摘要:

AbstractA quantitative analysis of the 725 cm.−1doublet in the infrared spectrum of polyethylene is given and used to check the “row” model of polyethylene, as it naturally crystallizes from drawn melt. This analysis depends on a new interpretation of the 725 cm.−1doublet, according to which the 730 cm.−1component has its transition moment along theacrystallographic axis, and the 720 cm.−1component along thebaxis. The amorphous polymer gives only a band at 720 cm.−1. The analysis in certain cases enables the amount and orientation of the amorphous component of the polymer to be determined. From similar considerations, variations in the relative intensity of the two peaks in the course of drawing unoriented polyethylene

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157911

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe random chain model for polyelectrolytes proposed by Kuhn, Kunzle, and Katchalsky is considered. The thermodynamic and configurational properties calculated by Katchalsky and Lifson are shown to be somewhat in error because they have used an incomplete expression for the stretching free energy of the polymer. The agreement of the theory with experiment is not substantially affected in most regions of interest.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157912

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractRecently the depolymerization of addition polymers has been treated in terms of four elementary reactions: initiation, propagation, transfer, and termination; analogous to those reactions which operate in the polymerization process. It is the transfer process which, according to its relative importance, gives rise to differences in polymers in the monomer yield, in the ratevs. conversion behavior, and in the molecular weightvs. conversion behavior. The transfer process is assumed to operate through the abstraction of a hydrogen from the polymer chain by a radical. By substituting a deuterium for the hydrogen at selected points in the polymer chain, the amount of the transfer process should be decreased due to an isotope effect. Two deuterated polymers were made from α‐ and β‐deuterated styrenes and their depolymerization behavior studied. In the case of the α‐deuterostyrene polymer the results are compatible with a ½ decrease in the rate of the transfer process and also an increase in the rate of the propagation. The results with the β‐polymer imply an increase in both the transfer and propagation rates. The data obtained indicate that in polystyrene the intermolecular transfer process is mainly responsible for the fall in molecular weight of the polymer residue during depo

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157913

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractA study has been carried out on the emulsion polymerization of isoprene in an attempt to evaluate the relative rate of the crosslinking reaction and its variation with temperature. From the relation between primary chain length and gel formation during polymerization, the following values were obtained for the relative crosslinking rate constant,i.e., ratio of the velocity constants of the crosslinking and propagation reactions.TextTemperature,°C.K=kx/kp603.4 × 10−5704.3 × 10−5805.2 × 10−5The above data lead to a calculated value for the difference in the activation energy between the crosslinking and the propagation reaction (Ex−Ep) of 5.0 kcal. From these data and the known value of the propagation rate constant, it is possible to calculate the following absolute rate expression for the crosslinking reaction itself:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_x = 8.5 \times 10^6 \exp \{14,800/RT\} $$\end{document}It is noteworthy that the relative crosslinking rate in isoprene polymerization is only about one‐sixth that found for butadiene (K= 2 × 10−4at 60°C.) apparently owing largely to a higher steric factor. Hence longer chains are possible for polyisoprene before network formation leads to gelation. In the Mutual Recipe, the rate per particle for isoprene polymerization is about three times as fast as for butadiene, although it is still short of the rate found in the ideal low te

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157914

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractWhen polymers of two different chemical species are dissolved in a common solvent the resulting solution usually separates into two phases. No obvious relation between phase separation and chemical nature of the monomeric units was observed. Solute molecular weight, temperature, and nature of the solvent were shown to be factors in determining the course of phase separation. A concept of phase separation is suggested which involves low entropy of mixing, greater attraction between like than unlike species of solute, and density differences between solvated polymer molecules.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157915

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractA chemical kinetic interpretation of the rheological behavior of high polymers has been proposed, in which the polar force of segments locks the adjacent segments in neighboring molecules in a similar way to crosslinking in vulcanized rubber. The change of such a crosslink caused by the thermal motion of segments and by external stress on the sample gives rise to rheological phenomena, such as the relaxation of stress or strain. The elasticity or viscosity of high polymers is related to the equilibrium crosslinkage which is affected not only by the temperature change but also by external stress. The structural viscosity, the yield point, or the effect of solvent on elasticity or on viscosity can also be understood according to this interpretation. The theoretical treatment gives many equations previously found in experiments: the equation for relaxation of deformation or stress,i.e., the four‐element‐model equation, the Dienes' equation with respect to the temperature dependence of elasticity of polyvinyl chloride, or Rabinovitch's equation for structural viscos

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157916

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractA quantitative study of the pyrolysis ofp‐xylene at temperatures from 795° to 920° at low pressures has been made using a flow system at low contact times. A mechanism is postulated to account for the principal products. The primary rate controlling reactions are the dissociation of either a CH bond in the methyl side chain or a CC bond from the ring to the methyl group, the activation energies of which are 79 and 82 kcal., respectively. Evidence is presented for the existence of the intermediatep‐xylylene molecule, and for its formation by disproportionation from the initially formedp‐methylbenzyl radicals. The copolymerization ofp‐xylylene with maleic anhydride or chloroprene

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157917

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractApparent first‐order rate constants and activation energies for the alkaline hydrolysis of polyvinylpyrrolidone, polyactam, vinylpyrrolidone‐maleic acid copolymer,N‐isopropyl‐γ‐valerolactam, butyrolactam, and pyrrolidone‐N‐acetic acid were determined in order to study the influence of structure on the stability of the lactam ring. It was found that the behavior toward alkaline hydrolysis of polyvinylpyrrolidone closely resembles that of its low molecular analogueN‐isopropyl‐γ‐valerolactam. It has been shown that a carboxyl function substituted near the lactam ring has a favorable influence on the ease of hydrolysis. Alkyl substitution on the lactam nitrogen, however, makes the lactam more resista

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157918

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe equilibrium between a linear polymer molecule and a binary solvent mixture in which it is immersed has been treated. An equation has been derived relating the resulting molecular expansion to the thermodynamic parameters for the ternary system and to the solvent composition. Intrinsic viscosity measurements are reported for polystyrene fractions in three mixed‐solvent systems: methyl ethyl ketone‐methanol, carbon tetrachloride‐cyclohexane, and benzene‐cyclohexane. Intrinsic viscosities measured for polystyrene fractions in critical consolute mixtures agree with those found in single poor solvents at the analogous Theta points. Intrinsic viscosities have been measured over ranges of mixed‐solvent composition for the second and third solvent mixtures mentioned. Poor agreement with theory is observed for the former, but the more extensive measurements in benzene‐cyclohexane mixtures agree very well with theoretically calculated intrinsic

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157919

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractSorption of NO2by cellulose acetate proceeds by a process of solution, diffusion, and reaction governed by Henry's law, Fick's law, and first order kinetics with respect to the consumption of NO2. It appears as though water is the primary substrate with which NO2reacts in the acetate film. The pseudo‐unimolecular rate constant for films conditioned at 50% RH seems to be about 10 ± 5 × 10−3sec.−1. The solubility of NO2in dry film increases with increasing degree of acetylation. With the present data the diffusion coefficient and solubility in moist films cannot be determined separately, but only jointly as a parameter involving the product of one by the square of the other. Improved experiments designed to yield precision during the later stages of the sorption process should yield separate values of the two co

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157920

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY