1,3‐linkages were present in its structure and/or behaves as lif it had been debranched by an enzyme such as the R‐enzyme. When compared to corn amylopectin, wheat amylopectin behaves as if more of its inteerior branches had been removed. Myrbäck and Sillén's statistical model and Bourne and Peat's pseudo‐amyl

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713106

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe authors have found experimentally that the initial slope of a Trautman plot of data obtained from sedimentation‐velocity experiments yields thez‐average molecular weight of the solute components. It is also well known that the weight‐average molecular weight is obtainable from such a plot. Equations are derived which permit the calculation of the individual concentrations and molecultar weight for unknown twocomponent paucidisperse systems. The experimental results on various two‐component protein mixtures are compared to known values. It was found that the ratio of the weight concentrations of two components must be within about one to five for accurate results. It may be possible to extend the method to multicomponent systems. One could then rapidly determine the size distribution of synthetic and natural heterogeneous p

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713107

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractAn index of the molecular weight dispersity of a polymer is afforded by the ratio of viscosity‐average molecular weights in two different solvents. The index is proportional to the weight‐ to number‐average molecular weight ratio. The simplicity and ease with which this index can be experimentally obtained is bought to a certain extent by loss of reliability. Extensions of the proposed procedure leading to characterization of the molecular weight distribution are disc

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713108

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractIt has been found that the polymerization of acrylonitrile dissolved in water proceeds easily in the presence of hydrogen peroxide and iron(III) salts. The kinetic investigation of this reaction shows that it is second order with respect to the monomer. The rate of reaction invreases with the concentration of hydrogen peroxide and of iron(III) salt but it decreases with an increase in the concentration of hydrogen ions. The average molecular weight of the formed polymer was determined by viscosity measurements. The degree of polymerisation increases with the concentration of the monomer and hydrogen ions, but decreases with an increase in the concentration of hydrogen peroxide and iron(III) salt. The reaction is inhibited by dissolved gaseous oxygen. Under otherwise similar conditions, the rate of the decomposition of hydrogen peroxide is considerably decreased in the presence of the acrylonitrile compared with its catalytic decomposition by iron(III) salts without acrylonitrile present. The amount of hydrogen peroxide decompsed on the average is more than two molecules per molecule of the formed polymer. The experimental data are briefly discussed in relation to a plausible reaction mechanism.

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713109

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe molecular distributions arising in the coupling of linear polymers are treated in this paper. The distributions are similar to those arising in single‐stage polycondensations, but are more complex. Multi‐stage polycondensations lead to extremely complex distributions. Frequently the distributions of coupled polymers are quite similar to those of the geometrical. However, if the polymer chains to be coupled are quite different from the geometrical in distribution, or if very unsymmetrical coupling agents are used, the coupled polymers may be much narrower than geometrically distributed polymers. In the limit, it is possible to achieve essentially monodisperse polycondensates using multi‐stage condens

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203713110

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY