摘要:

AbstractOff‐meridian small‐angle x‐ray interference maxima and multiple orders of small‐angle interference maxima have been observed for certain synthetic high polymer fibers including polythene, polyamides, polyethylene terephthalate, and polyvinyl alcohol. The observations indicate that the ordering of the structures responsible for small‐angle diffraction may be two‐ or three‐dimensional rather than one‐dimensional and that such ordering must extend over larger volumes of space than previously published data would indicate. The fibers must be given relaxation treatments to form the structures that result in small‐angle maxima except for polythene in which they appear merely on orientation. The relaxation treatments increase the crystallite size as shown by large‐angle pictures and modify the positions and shapes of the small‐angle maxima. An increase in the degree of relaxation increases the intensity of the interference and increases the magnitude of the interplanar spacing except for polyvinyl alcohol, in which the interplanar spacing is not affected. Samples of 66 nylon, which varied in molecular weight from 26,000 to 200,000 gave identical small‐angle interference patterns within

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070501

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractIn this paper a simple method is described for determining the moment of disappearance of soap micelles during the emulsion polymerization of styrene by measuring the electrolytic conductivity during the polymerization.

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070502

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractHeretofore it has been assumed that, under the same experimental conditions of time and magnitude of applied pressure, all amorphous polymers have equal viscosities at their tack temperatures. Further evidence is obtained with a number of polymers in support of the theory. As a nonequilibrium property characterizing high polymers, tack temperature thus belongs in a category with brittle points, second‐order transition points, and softening temperature

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070503

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe effect of isooctane andn‐dodecane on the reduced viscosity of aqueous solutions of a polysoap, derived from poly‐2‐vinylpyridine (D.P. 2000) by partial quaternization withn‐dodecyl bromide, was determined. It was found that the reduced viscosity of polysoap solutions decreased linearly with added hydrocarbon, indicating that the polysoap molecule coils are contracted by the solubilizate. This contraction is ascribed to an increase in the van der Waals' attractive energy furnished by the solubilized hydrocarbon molecules.When the saturation limit of the hydrocarbon was reached, addition of more hydrocarbon caused no further decrease in the reduced viscosity. This phenomenon furnishes a new method for measuring solubilization of hydrocarbons by polysoaps. Solubilization values of isooctane obtained by this procedure were compared with those found previously by the vapor pressure method. The close agreement confirms the validity of both experimental methods.The efficiency of solubilization and the percentage depression of the reduced viscosity were not sensitive to changes in the polysoap concentration. The following differences in the solubilization behavior of the polysoap toward isooctane and dodecane were observed: (1) isooctane was solubilized to a greater extent than dodecane; (2) the maximum reduced viscosity depression obtainable with isooctane was greater than that obtainable with dodecane; (3) gram for gram, the dodecane was the more efficient at depressing the reduced vi

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070504

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractAs a step in the general development of a kinetic theory of sulfur vulcanization, rate data published by Zapp and co‐workers on the accelerated vulcanization of Butyl rubber are analyzed. Rate constants are calculated, some with remarkable accuracy, and these compare admirably with those previously calculated by the writer from data on unaccelerated Buna S vulcanization by Blake and co‐workers. In accordance with theory, acceleration is found to be due to a decrease in activation energy, which more than compensates for a considerable decrease in frequency factor predicted by theory. As in the case of unaccelerated cure, the reaction order is unity, at least initially, and reflects the disappearance of the sulfur during the reaction. The rate determining step is the reactionwhere Z· is a radical derived from the accelerator. Although the sulfur combines with the polymer and with zinc oxide, these two entities thus do not enter into the rate controlling step. The importance of classifying polymer reactions according to the participation or nonparticipation of the polymer in the rate control is stressed. Tentative arguments are advanced for kinetic and chemical details of the chain reaction between ZSSSSSSSS·. and rubbers. Some parallels are drawn between vulcanization, polymerization of sulfur, and the

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070505

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractIn this paper we have suggested that the interaction between the hemes of hemoglobin is due primarily to entropy effects associated with configurational changes in the molecule as a whole. In hemoglobin the four hemes appear to occur in paris, and the estimated interaction between members of the same pair would correspond to an entropy effect of 12 calories per degree or more, which is roughly the same as the entropy change which occurs when a mass of rubber equal to the half weight of hemoglobin is stretched to between twice and three times its initial length. Such an entropy change would account for the value ofn= 1.9 observed in the oxygen and oxidation equilibria of hemoglobin split in halves by urea. The configurational hypothesis here proposed would at once explain the close similarity between the oxygen, carbon monoxide, and oxidation equilibria of intact hemoglobin, for x‐ray studies indicate that the same configurational changes accompany all three reactions. It would also account for the difference of solubility between hemoglobin and oxyhemoglobin, as well as a number of other matters. Some new data on the oxygenation of sickle‐cell anemia hemoglobin are presented and discussed in connection with the hypothesis.The further suggestion is made that the Bohr effect may be due, not to changes of bond type in the heme globin linkage as proposed by Coryell and Pauling, but to changes in the position and environment of certain acid groups resulting from changes in the configuration of the hemoglobin molecular as a whole. This would explain the essential identity of the Bohr effect for oxidation, oxygenation, and combination with carbon monoxide, as well as other things.It is finally suggested that the kind of entropy effect postulated in hemoglobin may play a role in the activation of substrates by enzymes more generally.As we have pointed out, the suggestions made in this paper are highly speculative and their value will depend largely on the extent to which they point to new experiments. Among many questions which arise are these: Is there any configurational change which occurs in myoglobin, with only a single layer of polypeptide chain, when it is oxygenated? What happens to the interaction and the Bohr effect when hemoglobin is caused to combine with a variety of reagents which react with specific groups in the molecule? Is there any significant change in the dipole moment of the hemoglobin molecule when it combines with oxygen and changes shape? These and other questions, if they were answered, would be highly pertinent to the suggestions presented in this pa

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070506

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractFollowing a brief review of some earlier theories of filler reinforcement that were based, at least partly, on thermodynamic treatments, a reinforcement equation is derived by a combination of thermodynamics and the elasticity theory of large strains. It consists of an elastic energy term and a surface energy term, and is given by:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm R}.{\rm E}. \cong [(1 - \rho )E/2][(1 + n\pi d^3 /6V_1 )^{2/3} - 1] - n(\Gamma \pi d^2 - \delta )$$\end{document}In it, the “reinforcement energy,” R.E., is defined as the energy of the filler‐rubber mixture less that of the separate components. This is related to a fractional heat term (p) arising from the “expansion” of the rubber due to filler incorporation, the Young's modulus (E) of the rubber, the number of particles (n) of filler (considered as existing initially in an aggregate), the ultimate particle diameter (d), the volume of rubber (V1), the total energy of immersion per unit surface area (Γ) of the filler in the rubber, and the mean cohesion or aggregation energy per particle (δ) between the particles in the original aggregate.The significance of R.E. in terms of actual reinforcement is discussed; R.E. is regarded as negative measure of reinforcement. Estimates are made of the magnitudes of the two energy terms and of the surface energies Γ and δ. These indicate that in mixtures containing very active fillers (such as carbon blacks in natural rubber), Γ is of the order of 100 ergs per sq. cm. and the surface energy term is dominant. A crude estimate indicates that δ is much less than Γπd2for very active fillers, that these quantities may be of the same order of magnitude for less active fillers, and that δ may be larger than Γπd2for inert fillers. In the last two cases, the surface energy term loses much or all of its dominant character.Predictions from the reinforcement equation are examined in the light of available experimental results, and some apparent discrepancies are discussed. Expressions are given for corrections that need to be applied to the equation when particle dispersion is incomplete, or when the latter is a function of the

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070507

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractPolymeric phthalyl peroxide was used as an initiator for the polymerization of styrene at 60°C. The peroxide is initially partially insoluble in the monomer, but decomposes and becomes soluble during the course of the polymerization. The intrinsic viscosity of the polymer formed increases with increasing conversion and at about 65–70% conversion becomes higher than would arise from a monoradical‐initiated polymerization proceeding at the same

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070508

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractFor solutions containing rod‐shaped polyelectrolytes and their counterions only, the Poisson‐Boltzmann equation can be solved explicity without the usual assumption of the Deybe‐Hückel theory. At charge densities corresponding to half‐neutralized polyacrylic acid a large proportion of monovalent counterions is located close to the polyion even in solutions as dilute as 1/800 ba

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070509

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe dielectric dispersion of cellulose nitrate solutions in acetone was studied over a frequency range of 100‐500 KC by a resonance method using substitution techniques to measure the capacitance. An abnormally narrow region of dispersion was found which could not be reconciled with the Debye type of absorption. By assuming the solvated chain molecule to have the form of a loosely held random coil it was possible to explain the experimental, dispersion curve on the basis of resonance absorption.Speculation on the similarity of the shape of the dispersion curves to those found for distribution by fractional precipitation suggested a possible correlation between them. In the case of at least one polymer the derived correlation proved satisfactor

ISSN:0022-3832    

DOI:10.1002/pol.1951.120070510

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY