bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of crystallization of isotactic polypropylene between 120 and 160°C.
Authors: Marker Leon , Hay Peter M. , Tilley George P. , Early Robert M. , Sweeting Orville J. 
Published: April 2003

AbstractPhysical changes which accompany the crystallization of isotactic polypropylenes have been observed by dilatometry and optical microscopy at temperatures between 120 and 160°C. Samples were fused at 220°C. and then held at a predetermined crystallization temperature for times ranging up to many hours. Rate constants for the crystallization were calculated from volume changes and from measurements of radial growth of spherulites. Polypropylenes from different sources exhibited quite different concentrations of spherulites and growth rates. Crystallization appears to proceed, at least at the higher temperatures, by spherical growth from a fixed number of nuclei, apparently arising from foreign matter in the polymer. With decreasing temperature, the number of nuclei (hence also the number of spherulites) increases, since apparently the conditions for nucleation become less critical. The crystallization follows the kinetics of a nucleation‐controlled process according to an Avrami equation, ‐log (1 ‐ ΔV / ΔV ∞) = kt3. Deviations from the third power of time at the lower temperatures may be the result of a secondary ordering process, slower than the primary crystallization.
Polymerization of vinyl bromide in solution
Authors: Blauer G. , Shenblat M. , Katchalsky A. 
Published: April 2003

AbstractThe polymerization of vinyl bromide in 1,2‐dibromoethane solution has been investigated using 2,2′‐azobisisobutyronitrile as thermal initiator. Rates of polymerization were followed in high vacuum by dilatometric and gravimetric measurements. Under the conditions employed, the polymerization showed no acceleration of rate. Up to about 12 hours reaction there was no significant loss of bromine from the polymer. At 35°C. and in the monomer concentration range 1–5 M, the initial rate was dependent on a power close to 2 of the monomer concentration. The rate at 35°C. was also dependent on a power close to 1.0 of the initiator concentration in the range 0.01–0.1 M. Styrene yielded an exponent 0.5 for the initiator at analogous experimental conditions. The average molecular weight of the initial polymers prepared under the conditions and in the concentration ranges indicated above were determined by light scattering and viscometry. The molecular weights were of the order of 100,000 and did not depend significantly on the initiator concentration. The intrinsic viscosities increased by only 50% when the monomer concentration was increased threefold and showed even less variation when the reaction temperature was lowered to 20°C. It is suggested that the polymerization system, though in apparent homogeneous solution, is close to phaseseparation, and beyond a critical range of degree of polymerization the highly coiled macromolecular radicals are unable to terminate by bimolecular collision, while at still higher degrees, even propagation inside the buried radicals ceases. This mechanism is supported by temperature dependent reversible association phenomena found previously. Alternative explanations based on chain transfer reactions involving unreactive radicals are discussed.
Nitrogen‐containing monomers. I. Copolymerization reactions of N‐alkyl maleamic acids and N‐alkyl maleimides
Authors: Coleman L. E. , Conrady J. A. 
Published: April 2003

AbstractThe polymerization reactions of some N‐alkyl maleamic acids and N‐alkyl maleimides have been described and a number of copolymers have been characterized. The N‐alkyl maleamic acids do not homopolymerize under the conditions employed but do copolymerize with styrene, acrylonitrile, and methacrylates. N‐Alkyl maleimides form homopolymers readily and copolymerize with a variety of vinyl monomers. Reactivity ratios of N‐butyl maleimide with styrene and methyl methacrylate have been determined, and Q and e values have been calculated.
The spreading of liquids on polyethylene film. The effect of preprinting treatments
Authors: Allan A. J. G. 
Published: April 2003

AbstractA study has been made of the wettability of thin films of polyethylene by observing the equilibrium advancing contact angle formed by a drop of liquid on the surface. Treatment of polyethylene film by exposure to methane/oxygen flames of varying intensity produces a controllable increase in the polarity of the surface as measured by the contact angles with a series of solutions of ethyl alcohol in water. The surface tension lowering of water by ethyl alcohol required to give complete spreading was determined for each flaming condition and related to the adhesion of a polar printing ink. It is shown that an essential criterion for good ink adhesion is the complete wetting of the film surface by the ink. It is suggested that a simple measure of the efficacy of the preprinting treatment would be the contact angle of water with the film.
The effect of the alkyl group on the irradiation grafting of methyl methacrylate to poly(alkyl methacrylates)
Authors: Graham Roger K. , Gluckman Muriel S. , Kampf Mary J. 
Published: April 2003

AbstractGamma irradiation of methyl methacrylate monomer in the presence of crosslinked poly(methyl methacrylate) leads to essentially no incorporation of new polymer into the insoluble network. Irradiation of solutions of poly(alkyl methacrylates) in methyl methacrylate produces graft copolymers in relatively low efficiency when the alkyl group is butyl, lauryl, stearyl, isopropyl, 2‐ethylhexyl, cyclohexyl, or neopentyl, but little grafting is observed when the alkyl group is tert‐butyl. It is concluded that prediction of grafting efficiencies cannot be made from the relative energy requirements for polymerization of monomer and cleavage of main‐chain carbon‐carbon bonds in the polymer. Evidence for grafting of alkyl methacrylates to poly(alkyl acrylates) is also presented.
Polymerization of triallyl cyanurate‐polyester resins
Authors: German Dale E. , Clampitt Bert H. , Galli Joseph R. 
Published: April 2003

AbstractDifferential thermal analysis data and infrared spectra are utilized to establish the mechanism by which a particular triallyl cyanurate‐polyester (Vibrin 135) resin polymerizes. It is shown that approximately one‐fourth of the polyester double bonds are of the furnarate type and that only these are capable of homopolymerization. In Vibrin 135, however, all of the polyester double bonds polymerize, along with two of the triallyl cyanurate double bonds, giving rise to one exothermic peak. From the nature of this polymerization it is inferred that a substantial amount of copolymerization occurs. Polymerization of the final triallyl cyanurate double bond, along with isomerization to the polymerized triallyl isocyanurate form, gives rise to a second exothermic peak. Correlation of measured heats of polymerization and infrared data tends to substantiate the proposed mechanism.
Linear phenol‐formaldehyde polymers: Synthesis of ortho‐para linked polymers
Authors: Burke W. J. , Ruetman S. H. , Higginbottom H. P. 
Published: April 2003

AbstractLinear ortho‐para linked phenol‐formaldehyde polymers were prepared by the addition of tetrahydrofuran solutions of o‐chlorophenol‐formaldehyde polymers to liquid ammonia containing sodium. The resulting phenol‐formaldehyde polymers were crosslinked much more slowly by reaction with hexamethylenetetramine than were the isomeric ortho‐ortho linked phenol‐formaldehyde polymers. Infrared and acetylation studies were consistent with proposed structure.
cis‐trans Isomerization in polyisoprenes. Part III. Reduction in the rate of crystallization of natural rubber at low temperatures by treatment with sulfur dioxide
Authors: Cunneen J. I. , Watson W. F. 
Published: April 2003

AbstractThe explanation given previously for the low rates of crystallization of natural rubber at moderately low temperatures after treatment by thiol acids leads to the prediction that treatment of rubber with sulfur dioxide above the ceiling temperature will give modified rubbers of low crystallization rates. This prediction is confirmed. Butadiene sulfone addition to rubber and heating to a convenient rate of its decomposition also gives rubber of low rate of crystallization. The cis‐trans mechanism of reaction is briefly discussed.
Wettability of perfluorocarbon polymer films: Effect of roughness
Authors: Allan A. J. G. , Roberts R. 
Published: April 2003

AbstractThe wettability of various perfluorocarbon polymer surfaces has been studied by observing the advancing and receding contact angles formed by a drop of liquid on the surface. Differences in hysteresis can be given a reasonable interpretation in terms of surface topography. The variation in roughness changes the advancing contact angle by as much as 30° and the advancing‐receding hysteresis varies from 13–59°. It is suggested that the receding angle is probably the more important in adhesion of ice where drops are blown across the surface at glancing angles and, therefore, exceedingly smooth perfluorocarbon polymer surfaces may be better than rougher surfaces for this application. No significant difference was observed between the two polymer structures, polytetrafluoroethylene and the copolymer of tetrafluoroethylene and hexafluoropropylene.
Electron exchange polymers. XI. Oxidation potentials and spectra of water‐soluble hydroquinones and polymeric hydroquinones
Authors: Robinson Ian D. , Fernandez‐Rofojo M. , Cassidy Harold G. 
Published: April 2003

AbstractReproducible potentiometric titrations of water soluble electron exchange polymers have been obtained. Sulfonated polyvinylhydroquinone homopolymers and a sulfonated copolymer of vinylhydroquinone with α‐methylstyrene were prepared by treatment of the corresponding dibenzoates with concentrated sulfuric acid. Oxidative titrations with ceric sulfate and bromine water are described. It was found that the apparent standard oxidation potential depends on the degree of reduction and is independent of molecular weight, for large molecular weight. These experimental facts are in agreement with a recent theoretical analysis. The standard oxidation (midpoint) potentials of the polymers are somewhat higher than similarly treated isopropylhydroquinone dibenzoate, model monomer. Some effects of salt and pH on the polymer titration behavior are described. Although the polymer potentials are established slowly on platinum electrodes, ultraviolet absorption studies have shown that the oxidation reaction itself is rapid. A pink‐colored intermediate was observed. The effects of sulfonation of two hydroquinones on their oxidation potentials and ultraviolet absorption spectra are described.
Chain transfer to a mixture of agents: The anomalous behavior of the acrylonitrile–dimethylformamide–water system
Authors: Jenkins A. D. , Johnston R. 
Published: April 2003

AbstractA method is described for determining the velocity constant for chain transfer in a vinyl polymerization to a relatively weak transfer agent which occupies a significant volume fraction of the reaction mixture. The method is particularly useful for cases in which precipitation of the polymer by the transfer agent would occur in the absence of an additional solvent. Some results for the acrylonitrile–dimethylformamide–water system are given, and the observed anomalous chain transfer behavior is interpreted in terms of the formation of a hydrate of dimethylformamide which is believed to be inert with respect to growing acrylonitrile radicals.
The optical behavior of spherulites in crystalline polymers. Part I. Calculation of theoretical extinction patterns in spherulites with twisting crystalline orientation
Authors: Keith H. D. , Padden F. J. 
Published: April 2003

AbstractThe extinction behavior of spherulites in many polymers and nonpolymers is shown to result from a characteristic twisting of crystal orientation acquired during growth. Extinction patterns are calculated for model spherulites consisting of radial fibers in which uniaxial or biaxial crystalline fibers twist regularly in a right‐ or left‐handed sense about the fiber axis. The results are in good agreement with observed extinction patterns in all of the following cases: diametral sections of three‐dimensional spherulites, diametral sections tilted on a Federow universal stage, and two‐dimensional spherulites grown in thin films. Details of this correlation will be given in Part II. Rules are given for (a) detecting the existence of twisting orientation, (b) determining whether it is of right‐ or left‐handed sense, and (c) determining the crystallographic axis about which twisting occurs.
On extinction patterns of polymer spherulites
Authors: Price Fraser P. 
Published: April 2003

AbstractThe extinction patterns between crossed nicols shown by two types of arrays of uniaxial crystals have been investigated. The arrays were (a) a disk whose radii were twisted arrangements of such crystallites, the plane of the disk being tilted at an arbitrary angle to the direction of observation, and (b) a cone of arbitrary apex angle whose sides were composed of twisted arrangements of crystallites, the cone being observed along the axis. The optic axes of the crystallites make an arbitrary but fixed angle with a radius of the disk or a ray of the cone. The extinction patterns of the disks can be circles, distorted displaced loops or zigzags, or mixtures of these, depending on the parameters. The extinction patterns of the conical arrays can be spirals or zigzags or both.
Kinetics of the Alfin polymerization of styrene and isoprene
Authors: Cleland Robert L. , Letsinger Robert L. , Magat Eugene E. , Stockmayer W. H. 
Published: April 2003

AbstractThe overall rate of polymerization of styrene and isoprene with the heterogeneous allylsodium–sodium isopropoxide–sodium chloride (Alfin PP) system as initiator is reaction‐controlled and is first order with respect to monomer and proportional to the amount of initiator present. The intrinsic viscosity of the product is independent of the monomer and initiator concentrations. The rate of styrene polymerization is independent of alkoxide concentration over a certain range, while the intrinsic viscosity increases with increasing alkoxide concentration. The activation energy of the overall rate is about 12 kcal./mole for styrene and 10 kcal./mole for isoprene. The simplest explanation of the kinetic results assumes initiation and termination steps involving the monomer. The distribution of molecular weights in Alfin polystyrene appears very broad. The kinetic features of this reaction bear a strong resemblance to those of the formation of isotactic polymers from the alkyl aluminum–titanium chloride system (Ziegler catalyst.)
Infrared spectra of crystalline polysaccharides. II. Native celluloses in the region from 640 to 1700 cm.−1
Authors: Liang C. Y. , Marchessault R. H. 
Published: April 2003

AbstractThe infrared spectrum of uniplanarly oriented valonia cellulose film and the polarized infrared spectra of doubly oriented films of ramie and bacterial cellulose crystallites have been observed in the region from 640 to 1700 cm.−1. The spectra have been interpreted with the assistance of band assignments in cellulose derivatives and related small molecules. Data obtained from deuterated material, band polarizations, and tilting effects have also been used. The perpendicular band at 1317 cm.−1 is assigned to the CH2 wagging mode. The highly parallel polarized band at 1162 cm.−1 is assigned to the antisymmetric bridge COC stretching frequency and the slightly parallel polarized band at 1110 cm.−1 is assigned to a ring stretching frequency. The interpretations of the other observed bands are discussed generally.
The polymerization of acrylonitrile in aqueous solution. Part I. The reaction catalyzed by Fenton's reagent at 25°C.
Authors: Dainton F. S. , Seaman P. H. 
Published: April 2003

AbstractAn apparatus is described for following dilatometrically the polymerization of acrylonitrile in aqueous solution initiated by ferrous salts and hydrogen peroxide. A steady rate (Rp) is rapidly established which ultimately decreases rapidly but does not fall to zero after the initiator is consumed. From measurements of the concentration of the ferrous ion surviving the reaction, the effect of cupric, fluoride, and ferric ions on this, on Rp, on the final phases of this reaction, and on the corresponding reaction with methyl methacrylate, it is concluded that polyacrylonitrile radicals are oxidatively terminated by cupric and ferric ions, but polymethyl methacrylate radicals are not. When this linear termination is suppressed, Rp is proportional to [m1]2 at low monomer concentrations and linearly dependent on [m1] at high concentrations. The transition from one state of affairs to the other occurs at a monomer concentration which first decreases and then increases as the initiation rate (Ri) increases. These results are believed to be general for all modes of initiation and include all previous data, reconciling conflicting information. A qualitative interpretation of these results is given in terms of the fairly rapid attainment of a constant number of polymer particles on which monomer is weakly adsorbed, a proportion of which are at any given moment inert, the remainder growing by consuming adsorbed monomer. Initiation, propagation, and mutual termination in the aqueous phase all play a significant part.
The polymerization of acrylonitrile in aqueous solution. Part II. The reaction photosensitized by Fe3+, Fe3+OH−, Fe2+, and I− ions
Authors: Dainton F. S. , James D. G. L. 
Published: April 2003

AbstractThe polymerization of acrylonitrile in aqueous solution photosensitized by Fe2+, Fe3+OH−, and I− has been determined dilatometrically at 25°C. After an acceleratory phase caused partly by increasing intensity of absorbed light due to light‐scattering by the insoluble polymer particles, a steady rate Rp is established and continues up to ∼10% conversion. Rp is proportional to Iabs[m1]1.0, where x is slightly greater than 0.5 unless ferric ions are present which may oxidize and terminate polyacrylonitrile radicals and cause x to be greater than 0.5. In accordance with earlier measurements, ϕ for the reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Fe}^{3 +} {\rm OH}- {{{3130\ {\rm A}.} \atop {-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-5pt\longrightarrow}}\atop{}}{\rm Fe}^{2 +} + {\rm OH}$$\end{document} is found to be 0.15. Propagation occurs by addition (a) of dissolved monomer molecules to polymer radicals S* (kp = 1.45 × 104 l. mole−1 sec.−1) and (b) of adsorbed monomer molecules to the radical in suspended polymer particles P* which contain several polymer molecules and one growing radical. S* radicals are subject to mutual termination (kt = 2 × 109 l. mole−1 sec.−1) and oxidative termination by ferric ion (k4 = 1.3 × 104 l. mole−1 sec.−1). As soon as the steady state is established [P*] is constant, but after stopping irradiation [P*] decays slowly and bimolecularly and therefore gives rise to a small aftereffect. Agitation causing the polymer suspension to coagulate (a) reduces Rp due to changes in Iabs and a decrease in the number of particles and (b) decreases the half‐life of the aftereffect by increasing the rate of mutual destruction of P* particles.
The polymerization of acrylonitrile in aqueous solution. Part III. The ferric ion‐photosensitized reaction at 15, 25, 30, and 50°C.
Authors: Dainton F. S. , Eaton R. S. 
Published: April 2003

AbstractThe Fe3+OH− photosensitized polymerization of acrylonitrile in aqueous solution at 15, 25, and 35°C. has been studied dilatometrically. Reproducible steady rates Rp, aftereffect rates Rpae, and stable fine polymer suspensions are observed. By the methods of kinetic analysis given in Part II, the following parameters of the reactions of S*‐type polyacrylonitrile radicals have been determined: propagation, Ap = 3 × 107 l. mole−1 sec.−1, Ep = 4.1 kcal. mole−1; mutual termination, At = 3.3 × 1013 l. mole−1 sec.−1, Et = 5.4 kcal. mole−1; termination by Fe3+OH−, Atf = 6.7 × 105 l. mole−1 sec.−1, Etf = 2.3 kcal. mole−1. Above 40°C. the polymer suspension precipitates more rapidly, Rp is less reproducible, and rate constants for the aqueous phase reaction cannot be determined. A system which has been photopolymerized at 25°C. when heated to 50°C. shows a short burst of reaction followed by an aftereffect which is smaller and decays more slowly than that which the system would have had at 25°C.
Stereoregulated polymerization in the free propagating species. I. Theory
Authors: Fordham J. W. L. 
Published: April 2003

AbstractThe theoretical aspects of a new method of regulating the steric structure in addition polymers are treated. The basic principle utilized is the directing force at the free end of the propagating species, as contrasted to the influence of a bound initiator. Only small differences in the free energies of activation of the isotactic and syndiotactic propagations are required for relatively significant changes in polymer structure, particularly at low polymerization temperatures. Both the relative amounts of the two configurations in the polymer and the distribution of individual sequence lengths bear a simple relationship to the two propagation constants. In the analogous rotational isomerism, the free energy difference between the gauche and trans conformations is known to be influenced by both steric and electrostatic factors. For molecules of the type ACH2CH2A, the difference in heat content is increased by an increase in the size or the polarity of the substituents and, for polar substituents, by a decrease in the dielectric constant of the medium. Steric and electrostatic factors at the free end of the growing polymer chain can, in theory, influence the structure in polymers. This conclusion is based on an estimate of steric and electrostatic energy components of the most probable conformational arrangements for the isotactic and syndiotactic configurations in representative polyvinyl chloride with theoretical structure. The refinement introduced by bond angle deformation can also be approximated for the two polymer configurations. With respect to each of the three energy components the syndiotactic configuration is the preferred structure, in agreement with known experimental results that polyvinyl chloride prepared under free radical conditions does contain syndiotactic sequences sufficiently long for x‐ray detection. The combined, alternate use of the directing force at the free end of the propagating species and that of a bound initiator to form syndiotactic–isotactic block copolymers is suggested.
Electrostatic interaction in dilute solutions of polyelectrolytes
Authors: Ise N. , Hosono M. 
Published: April 2003

AbstractInterionic interaction in dilute solutions of polyelectrolytes (the polymer‐concentration effect) has been discussed using an ionic distribution formula which Wicke and Eigen had proposed, introducing volume exclusion effects of the ions. Thermodynamic quantities, e.g., the activity coefficients, osmotic coefficient, and electric mobility are found to have a tendency to decrease with polymer concentration and to increase after passing through a minimum. A formulation of the “activity coefficient of macroions” has been obtained and is known to give a reasonable expression for the rate of change of the activity coefficient with the polymer concentration. The heat of dilution of polyelectrolyte solutions is shown to be positive in dilute solutions. Moreover, the treatment is extended to the titration behavior, and an interpretation is given for the characteristic run of viscosity‐concentration curves.