bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulfur‐induced cis‐trans isomerization of polybutadiene
Authors: Bishop William A. 
Published: April 2003

AbstractBoth high cis‐1,4‐polybutadiene and high trans‐1,4‐polybutadiene were found to isomerize when heated in the presence of elemental sulfur. The kinetics of the sulfur induced isomerization of high cis‐1,4‐polybutadiene were studied over a wide range of temperature and sulfur concentration and found to obey a first‐order kinetic expression having an effective rate constant directly proportional to the initial sulfur concentration. The apparent activation energy was found to be 30.1 ± 0.4 kcal./mole. Isomerization was also found to be induced by dicumyl peroxide. A comparison of the mechanisms involved in the sulfur and peroxide induced isomerization indicate a basic difference in the nature of the initial interaction of the double bond with the sensitizing species. The initial interaction of the sulfur and the double bond is pictured as a π‐complex that decomposes to a freely rotating radical, whereas the peroxide induced isomerization is presumed to involve direct radical addition to the double bond.
γ‐Radiation‐initiated polyethenesulfonamide
Authors: Wiley Richard H. , Alvey F. B. 
Published: April 2003

AbstractThe rate of the radiation‐initiated polymerization of ethenesulfonamide, which is relatively high (1.25%/min.), is dependent on the 0.96 power of the intensity of the radiation. At increasing radiation dose levels the viscosity decreases and then remains constant indicating a balance between radiation‐induced degradation and branching. The polyelectrolyte character of the polymer is shown in both viscosity and light‐scattering data.
Interference microscopy of crystalline high polymers. Determinations of the thickness of single crystals
Authors: Wunderlich Bernhard , Sullivan Peter 
Published: April 2003

AbstractThe quantitative analysis of single crystals of polyethylene with the two‐beam interference microscope has been described. The thickness of single crystals formed at 87°C. is 134 A. The variation thickness is equal or less than 6 A. A general pattern of growth is discussed.
Elektronenspinresonanz‐untersuchungen an bestrahltem polypropylen
Authors: Fischer H. , Hellwege K.‐H. 
Published: April 2003

AbstractDie Untersuchung der Richtungsabhängigkeit der Elektronenresonanzlinien von bestrahltem orientertem Polypropylen erlaubt eine relativ sichere Bestimmung der gebildeten Makroradikale. Es wurde festgestellt, dass bei 77°K bei der Bestrahlung vorwiegend ein Radikal der Form
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entsteht, während bei Zimmertemperatur vermutlich ein Radikal vom Allyltyp der Struktur
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sich durch hohe Lebensdauer auszeichnet.
The concentration‐dependent diffusion of styrene in ethyl cellulose
Authors: Vanderkooi William N. , Long Merton W. , Mock Richard A. 
Published: April 2003

AbstractThe diffusion of styrene vapor in ethyl cellulose film has been studied as a function of styrene solubility in the film at 50°C. Methods and data are presented for determining the equilibrium solubility of styrene in ethyl cellulose as a function of vapor pressure at 50°C. The permeation rates of styrene vapor through 3‐mil film were determined under steady state conditions for various pressures of pure styrene vapor on one side of the film and vacuum on the other side. From a plot of permeation rates versus styrene solubility the diffusion coefficient was calculated as a function of concentration. Measurements made over a concentration range of 0 to 0.7 g. styrene/cm.3 of unswollen film show that the diffusion coefficient first increases rapidly with concentration, then goes through a maximum, and finally levels off at 10−7 cm.2/sec. In the limited range of 0.06 to 0.10 g./cm.3 the diffusion coefficient varies exponentially with concentration as has been reported for other systems in a similar range. However, such a functionality does not represent the present system over a broad concentration range. These results, if generally applicable to other systems, indicate that the nature of the diffusion process for organic vapors in polymers may be considerably more complicated than formerly supposed.
Kinetics of mutual radiation grafting of styrene in ethyl cellulose film
Authors: Mock Richard A. , Vanderkooi William N. 
Published: April 2003

AbstractA general procedure is described by means of which the kp/kt1/2 ratio can be determined for the graft polymerization of vinyl monomers in an organic substrate. The method takes rigorous account of the influence of monomer diffusion on the reaction kinetics. As an experimental example, the mutual radiation grafting of styrene onto ethyl cellulose film by use of 2‐M.e.v. Van de Graaff electrons to initiate free radical formation is described in detail.
Calculation of the thermodynamic properties of polyelectrolytes in the presence of salt
Authors: Alexandrowicz Z. 
Published: April 2003

AbstractThe potential and the activities in salt‐containing polyelectrolyte solutions are calculated by extending the treatment of Lifson and Katchalsky, which deals with rodlike polyelectrolytes in solutions to which no salt is added. An approximate procedure is employed, whereby the cylindrical volume element (per macroion) is divided into two shell‐like regions, as follows: In the outer shell, in which the drop of potential is relatively small, the exponential coefficient of the local ionic concentrations is expanded linearly and the Poisson‐Boltzmann equation may be solved in terms of Bessel functions. In the inner core, the coion concentration is assumed to equal zero, so that the problem reduces to the Lifson‐Katchalsky case of saltless solutions. The resultant potential leads to activities which resemble closely the recently formulated empirical law according to which the activities may be described simply as a superposition of “effective” ionic concentrations, contributed independently by the polymer and by the salt. The significance of the results may be appreciated when the fate of the ions which come from the salt is examined. It is then found that the coions, and the additional counterions as well, are accommodated mainly in the outlying regions of the volume element and fail to penetrate and influence the immediate surrounding of the polyion.
Osmotic and donnan equilibria in polyacrylic acid–sodium bromide solutions
Authors: Alexandrowicz Z. 
Published: April 2003

AbstractOsmotic and Donnan equilibria were measured in aqueous solutions of ionized polyacrylic acid and of sodium bromide. The results served to examine the validity of the previously formulated, “empirical” and “theoretical” formulas for the activities in mixed salt–polyelectrolyte systems (c.f. the preceding article). A very good agreement between the experiment and both formulas is found in case of the osmotic factor. The results obtained for the activity coefficient of the salt show a more limited agreement, and the validity of the theory seemingly does not extend—except as a very rough approximation—to the case of concentrated polymer solutions to which relatively small amounts of salt are added. Donnan and osmotic equilibria were also measured at a constant concentration of the external salt solution and the results obtained in the presence of an excess of salt interpreted in terms of the well known binding ratios (m′s – ms)/mpolymer and second virial coefficients, respectively. The former are found to increase in concentrated salt solutions, in agreement with the theory (which in this case differs largely from the empirical formula), whereas the latter are described adequately enough by the simpler empirical formulas. The limited nature with respect to both the validity and significance of constant binding ratios and second virial coefficients, is discussed.
The swelling of polymer systems in solvents. II. Mathematics of diffusion
Authors: Buckley Donald J. , Berger Martin 
Published: April 2003

AbstractData from complete swelling–time curves for crosslinked polymers in solvents are used to calculate diffusion coefficients for the penetrant at 25°C. Diffusion coefficients for constant diffusion and concentration‐dependent diffusion are obtained from Fick's law in a manner similar to that employed by Crank. For concentration‐dependent diffusion, solutions of solvent and nonsolvent in various proportions (cyclohexane and acetone for butyl vulcanizates) was employed. Although it is known that some of the nonsolvent is sorbed by the polymer from the solvent‐nonsolvent solution, the method still is applicable, in form, for determination of the diffusion coefficient of the solvent at zero solvent concentration. The sorption of liquid by the elastomer is shown to be a rather sharp advancing front, with the concentration of penetrant at the center of the sample remaining nearly zero until equilibrium is approached. This behavior is a direct consequence of the exponential dependence of diffusion on concentration.
Dipole moments and molecular structure of copolymers. I. Dipole moment of methyl methacrylate–styrene copolymers
Authors: Shima Mikiko 
Published: April 2003

AbstractThe dielectric properties of methyl methacrylate–styrene copolymers in benzene solution have been measured, and in a theoretical treatment it has been attempted to evaluate the effective dipole moment of the methyl methacrylate group in relation to the distribution of polar group sequences in the copolymer molecule. If it is assumed that the polar groups in a polar (A)–nonpolar (B) copolymer molecule can be classified into three types such that the nearest neighbors along the chain are (I) two polar groups A, (II) a polar group A and a nonpolar group B, and (III) two nonpolar groups B (the molecular polarizations of which are denoted by PAA, PAB, and PBB, respectively), then the average molecular polarization of polar group A in the copolymer molecule, Pav, can be written in the form

Here fAA and fAA2 are the probabilities of an AA sequence and a double AA sequence arising in the copolymer molecule, respectively. The values of fAA and fAA2 can be calculated from the reactivity ratios of the two monomers and the composition of the initial monomer mixture. The measurements were made on six samples of different compositions. It has been shown that the experimental values of Pav agreed satisfactorily with the values calculated from the above equation, over the whole range of copolymer composition. This seems to indicate that only the nearest neighbors in the polymer chain affect the effective dipole moment of the polar group in the copolymer molecule.
The calculation of the number‐average degree of polymerization starting from intrinsic viscosity and overall rate
Authors: Henrici‐Olivé G. , Olivé S. , Schulz G. V. 
Published: April 2003

AbstractThe relation between the intrinsic viscosity [η] and the number‐average degree of polymerization P̄n is a function of the molecular weight distribution of the polymer. In a polymer in which the termination of polymer radicals occurs partly by combination of two growing chains, this molecular weight distribution depends on number and extent of additional reactions such as chain transfer; i.e., it is variable. Therefore P̄n of such polymers cannot be obtained from intrinsic viscosity measurements by means of an equation of the type [η] = KP̄na.A new method is proposed which allows the evaluation of P̄n in these cases, without necessity of osmotic (or related) measurements or fractionation. The viscosity‐average degree of polymerization P̄η, which can be obtained exactly by experiment, is related to the number average by P̄η = P̄n(1 + F). Here F is given as a function of experimental data: P̄η and the overall rate of polymerization. This function is represented in a graph which enables the exact determination of P̄n without knowledge of number and extent of additional reactions.The P̄n values calculated according to the proposed method are compared with measured values (osmosis, endgroup analysis) for several polystyrene samples. The agreement is very satisfactory.
Dielectric dispersion of protein solutions in viscous solvent
Authors: Takashima Shiro 
Published: April 2003

AbstractThe dielectric dispersion of bovine hemoglobin, ovoalbumin, and bovine ferrimyoglobin was investigated in a glycerin‐water mixture. It was found that the dispersions, of these protein solutions were largely modified by the increase of the viscosity of the solvent and a linear relationship was obtained between the relaxation times and the viscosity of the solvent postulated by the Stokes law. On the contrary, the dispersion of catalase solution was not affected by the addition of the glycerin, which indicated that the dielectric polarization of this protein was due to the different polarization mechanism and the polarization by surface ion conduction was suggested.
Heats of polymeric reactions. Part I. Construction of the calorimeter and measurements on some new monomers
Authors: Joshi R. M. 
Published: April 2003

AbstractA modified isothermal distillation calorimeter is described in which an electronic weight recording device has been incorporated. Heats of polymerization of four vinyl monomers have been verified and −ΔHp values at 74.5°C. for six new monomers are reported. The values for acrylamide and methacrylamide furnish some evidence of association in the monomeric state in nonpolar solvents.
Kinetics of block polymerizations
Authors: Brepoels J. , Smets G. 
Published: April 2003

AbstractThe chain decomposition of tert‐butyl hydroperoxide in the presence of copperoctoate producestert‐butoxide and tert‐butyl peroxy radicals which are both able to initiate the polymerization of styrene. Consequently, half the number of the endgroups of the polymer molecules will be present, as peroxybutyl group, which can initiate a second‐step polymerization. In the first part of this paper, the kinetics of polymerization of styrene with t‐butyl hydroperoxide (t‐BHP) and copper octoate have been studied. In the absence of monomer, the chain decomposition is relatively short on account of the reaction of the Cu1+ ion with tert‐butyloxide radical and the precipitation of the copper salt; contrarily, in the presence of styrene the primary radicals add preferentially monomer, and no copper salt precipitation occurs. In both cases the overall energy of activation of decomposition t‐BHP/Cu2+ octoate is equal to above 21 kcal/mole. At constant Cu(oct)2 concentrations the square root law relationship between the rate of polymerization and t‐BHP concentration is only valid for the low concentrations; at higher values, it increases much slower up to an asymptotic value. Similar conclusions arise from the rate dependence on the copper octoate concentrations at constant t‐BHP and monomer concentrations.In the second part of this paper, the polystyrene carrying peroxy‐t‐butyl end‐groups has been used as initiator of the polymerization of a second monomer (methyl methacrylate and vinyl acetate) for the synthesis of block polymers at 97°C. This second step polymerization is a first order reaction with respect to the monomer concentration, and 0.5 order with respect to the initiator. Some thermal polymerization of methyl methacrylate must be taken into account for the evaluation of the amounts of second homopolymer. The relative reactivity of both radicals has been evaluated from their ability of further monomer addition; by measuring the amounts of homopolymer RH and block polymer RB by fractional precipitation and determination of their styrene content, it was possible to determine the efficiency of block polymerization.In the case of methyl methacrylate the ratio RB/RH is equal to 1.2 in agreement with the chain termination reaction; therefore the efficiency of both radicals is admitted to be equal, and consequently independent of their size.In the case of vinyl acetate the much lower value of RB/RH (0.26) is not a measure of the relative efficiency but a consequence of chain transfer reactions on monomer and solvent, which increase the amount of homopolymer.
On the characterization of stereoregular polymers. III. Polymethyl methacrylate
Authors: Miller Robert L. 
Published: April 2003

AbstractThe tacticity theory previously reported was generalized so it could be applied to the proton magnetic resonance data obtained for a variety of methyl methacrylate polymers. This system is the only one known for which sufficient data exist or may be obtained to provide a test of the theory. From the data available, parameters characterizing the distribution of iso‐ and syndiotactic sequence lengths in each sample were obtained These parameters, in turn, were used to predict melting behavior for each sample capable of crystallization. The tacticity theory not only is consistent with the data on free radical‐initiated (syndiotactic) polymers, about which there was no question of interpretation, it also provides an explanation for an uncertainty in the interpretation of the data on anionic‐initiated (isotactic) polymers. Thus, in this case at least, the theory appears to provide a connection between experimentation and polymer configuration.
The thermal degradation of some epoxy resins
Authors: Neǐman M. B. , Kovarskaya B. M. , Golubenkova L. I. , Strizhkova A. S. , Levantovskaya I. I. , Akutin M. S. 
Published: April 2003

AbstractThe thermal degradation of epoxy resins was studied in a static system over the temperature range 300–450°C. The reaction proceeds without an induction period, the initial rate being maximum. The rate W increases with temperature according to the law W = Ae–E/RT. The effective activation energy was 35 kcal./mole. The reaction products consist of gases, a resinous liquid, and a solid residue. The liquid has practically the same spectral characteristics in the infrared as the initial epoxy compound. In the infrared spectrum of the residue the bands characteristic of the epoxy group are absent. Water and formaldehyde were found among the liquid products. Methane and carbon monoxide were found in large amounts by means of a chromatographic method. In the thermal degradation of the unhardened epoxy resin the low molecular fraction volatilizes, and the high molecular fraction degrades liberating the radical which isomerizes and decomposes to CO and ĊH3. The methyl radical abstracts a hydrogen atom from the polymer and is converted to methane. The ROĊH2 radical formed on liberation of the epoxy group yields formaldehyde. Among the gaseous products formed in the thermal degradation of the epoxy resin hardened by polyethylene polyamine (PEPA) were found H2, CO, CH4, C2H6, C2H4, C3H6, and C3H8. Ethane, ethylene, propylene, and propane are possibly produced by decomposition of the PEPA radical. The thermooxidative degradation of epoxy resins was investigated in a static system. The reaction was shown to be of the degenerate branching chain type. The dependence of the induction period on the oxygen pressure and on the temperature was determined.
Copolymerization with Ziegler‐Natta catalysts. Part I. Monomer reactivity ratios for two α‐olefin pairs
Authors: Anderson I. H. , Burnett G. M. , Tait P. J. T. 
Published: April 2003

AbstractCrystalline copolymers of styrene and 4‐methylpent‐1‐ene and styrene and 5‐methylhex‐1‐ene have been prepared with the catalytic system α‐TiCl3–AlEt3 in toluene. The polymerizations were carried out in dilatometers with the use of a special stirring apparatus which is described. The copolymers produced were shown to be heterogeneous in composition. Fractions soluble in cold pentane are enriched in 5‐methylhex‐1‐ene and have x‐ray diffraction patterns similar to those of crystalline isotactic poly(5‐methylhex‐1‐ene). The fractions insoluble in cold pentane are enriched in styrene and on crystallization have x‐ray diffraction patterns similar to those of crystalline isotactic polystyrene. Infrared spectra were also examined. Determination of reactivity ratios gave the values: styrene (M)‐4‐methylpent‐1‐ene, r1 = 0.89 ± 0.05, r2 = 3.67 ± 0.22; styrene (M)‐5‐methylhex‐1‐ene, r1 = 0.59 ± 0.057, r2 = 4.00 ± 0.28. Statistical analysis shows that the copolymer is probably a mixture of block macromolecules, the chain backbones consisting mainly of one monomer type with short blocks of the other.
Synthesis of new monomers and polymers. II. 3‐methyl‐5‐isopropenylpyrazoles and derivatives
Authors: Dufonteny L. , Mifuna E. , Neirynck G. , Teyssié Ph. 
Published: April 2003

AbstractThe synthesis of 3‐methyl‐5‐isopropenylpyrazole and 1‐phenyl‐3‐methyl‐5‐isopropenylpyrazole is described, as well as the isolation of an addition compound with vinyl isocyanate, namely the N‐vinyl‐1‐(3‐methyl‐5‐isopropenylpyrazolyl)carboxamide. The 3‐methyl‐5‐isopropenylpyrazole only is able to homopolymerize, giving a characteristic polyelectrolyte, but both pyrazoles copolymerize readily with acrylic acid to yield polyampholytes. The addition compound, whose structure is proved by several methods, polymerizes readily; the soluble product obtained may undergo a grafting reaction with other monomers, but the polymer obtained is highly crosslinked.
Anionic polymerization of acrylonitrile by cyclopentadienyl sodium
Authors: Zilkha Albert , Ottolenghi Ariel 
Published: April 2003

AbstractThe anionic polymerization of acrylonitrile by cyclopentadienyl sodium in tetrahydrofuran was studied. The effects of the concentration of monomer, catalyst, temperature, and added cyclopentadiene on the polymerization were investigated. Contrary to previously studied anionic polymerizations, the molecular weight was found to increase with monomer concentration as a result of the cyclopentadiene radical acting as a polyfunctional catalyst due to the following equilibrium:
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The cyclopentadienyl polymer anions thus formed (which have 5 resonance structures) initiate polymerization especially at high monomer concentration leading to increase in molecular weight as a result of the formation of several polymeric chains attached to the same cyclopentadienyl radical. Proof for the existence of such polymers was obtained on treatment of the polymers with ozone which caused considerable lowering of the molecular weight due to scission of polymer side chains as a result of the opening of the cyclopentadiene rings. X‐ray diffraction diagrams of the branched polymers showed no strong reflection band at 5.3 A. which is associated with hydrogen bonding between chains of polyacrylonitrile. The molecular weight was independent of catalyst concentration and increased with lowering in temperature. Polymerization in the presence of free cyclopentadiene led to lowering in molecular weight due to termination by the acidic hydrogen of cyclopentadiene; plot of molecular weight against the reciprocal of the cyclopentadiene concentration gave a straight line. The polyacrylonitriles, having cyclopentadiene end groups, were utilized to introduce different end groups by the Diels Alder Reaction with dienophiles. Thus the adduct of the polymer with maleic anhydride gave an amide on reaction with amine.