bluuebunny/crossref_metadata_2025_split huggingface dataset:
Complex formation and reversibility in copolymerization
Authors: Walling Cheves 
Published: April 2003

AbstractBarb's data4–6 on the copolymerization of styrene and sulfur dioxide are reviewed and shown to be in agreement with a scheme in which styrene‐sulfur dioxide complexes are not involved, but in which attack of a growing chain on sulfur dioxide is a rapidly reversible process at all temperatures, while, at higher temperatures, addition of a chain ending in sulfur dioxide to styrene becomes reversible as well. Eact for the loss of SO2 is estimated as lying between 4 and 14 kcal., while a chain ending in a sequence of styrene units reacts with SO2 at least 100 times as readily as with styrene. A similar interpretation is made of the ethylene‐carbon monoxide copolymerization,14 in which addition of CO appears to be a reversible process, since the amount of CO in the polymer increases with total pressure. Some other systems in which reversibility of chain propagation might be expected to affect copolymer compositions are pointed out.
Molecular configuration of gelatin
Authors: Gouinlock E. V. , Flory P. J. , Scheraga H. A. 
Published: April 2003

AbstractIntrinsic viscosities, light scattering turbidities and dissymmetries, and sedimentation constants have been determined for each of two high molecular weight gelatin fractions in 1 M KCNS, pH 6.5, at 30°. Their weight‐average molecular weights and z‐average radii of gyration were 6.0 × 105 and 280 A., and 3.8 × 105 and 240 A., respectively. The ratio [η]M/(r2)3/2, after allowance for the influence of molecular weight heterogeneity, approximates the accepted value of the viscosity parameter Φ. The values of \documentclass{article}\pagestyle{empty}\begin{document}$ {{M(1 - \bar \upsilon \rho )} \mathord{\left/ {\vphantom {{M(1 - \bar \upsilon \rho )} {NS_{0\eta 0} }}} \right. \kern-\nulldelimiterspace} {NS_{0\eta 0} }}(\overline {r^2 } )^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} very nearly agree with the normal value of the parameter P for the frictional coefficient when the experimental errors, molecular weight heterogeneity, and a possible small amount of selective binding of KCNS are taken into account. Similarly, the ratio \documentclass{article}\pagestyle{empty}\begin{document}$ {{NS_0 [\eta ]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} \eta _0 } \mathord{\left/ {\vphantom {{NS_0 [\eta ]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} \eta _0 } {M^{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} }}} \right. \kern-\nulldelimiterspace} {M^{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} }}(1 - \bar \upsilon \rho ) $\end{document} is almost equal to, though somewhat lower than, the normal value of Φ1/3P−1 if the same factors are taken into account. The molecular dimension ratio \documentclass{article}\pagestyle{empty}\begin{document}$ ({{\overline {r_0^2 } } \mathord{\left/ {\vphantom {{\overline {r_0^2 } } M}} \right. \kern-\nulldelimiterspace} M})^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} $\end{document} computed for the unperturbed gelatin molecule is indistinguisahble from that for various synthetic polymers. The ratio of \documentclass{article}\pagestyle{empty}\begin{document}$ (\overline {r_0^2 } )^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} $\end{document} to the value calculated assuming free rotation is 1.8 to 1.9, which indicates a degree of chain flexibility similar to that occuring in synthetic polymers. We conclude that the configurational character of the gelatin chain in aqueous media is not much affected by its polar linkages or by intramolecular hydrogen bonding.
Precision viscometry of polymer solutions
Authors: Kooy J. , Hermans J. J. 
Published: April 2003

AbstractThe article describes a method for measuring times of efflux in a capillary viscometer with an accuracy of 0.003 sec. A film is taken of the moving meniscus together with a synchronous clock. The temperature of the thermostat bath is controlled to within 0.001°C. by means of a Wheatstone bridge which contains temperature dependent resistances. Experimental results obtained with a polystyrene sample in toluene show no systematic deviation from linearity in the ηsp/c vs. c curve between 2 × 10−3 and 3 × 10−5 g./ml. The same curve for a sample of polymethacrylate in water shows a sharp maximum at about 10−4 g./ml.
A direct analytical test of the Flory‐Schulz distribution in nylon 6 type equilibrium polymers. Preliminary communication
Authors: Hermans P. H. , Heikens D. , Van Velden P. F. 
Published: April 2003

AbstractThe validity of the Flory‐Schulz distribution of chain length in equilibrium polymers produced from ϵ‐caprolactam and water (Nylon 6) over a DP range from ∼14 to ∼90 is tested by determination of the content of monomer (ϵ‐aminocaproic acid, ACA) by means of a chromatographic technique. Experiments show general agreement with a simple theoretical relationship (P̄n1 = N, where P̄ = number average DP of chains, n1 = number of ACA molecules, and N = total number of chains), required for equilibrium if equal reactivity of all functional groups independent of chain length is assumed. Moderate deveiations from this relation, which seem to occur at higher DP values (P̄ ∼ 90) require further investigation.
Polyphenyl
Authors: Edwards Gerald A. , Goldfinger George 
Published: April 2003

AbstractA substance indentified as polyphenyl1,2 has been obtained by the condensation of paradichlorobenzene using the Wurtz‐Fittig reaction. The viscosity behavior of polyphenyl is unusual. The curves obtained by plotting specific viscosity divided by concentration versus concentration pass through a maximum at very low concentrations, reaching a constant value at a concentration of about one percent. In the region of the maximum, the specific viscosity divided by the concentration is dependent on the rate of shear, increasing with decreasing rate of shear.
The preparation and characterization of block copolymers
Authors: Woodward A. E. , Smets G. 
Published: April 2003

AbstractBlock copolymers have been synthesized by heating a polymer, containing peroxidic linkages, in the presence of another monomer. The peroxide groups were introduced into the first polymer by initiating the controlled polymerization of its monomer with phthalyl peroxide. Separation of the block copolymers from the two parent homopolymers was made possible by their different solubilities in selected solvents or their mixtures. Polystyrene (Mn = 1.00 × 105), prepared at 75°C. in bulk with 0.5% phthalyl peroxide, initiated the polymerization of methyl methacrylate at 100°C. in benzene solution. The two block copolymer components isolated were found by infrared analysis to contain 22 and 30% polystyrene with number average molecular weights of 4.3×105 and 3.0×105, respectively. Block copolymers were also obtained by heating styrene in benzene at 85°C. with polyvinyl acetate (Mn = 0.60 × 105), prepared in benzene solution at 70°C. with 0.5% peroxide. A 39% vinyl acetate‐61% styrene block copolymer was isolated and found to have a molecular weight of 1.65×105. Intrinsic viscosities, μ values, and κ′ values for the block copolymers and related homopolymers were determined and are discussed in terms of composition, molecular weight, and poly‐dispersity. Other experiments indicated that styrene‐phthalyl peroxide polymers were unable to initiate vinyl acetate or vinylpyrrolidone polymerizations at 100°C. in significant amounts; this behavior is interpreted in terms of the stability of the radicals formed.
Molecular weight of polyvinyl acetate by light scattering and viscosity techniques
Authors: Chinai S. N. , Scherer P. C. , Levi D. W. 
Published: April 2003

AbstractA viscosity‐weight average molecular weight relationship was obtained for fractionated polyvinyl acetate in a thermodynamically “good” solvent acetone at 30°C. This relationship is represented by [η] = 8.6 × 10−5M. The value of the root‐meansquare end‐to‐end distance is approximately three times as large as the theoretical value for a chain with completely free rotation. The values of the osmotic second virial coefficient indicate the polymer molecules are expanded beyond their random flight dimensions. Consideration of the thermodynamic interactions in “good” solvent results in approximately constant values for A2M/[η] and A2M2/(r2)3/2. The average value obtained for the Flory universal constant is 1.98 × 1021.
Acrylonitrile polymerization in homogeneous solution
Authors: Thomas W. M. , Gleason E. H. , Pellon J. J. 
Published: April 2003

AbstractPrevious kinetic studies of acrylonitrile polymerization in bulk disclosed unexpected features that were associated with the heterogeneous nature of the system. In the present work, polymerization was carried out in homogeneous solution, principally in dimethyl formamide. Polymerization rate in dimethylformamide was dependent on the square root of the azo initiator concentration and approximately on the three‐halves power of the monomer concentration. Over‐all activation energy was 21 kcal./mole. Rates were slow in this solvent and molecular weights were low. Chain transfer activity of several liquids was estimated by substituting them for part of the dimethylformamide. Contrast between results in the homogeneous and heterogeneous cases is explained as due to removal by solvent of any opportunity for radical burial or catalyst enrichment. Standard kinetic treatments do not explain quite adequately the details of rate and molecular weight dependence on monomer. It appears that sluggish radicals are formed by chain transfer to solvent. A kinetic scheme is proposed to account for these observations.
Bis‐type modifiers in polymerization. II. Comparison of effectiveness of various compounds in emulsion butadiene and bulk styrene polymerizations
Authors: Costanza A. J. , Coleman R. J. , Pierson R. M. , Marvel C. S. , King Charles 
Published: April 2003

AbstractThe present paper describes the preparation and evaluation of the effectiveness as modifiers of a number of compounds of bis‐type structure—principally aryl disulfides—in bulk styrene and emulsion butadiene polymerizations. This work endeavors to explore some of the objectives described in the first paper of this series, and deals primarily with attempts to gain quantitative information on the effect of the nature and location of substituting groups with respect to the dissociating bond. The compounds examined include both those containing reactive groups attached and those lacking such groups. A number of the preparations are now compounds. Evaluations in 50°C. bulk styrene were carried out with the objective of eliminating the complications of the diffusion factor always present in emulsion systems. Generally speaking, the correlation between effectiveness in bulk styrene and 50°C. emulsion butadiene was quite good, though there were exceptions. It was found that the modifier activity of many compounds in emulsion butadiene could be enhanced by predispersing them in the aqueous phase—presumably a result of minimizing the importance of diffusion rate. Some of the modifiers were also tested in a low temperature butadiene emulsion system. Aryl disulfides continue to offer the most promise from the standpoint of combining the features of attaining high transfer constants and ease of incorporating desired reactive groups. Some compounds had adequate activity in emulsion butadiene polymerizations for use as practical modifiers. However, it has not yet been established that these compounds cleave to give one‐half the molecule on each end of the butadiene polymer chain, as has been done for styrene polymers.
Activity of counter ion in polyelectrolyte solutions
Authors: Kagawa Ikumi , Katsuura Kakuji 
Published: April 2003

AbstractThe activity of silver ion was measured potentiometrically with various sample solutions of silver or silver‐sodium salt, prepared from three different kinds of carboxymethylcellulose, for the purpose of elucidating these several points: dependence of the activity coefficient of counter ion upon the concentration of polyelectrolyte in salt‐free solutions; influence of the silver content of the sample upon activity coefficient; salt effect on activity coefficient; and dependence of activity coefficient upon the degree of neutralization. These experimental results indicate that the characteristics of polyelectrolyte solutions are in many respects quite different from those of simple electrolyte solutions. The applicability of the theory proposed by Ōsawa, Imai, and Kagawa is discussed in some detail, although the discussion is restricted to the salt‐free system only.
Viscosity measurements in branched silicones
Authors: Charlesby A. 
Published: April 2003

AbstractExposure to high energy radiation offers a means of producing controlled branching in long chain polymers. Branched silicone polymer molecules were obtained by exposing linear molecules to high energy radiation. The increase in weight‐average molecular weight calculated theoretically from the radiation dose was compared with the value deduced from measurements of intrinsic and bulk viscosity, ignoring the effect of branching. The ratio of these measurements show the apparent reduction in molecular weight (as measured by viscosity methods) when branched molecules are present. In particular it is found that the reciprocal bulk viscosity decreases uniformly with degree of branching (or crosslinking) until the gel point, when the weight‐average and bulk viscosity become infinite.
An intrinsic viscosity‐molecular weight relation for polyacrylonitrile
Authors: Cleland Robert L. , Stockmayer Walter H. 
Published: April 2003

AbstractWeight‐average molecular weights and intrinsic viscosities in dimethyl formamide at 25° have been measured for four unfractionated low‐conversion acrylonitrile polymers covering the molecular weight range 30 to 250 thousand. The results follow the equation:
Viscosity, sedimentation, and light‐scattering properties of fraction of an acid‐hydrolyzed dextran
Authors: Senti F. R. , Hellman N. N. , Ludwig N. H. , Babcock G. E. , Tobin R. , Glass C. A. , Lamberts B. L. 
Published: April 2003

AbstractDextran produced by Leuconostoc mesenteroides NRRL B‐512 was acid‐hydrolyzed and fractionated, yielding a series of fractions from which 24 were selected that ranged in molecular weight from 17,700 to 9.5 million. Light‐scattering and viscosity measurements were made on all fractions, and selected fractions were characterized by endgroup determinations and velocity ultracentrifuge measurements. Branching in these dextran fractions was evidenced by the progressively decreasing slope of the curve of logarithm of intrinsic viscosity plotted against logarithm of molecular weight, attaining a value of 0.11 at M = 107; by the upward curvature of the log‐log plot of sedimentation constant against molecular weight; and by the relatively large values of k′ in the Huggins specific‐viscosity equation for the high‐molecular fractions. Assuming Lansing‐Kraemer molecular‐weight distributions for the dextran fractions and using sedimentation data to furnish β, the measure of breadth of the distributions, physical characterizations were corrected for polydispersity. For molecular weights below 100,000, [η] = 1.0 × 10−3 Mv0.50. In the range 18,000 < M < 400,000 S200 = 0.0251 M00.44. The constant Φ′, of the Flory‐Fox theory, corrected for polydispersity of the fractions, was found to be 55.2 × 1021, which is larger than the value reported for linear polymers. It is concluded that the ratio of root‐mean‐square radius and hydrodynamic radius effective in viscosity differs for branched and linear molecules. The quotient (Φ′)1/2/P′ also appears to be significantly smaller for dextran than the value reported for linear molecules. Increase in Φ′, for dextran above the value previously assumed necessitates recalculation of data of Wales, Marshall, and Weissberg for g, the ratio of mean‐square radii of branched and unbranched dextran molecules.
Shear dependence of viscosity of alfin polyisoprene
Authors: Golub M. A. 
Published: April 2003

AbstractThe shear dependence of viscosity of alfin polyisoprene in dilute benzene solutions at 25°C. was studied over a wide range of molecular weights. The polyisoprene was prepared initially to amolecular weight of about 4,500,000, and a number of portions of the polymer were allowed to degrade to various intermediate molecular weights down to about 200,000 followed by stabilization at these particular molecular weight levels. This procedure provided a wide range of molecular weights without recourse to the usual fractionation. Inherent viscosities were measured in an Ostwald‐Fenske viscometer at rates of sher from about 1000 to 10,000 sec.−1 and at concentrations from about 0.05 down to 0.01 g./dl. Some data were also obtained in a series of similar viscometers of different radii. It was found that both the inherent and the intrinsic viscosities of the Alfin polyisoprene depend strongly on the rate of shear, the effect increasing with increasing molecular weight. Moreover, the shear dependence of the inherent viscosity is best expressed by an equation involving both a linear and a quadratic function of the gradient. The experimental data were examined from the standpoint of Katchalsky's proposed method for obtaining simply and rapidly the zero shear viscosity from measurements in an Ostwald‐type viscometer. According to this method, a plot of ts/t vs. P2R2, where ts and t are the flow times of the (Newtonian) solvent and (non‐Newtonian) solution, P the applied pressure, and R the radius of the capillary, should be linear, and the intercept of this line at P2 = 0 or R2 = 0 gives the reciprocal of the relative viscosity at zero shear. The agreement between the zero shear viscosities obtained by the Katchalsky method and from the conventional viscosity–shear curves was only fair. Above a molecular weight of about 280,000 the Katchalsky values are consistently smaller than the corresponding values obtained from the viscosity–shear curves, and furthermore this discrepancy increases with molecular weight. Because of this discrepancy, an attempt was made to modify the Katchalsky equation, so as to bring the respective zero shear viscosities in to better agreement. It was found that an anlogous equation, calling for a linear plot of ts/t vs. PR, provided a rather accurate measure of the zero shear viscosity.
Graft polymerization and branching
Authors: Voeks John. F. 
Published: April 2003

AbstractAn equation has been derived from a generalized set of polymerization reactions relating the branching fraction (ratio of new polymer bound to substrate to total new polymer) to various rate constants and reactant concentrations. Data from the literature are cited to illustrate various aspects of the equation. It is suggested that branching and grafting data can be correlated by a rather obvious extension of the Q and e systems.
Mastication of rubber. II. Interpolymerization of natural rubber and neoprene on cold milling
Authors: Angier D. J. , Watson W. F. 
Published: April 2003

AbstractGraft copolymerization of rubber and neoprene has been effected by cold mastication. Experimental evidence is based on the properties of the gels produced, solubilities of the sol fractions, and vulcanization of the neoprene component by magnesium oxide. Mechanisms of branching and gelling of neoprene and rubber‐neoprene systems are discussed. The utility of selective precipitation for detection of graft polymers is outlined.
Rupture of rubber. II. The strain concentration at an incision
Authors: Thomas A. G. 
Published: April 2003

AbstractThe strain distribution around the tip of an incision in a thin test‐piece of highly elastic material is considered. Using the results of a previous paper, relations between this strain distribution and the over‐all forces or strains are derived for two particular types of test‐piece. Experiments designed to check the theory are described, and agreement is found to be satisfactory. The theory is extended qualitatively to the case where the test‐piece is taken to the point of rupture, and experiments are described which confirm the approximate relation derived. The relevance to tearing and to the previously proposed tear criterion is discussed.
Stress relaxation of peroxide and sulfur vulcanizates of natural rubber
Authors: Berry J. P. , Watson W. F. 
Published: April 2003

AbstractThe stress relaxation behavior of peroxide and sulphur vulcanized natural rubber has been investigated using a relaxometer of new design. The peroxide vulcanizates do not degrade significantly in vacuo and degrade by an exponential decrease in stress with time in oxygen. The vulcanizates from the two sulfur recipes used give stress relaxation in vacuo and more rapid relaxation in oxygen. A theoretical analysis provides the shape of stress–time curves anticipated for various modes of network degradation. The present data and other published results are consistent with a mechanism of scission at the crosslinks and not at random along the chains. The peroxide vulcanizates are interpreted as decaying by a first‐order scission of crosslinks and the sulfur vulcanizates by first‐order scission of two types of crosslink. The uncertainties still present in interpreting stress relaxation data are discussed.
Equilibrium distribution of molecular weights in noncyclic polymerizations
Authors: Harris Frank E. 
Published: April 2003

AbstractThe equilibrium molecular weight distribution in noncyclic condensation polymers depends upon the free energies of the various species in solution as well as upon the multiplicity of ways the polymerizable groups can be combined. It is shown that, although both the ideal solution theory and the Flory‐Huggins formula for the free energy of the solution lead to the well‐known molecular weight distribution obtained originally by Flory and by Stockmayer, only a restrictive group of deviations from ideality will lead to this distribution. Distributions were calculated using Guggenheim's expression for the free energy of mixing of the polymeric species, together with two alternative expressions for the free energy of the pure, separate, polymers, and in one case the distribution deviates markedly from the ideal solution result. It is concluded that reasonable deviations from ideality may significantly affect the equilibrium molecular weight distribution.
Vinyl polymerization. VI. Polymerization of acrylonitrile in the presence of substituted benzoyl peroxides and dimethylaniline
Authors: Imoto Minoru , Takemoto Kiichi 
Published: April 2003

AbstractThe solution polymerization of acrylonitrile was carried out by dilatometry at 40 ± 0.02°C. Using benzene as solvent, and various substituted benzoyl peroxide derivatives as initiator, experiments were made both in the presence and in the absence of dimethylaniline. It was found that the initial rate of polymerization. R0, could be expressed by:

The values of k0 were determined. The applicability of Hammett's rule are observed. In the presence of DMA the reaction constant ρ was positive, but in the absence of DMA ρ was negative. Molecular weights of polymers obtained were nearly reversely proportional to the initial rate of polymerization.