bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidation and grafting of benzyl and ethyl cellulose
Authors: Gleason E. , Stannett V. 
Published: April 2003

AbstractThe preparation of graft copolymers of benzyl and ethyl cellulose was attempted through the initiation of vinyl polymerization by the cellulose ether hydroperoxides. The benzyl and ethyl cellulose ether hydroperoxides were prepared in solution by oxidizing with air. The polymer underwent severe chain degradation concurrently with hydroperoxide formation. The relative rates of these reactions differed for the benzyl and ethyl cellulose ether and also depended on the nature of the solvent. As a result, the hydroperoxide content of the polymer could be increased by lengthening the oxidation time, but the number of hydroperoxide groups per chain increased much more slowly. With the use of ethyl cellulose hydroperoxide as initiator, a kinetic study of styrene polymerization was made. Rates of hydroperoxide decomposition were also measured so that the efficiency as initiator could be determined. These rate data indicated an efficiency of 60–90% and considerable chain transfer to the hydroperoxide groups. In the preparation of graft copolymer the amount of actual graft was determined to be very small. Poor yields of graft copolymer were attributed to an unfavorable competition in the reactions of initiation and chain transfer and to the degraded chain length of the cellulose ether hydroperoxide. Substantiating evidence for the occurrence of nongrafting initiation and transfer reactions came from an infrared study of low molecular weight polystyrene initiated with α‐isobutoxyethylhydroperoxide.
On the mechanism of emulsion polymerization of styrene. II. Polymerizations in soap solutions below and above the critical micelle concentration and some remarks on the kinetics of emulsion polymerization
Authors: Van der Hoff B. M. E. 
Published: April 2003

AbstractEmulsion polymerizations of styrene were carried out at different phase ratios. The initial soap concentration was varied from below to above the critical micelle concentration (CMC). Above the CMC the number of particles formed agrees with values calculated from the Smith‐Ewart theory. As the soap concentration is reduced below the CMC the number of particles decreases sharply. In this concentration range the number of particles is independent of the amount of initiator but depends strongly on soap concentration. Kinetic features suggest a similarity between particle formation in these polymerizations and in homogeneous precipitation of inorganic insoluble salts. The coefficient of variation of particle diameter distribution below the CMC is about 2.5% and at high soap concentration about 15%. Bimodal distributions are obtained when the initial soap concentration is near the CMC. The initiation efficiency of persulfate is calculated from the rate and degree of polymerization and also from the number of particles formed. The efficiency increases from 0.2 to 0.6 with decreasing persulfate concentration. When the particles are smaller than about 0.12 μ, polymerization kinetics follow the Smith‐Ewart theory. Values are reported for the monomer concentration in the particles and for the constant of propagation. Larger particles exhibit a gel effect, i.e., more than one radical can coexist in a particle for a significant lenght of time. From polymerization rate data and molecular weight measurements the rate constants for the transfer reaction to monomer and for termination are calculated. The latter constant is found to be two to three orders of magnitude smaller than values obtained in solution polymerization. The difference is attributed to the high viscosity of the interior of the particles which causes the termination reaction to be diffusion‐controlled.
Pyrolysis of polyolefins
Authors: Wall Leo A. , Straus Sidney 
Published: April 2003

AbstractThe differences in thermal decomposition behavior previously observed between linear and branched polyethylenes have been explored experimentally by investigating and comparing the rates of volatilization of a series of twenty polymers. Similar differences were observed between linear and branched polypropylenes. The linear material in both cases exhibited behavior characteristic of a random decomposition, while the branched material did not. Other materials studied included high pressure polyethylene; low pressure copolymers of ethylene with propene, butene, and pentene‐1; and polymers and copolymers prepared from diazoalkanes. Systematic deviations from random theory were found to occur with branching. The greater the branching, provided that the branches were longer than one carbon atom, the greater was the rate of decomposition and the more it was at variance with random theory. No quantitative theory accounting for these results is yet available. However, it seems that polymer branching enhances intramolecular transfer at the expense of intermolecular transfer. This is evidenced by the observed rate‐conversion curves, which are of a type similar to that found for polymers that decompose mainly into monomer.
The effect of molecular weight distribution on the rheological properties of polystyrene
Authors: Rudd John F. 
Published: April 2003

AbstractMelt viscosities were measured on 25 narrow molecular weight distribution (anionically polymerized) and 7 broad distribution (isothermally polymerized) polystyrenes ranging in molecular weight from 50,000 to 570,000. Measurements were made at temperatures between 200 and 250°C. and at shearing stresses of 120,000–1,400,000 dynes/cm.2 using a capillary‐type viscometer. Zero shear viscosity and non‐Newtonian constant was found to depend upon weight‐average molecular weight while high shear viscosity was found to depend upon some molecular weight between weight average and number average. Analysis of flow curves for two materials having the same zero shear viscosity but different weight average‐number average ratios indicated that the narrow distribution material had a higher high shear viscosity than the broad material pointing to lessened ease of fabrication. From flow data at different temperatures, apparent activation energies were calculated. Apparent activation energy was found to be independent of molecular weight above a molecular weight of 50,000 and to decrease slightly with increasing M̄w/M̄n ratio. The effects of plasticization and blending upon flow properties were also studied using samples to which 1% mineral oil had been added and blends of high and low molecular weight narrow distribution polymers.
Crystalline polyvinylcyclopropane, polyvinylcyclopentane, and polyvinylcyclohexane
Authors: Overberger C. G. , Borchert A. E. , Katchman A. 
Published: April 2003

AbstractVinylcyclopropane was polymerized with a catalyst of triisobutyla luminum and titanium trichloride and yielded crystalline polyvinylcyclopropane. The reaction of crystalline polyvinylcyclopropane with hydrogen bromide yielded an amorphous, bromine‐containing polymer. A bromine‐modified polyvinylcyclopropane, which was also amorphous and several other modified polymers were prepared. The pyrolysis of both 1‐ and 2‐cyclopentylethyl acetates yielded vinylcyclopentane, which was polymerized with catalysts of triisobutyl‐aluminum and titanium tri‐ and tetrachloride. Vinylcyclohexane was polymerized, and the properties of crystalline polyvinylcyclohexane were compared with those of the crystalline five and three‐membered pendant ring polymers.
Osmotic pressures of aqueous polyvinylpyrrolidone solutions
Authors: Cerny L. C. , Helminiak T. E. , Meier J. F. 
Published: April 2003

AbstractThe osmotic pressures of six well‐fractionated samples of polyvinylpyrrolidone were measured in aqueous solution in a Lucite‐block type osmometer. The molecular weights and interaction parameters were determined by employing the theory proposed by Maron for osmotic pressure. It was shown that for all of the fractions, a linear relation existed for ψ and y as predicted by the theory. This new method for expressing osmotic pressure data is compared with the more commonly used expression:

It was found that the molecular weights and T2 are in satisfactory agreement. However, the value ofg was not a constant equal to 0.25, but varied with the molecular weight. The expression for the osmotic pressure given by Maron's theory appears to be an accurate and rapid method of converting osmometric data to molecular weights.
The mechanism of polyvinyl chloride stabilization by barium, cadmium, and zinc carboxylates. II. Radioactive tracer studies
Authors: Frye Alfred H. , Horst Raymond W. 
Published: April 2003

AbstractPolyvinyl chloride deteriorates primarily by a zipperlike elimination of hydrogen chloride from the polymer and the concomitant formation of a colored and easily ozidizable polyene chain. Baum and Wartman have shown that the elimination is initiated by the rupture of certain especially labile carbon‐chlorine bonds. In Part I of this series, we presented infrared evidence to show that the barium, cadmium, and zinc salts of 2‐ethylhexanoic acid, when milled into polyvinyl chloride, react with the resin by an esterifying displacement of chlorine, and proposed that their stabilizing action arises, at least in part, from substitution of certain labile chlorine atoms with more stable carboxylate groups. In the present work we have prepared the barium, cadmium, and zinc salts of radioactive 2‐ethylhexanoic acid and have shown that when these salts are milled into polyvinyl chloride, and the films heat‐treated and then subjected to repeated dissolution in tetrahydrofuran and precipitation with methanol, the precipitated resin shows an effectively constant retention of radioactivity. Hence, the proposed esterifying displacement is unequivocally proved. We have also shown that the amount of radioactivity which is retained by the precipitated resin varies with the particular salt, the temperature, and duration of heat treatment, and that it qualitatively parallels the intensity of the 5.75‐μ band observed in Part I. Finally, we have shown that one function of the organic phosphites (frequently components in commercial stabilizers) is to render innocuous the chlorides of barium and cadmium, which otherwise exert a very deleterious action upon the resin, but which are inevitably generated by the interaction of eliminated hydrogen chloride upon the metal carboxylates.
Copolymers of vinyl chloride and some vinyl esters of acids derived from pinene
Authors: Marvel C. S. , Shimura Yukio , Magne F. C. 
Published: April 2003

AbstractHomopolymers of terpene‐derived vinyl monomers and copolymers of these with vinyl chloride incorporating varying amounts of the terpene‐derived monomers have been described. Copolymers incorporating 24–26% of terpene‐derived monomer were screened as rigid plastics. None of these comonomers resulted in an internally plasticized film when incorporated in the copolymer. A homopolymer‐copolymer blend exhibited limited compatibility. The use of an external plasticizer with these copolymer compositions appears to have merit.
Blue solutions of potassium in ethers as initiators of anionic polymerization
Authors: Dainton F. S. , Wiles D. M. , Wright A. N. 
Published: April 2003

AbstractIt is shown that freshly prepared, filtered, blue solutions of potassium in 1,2‐dimethoxyethane (DME) or in tetrahydrofuran (THF) initiate the rapid polymerization of styrene. For the K—DME system 100% yields of living polymer are obtained, whereas for the K—THF system, fractional yields of nonliving polymer are formed. By the application of rapid mixing and quenching techniques, minimum values of the rate constant of anionic propagation are obtained for the K—DME system at —78, 0, and 25°C. and for the K—naphthalene—THF system at 0°C. The true initiator in these blue solutions is considered to be a solvated, spin‐coupled, electron pair. The difference between the two systems and the probable kp values are discussed.
Application of an expanded copolymerization equation to the system styrene–fumaronitrile
Authors: Ham George E. 
Published: April 2003

AbstractApplication of the equations developed in the previous paper shows that the copolymer system styrene‐fumaronitrile obeys the equation:

where r1 = K—aaa/K—aab = 0.8, r1′ = K—baabaa/K—baabab = 0.3, and r1″ = K—babaa/K—babab = 4.0.
Polymerization with redox initiators. II. The system styrene–benzoyl peroxide–dimethylaniline at elevated temperatures
Authors: O'Driscoll K. F. , Schmidt J. F. 
Published: April 2003

AbstractKinetic measurements have been made on the bulk polymerization of styrene at 30 and 60°C. in the redox system dimethylaniline–benzoyl peroxide. From these measurements it has been ascertained that the kinetic behavior of this system at higher temperatures is the same as that at lower temperatures. The decomposition rate constant and the efficiency in initiating polymerization were determined. It has also been shown that neither the amine nor the products of the amine‐peroxide reaction affect the propagation of the polymerization.
Shear degradation of vinyl polymers in dilute solution by high‐speed stirring
Authors: Johnson William R. , Price Charles C. 
Published: April 2003

AbstractThe degradation of polyisobutylene and polystyrene resulting from high‐speed stirring of their dilute solutions has been investigated. Maximum degradation was obtained in “poor” solvents, at low temperatures and at highest possible rates of shear. The lower limit of the intrinsic viscosity reached for polyisobutylene in benzene solution was 1.30 as measured in cyclohexane at 30°. For polystyrene the lowest molecular weight attained is represented by an intrinsic, viscosity of ca. 0.75 in methyl ethyl ketone at 25°. The polymers were sheared in the presence of iodine and the amounts of iodine incorporated into the polymers measured radiochemically. The amounts of iodine incorporated during shear were of the same order of magnitude as the number of chain scissions calculated on the basis of the decrease in intrinsic viscosity.
Synthesis of optically active vinyl polymers by asymmetric induction. II
Authors: Schmitt George J. , Schuerch Conrad 
Published: April 2003

AbstractMaleic anhydride and l‐α‐methylbenzyl vinyl ether were copolymerized by a free radical mechanism in homogeneous solution to yield a levorotatory copolymer. Upon removal of the original asymmetric center by photobromination and hydrolysis, a dextrorotatory copolymer was produced. This reversal of the sign of rotation can be attributed only to an excess of one configuration in the chain backbone induced during the propagation step of the polymerization.
Branching in polymers. I. Network defects
Authors: Case L. C. 
Published: April 2003

AbstractThe problem of inactive chains in a polymer network is considered in this paper. It is shown that the previous treatment is only approximate. More rigorous treatments are derived here for random crosslinking of polymers which are initially either geometrically distributed in molecular weight or are monodisperse. The new treatments give values for active chain concentrations which are lower than those calculated by the approximate method. At high crosslink densities and for chains of molecular high weight initial, all methods yield approximately identical values.
Reaction kinetics and tacticity of macromolecules. I. Methacrylic acid—ester copolymers
Authors: Smets G. , De Loecker W. 
Published: April 2003

AbstractThree different samples of polymethyl methacrylate of different tacticities were prepared, the first by the conventional method in the presence of benzoyl peroxide as initiator (conventional polymer), the second by a pseudo‐ionic method with phenylmagnesium bromide in toluene solution (polymer A), the third photochemically at −20°C. in toluene in the presence of benzoin (polymer B). On the basis of their infrared spectra, polymer A corresponds to a syndiotactic structure, while polymer B must be considered as a mixture of conventional and isotactic polymers. These polymethyl methacrylate samples were hydrolyzed in concentrated sulfuric acid up to different degrees of hydrolysis by heating up at 60°C., isolated, and purified. The kinetics of the hydrolysis of the corresponding acid—ester copolymers were studied; the reactions were carried out in buffered aqueous solution at different degrees of neutralization. Polymer A hydrolyzes about four to five times faster than the conventional polymethyl methacrylate, while polymer B hydrolyzes very slowly and must contain configurations which are resistant to acid hydrolysis in these experimental conditions; this configuration is probably the isotactic one.
Polymer NSR spectroscopy. III. The rates of the propagation steps in the isotactic and syndiotactic polymerization of methyl methacrylate
Authors: Bovey F. A. 
Published: April 2003

AbstractBy measurement of peak areas in the α‐methyl region of the NSR spectra of 15% chloroform solutions of methyl methacrylate polymers prepared by free radical initiation over a 178° range of polymerization temperatures, it has been found that syndiotactic propagation becomes increasingly dominant as the polymerization temperature is decreased and that propagation tends toward randomness as the polymerization temperature is increased. We report the first experimental measurement of the difference in activation enthalpies and entropies for syndiotactic and isotactic monomer placement. It is found that there is no difference in the activation entropies of these processes, but that isotactic placement requires an additional activation enthalpy of 775 ± 75 cal./mole.
Studies on polyoxypropylene glycols. Part II. Derived thermodynamic functions for the systems: Polyglycols–methanol
Authors: Conway B. E. , Lakhanpal M. L. 
Published: April 2003

AbstractThe thermodynamic properties of the polyoxypropylene glycol fractions in methanol, experimentally determined as described in Part I, have been examined in terms of various statistical mechanical theories. The Flory‐Huggins interaction parameter χ has been calculated and enthalpic and entropic components of χ deduced from the experimental data. Deviations from the Flory‐Huggins theory are discussed. The thermodynamic excess functions for free energy and entropy of mixing are calculated, and it is concluded that strong orientation effects are operative in the polymer–solvent interaction, presumably through hydrogen bonding with the solvent. The hydroxylic endgroups on the short chain fractions play an important role in determining the thermodynamic behavior of the solutions. The role of orientation effects is examined by calculating the partial molar heat content and the partial molar entropy of the solvent and applying the theory of Münster for polymer solutions in which solvent orientation effects are operative. A semiempirical treatment, less arbitrary than that used by Münster, gives satisfactory results for polymer fractions of M. W. 150 and 1120.
Local regularity of chain substances. I
Authors: Miyake Akira , Chûjô Riichirô 
Published: April 2003

AbstractThe local regularity of chain substances composed of N linked elements, of which each can be in either of two states, the L‐configuration and the H‐configuration, is examined by means of statistical‐mechanical calculations. Introducing a virtual boundary energy at every boundary between the L‐regions, consisting of elements of the L‐configuration only, and H‐regions of H‐configuration elements only, we can deduce any average property of the chain from the logarithmic differentiation of the largest eigen‐value of the transition matrix. The average numbers of L‐ and H‐elements are NL = NB/(B + 1) and NH = N/(B + 1), respectively; that of L‐ or H‐parts is n = NLNH/N, and those of elements per L‐part and per H‐part are 〈l〉 = N/NH and 〈h〉 = N/NL, respectively, where B = exp {J/kT}, k is the Boltzmann constant and T the temperature. We can show the usual combinatory method gives the same results. Application of these relationships to a discussion of the stereospecificity of vinyl polymerization is referred to.
Active centers in the polymerization of ethylene using titanium tetrachloride–alkylaluminum catalysts
Authors: Feldman C. F. , Perry Eli 
Published: April 2003

AbstractA method was developed to measure the active centers in a titanium tetrachloridealkylaluminum catalyst system for the polymerization of ethylene. The method depends on the assertion that the active carbon atom of the growing chain is relatively basic and will react with alcohol‐O‐t. The tritium becomes incorporated in the polymer. The relationship used is N = AG/a, where N is the corrected active center concentration, A is the radioactivity of the polyethylene in counts/min./g., G is the polymer concentration at the time of sampling and a is the specific activity of the quench methanol‐O‐t in counts/min./mole. The data were corrected for the kH/kT isotope effect of 3.7 which was measured for the alcohol‐O‐t reaction. This isotope effect was unchanged over a wide range of molecular weights and reaction conditions. The basicity of the carbon on the growing polymer chain was proved by quenching the reaction with C14‐labelled alcohol. The resulting polymer was not radioactive. The values of N could be correlated with polymerization rates. Values of the active center concentration and polymer chain lifetime were calculated as a function of molecular weight using fractionated polymer. The centers are very heterogeneous and the lifetimes of polymer chains range from 1 to 30 min. (with an average of 4 min. for the particular conditions used). Calculated values of viscosity‐ (M̄v) and number‐average molecular weights as a function of time of reaction agreed well with the experimental data. Because of the long lifetime of some chains, a steady state in M̄v is not reached, and M̄v increases throughout the course of the reaction. Catalyst efficiency was calculated from a knowledge of N. The efficiency, which can vary from 0.3 to 15% based on the titanium, is a function of how the catalyst components are brought together. The value of N in these systems is about 10−3 to 10−4 moles/liter compared to 10−7 to 10−9 for the concentration of active species in free radical systems. The value of the propagation constant, kp, is comparable in both systems. It is concluded that the very rapid polymerization rate in these heterogeneous systems is due solely to high values of N. These high values of N argue against bimolecular termination of centers. The stability of the centers when refluxed under argon support this idea and cast doubt on chain termination via hydride ion transfer or transfer to solvent. The value for the activation energy of kp is 11.8 over the range of 40 to 68°C. The value of the activation energy for initiation of centers is deduced to be 11.8 kcal./mole, also.
Crystalline acrylic polymers. I. Stereospecific anionic polymerization of methyl methacrylate
Authors: Goode W. E. , Owens F. H. , Fellmann R. P. , Snyder W. H. , Moore J. E. 
Published: April 2003

AbstractIsotactic (type II)polymers of methyl methacrylate are obtained from anionic polymerizations initiated by organolithium compounds at low temperature ( −70°)in toluene solution. The presence of small amounts of various ethers leads to polymers of reduced isotacticity; the effectiveness of these ethers in disrupting stereospecificity can be related semiquantitatively to their Lewis base strength. Certain Grignard reagents also produce highly isotactic polymer of methyl methacrylate, while others lead to less stereospecific results. The nature of the inorganic component of such initiators appears to determine the steric course of the addition reaction. The formation of a magnesium halide–monomer complex may be involved.