bluuebunny/crossref_metadata_2025_split huggingface dataset:
New features in polymer crystal growth from concentrated solutions
Authors: Bassett D. C. , Keller A. , Mitsuhashi S. 
Published: April 2003

AbstractThe three‐dimensional morphology of solution‐crystallized low pressure polyethylene has been examined for concentrations to 50% in xylene. Lamellar crystallization is characteristic of the whole range, and whenever diffraction examination has been possible, the lamellae have been shown to contain chain‐folded molecules. For crystallization from relatively dilute solutions (<0.3%) and below 75°C., earlier observations that the layers of multilayer crystals splay apart have been extended and the development of sheaving morphologies via the splaying of layers demonstrated. Sheaving has been interpreted as resulting from repulsion between portions of molecules excluded from the lamellar crystals. At higher concentrations and temperatures, molecules which crystallize through several lamellae become increasingly important. These are proposed as an explanation for a new, more compact, type of object which appears under the above conditions. They are designated axialites, as they consist of layers or layer packets splaying about a common axis (b). Viewed along this axis they appear sheaving, but as hexagons or fibrous ovals perpendicular to the axis. They thus resemble single crystals in some projections and incipient spherulites in others. Electron‐microscopic fine‐structure examination has shown that physical cohesion exists between the 100 A. terraces forming a layer packet on a 1000 A. scale. This is attributed to the interlamellar ties referred to above. This tying together of otherwise chain‐folded lamellae is considered as a plausible link between crystallization from dilute solution and from the melt. Disintegration and deformation of axialites has been studied in a preliminary way. Deformation has been found to consist of the relative displacement of otherwise intact layer packets. Some points concerning interlamellar connections and the possible relation between axialites and spherulites are also discussed.
Fundamental studies on cationic polymerization. III. Extension of mechanism studies to homogenous systems
Authors: Kirshenbaum I. , Kennedy J. P. , Thomas R. M. 
Published: April 2003

AbstractFundamental studies of the cationic polymerizations of isobutylene has been extended to the n‐pentane and carbon disulfide systems. The kinetic equation for the n‐pentane system is more complex than for other solvent systems because simplifying assumptions (which were possible for methyl chloride, ethyl chloride, and vinyl chloride) do not appear to be valid here. However, in all systems studied, the molecular weight of the polymer is determined principally by two competing chain breaking processes; namely, chain transfer from polymer to monomer and chain transfer or termination involving the solvent. The solvent reaction is important in polar solvents, especially at higher temperatures (e.g. −35°C.) but is much less important in either n‐pentane or carbon disulfide systems.
Study of the rate of heterogeneous polymerization of methyl acrylate in aqueous solution
Authors: Guha Tilak , Palit Santi R. 
Published: April 2003

AbstractStudy of the heterogeneous polymerization of methyl acrylate in dilute aqueous solution in a redox‐initiated system consisting in Na2S2O3K2S208 reveals the fact that the initial rate of polymerization increases with the increase in concentration of either of the redox pair. The rate, however, suffers a rapid deceleration in the course of polymerization in the region of high concentrations of the catalysts. At a low concentration of the initiators, addition of a small quantity of neutral electrolyte increases the rate, which falls off rapidly on further increase of the electrolyte concentration. Addition of emulsifiers in a concentration less than their critical micelle concentration inwater remarkably increases both the rate and the molecular weight. The rate of polymerization depends more or less linearly on monomer concentration when the concentration of the initiators is low in the medium. A monomer dependence tending to zero order is found when the catalyst concentration is high. Water‐soluble alcohols and glycols lower the rate when the insoluble phase in the heterogeneous polymerization is a stable colloid. Solvents such as dimethylformamide and benzene, which have strong affinity for the polymers produced in the medium, also reduce the rate. The peculiarities in the rate of this heterogeneous polymerization seem to be connected with the physical state of the insoluble polymer phase. The latter depends mainly on the ionic strength of the aqueous medium. At a low concentration of electrolytes, which may be either a neutral salt or water soluble electrolytic initiators such as K2S208/Na2S204, the insoluble phase is a stable colloid which changes via an unstable latex to a coarse precipitate on progressive increase of the electrolyte concentration in the medium. It appears that a kinetics similar to that of an emulsion polymerization operates when the insoluble phase is a stable colloid, suspension polymerization kinetics hold good when the insoluble phase is an unstable latex, and the kinetics of a typical “explosive” polymerization is the mechanism when the insoluble phase precipitates.
Grafting of poly (methyl methacrylate) to granular corn starch
Authors: Brockway C. E. , Moser K. B. 
Published: April 2003

AbstractGraft copolymers were prepared by the radical‐initiated polymerization of methyl methacrylate in aqueous slurries of granular corn starch. High conversions of monomer were realized, giving products which were readily recovered by filtration. The products were free‐flowing, white powders, which by microscopic examination looked much like granular starch. Grafting was demonstrated by extracting the granular products with ethylene dichloride, which in most instances removed only a minor part of the poly(methyl methacrylate). When azoisobutyronitrile was used for initiation, a high conversion of monomer resulted, but about 90% of the polymer was extractable with ethylene dichloride. Further evidence for grafting was obtained by extraction of predissolved product, prepared by dissolving the granular product in dimethyl sulfoxide, to destroy the structure of the starch granules, and precipitating with alcohol. The fractions soluble in ethylene dichloride contained significant amounts of carbohydrate. Similar treatment of product prepared with azoisobutyronitrile initiation or of physical blends of starch and poly(methyl methacrylate) gave much more efficient separation of starch from PMMA. Failure to obtain grafting with AIBN initiation suggests that grafting occurs mainly as a result of attack on starch by radicals generated by the reaction of hydrogen peroxide or organic hydroperoxide with ferrous iron. Acid hydrolysis of the products removed the starch. The PMMA so recovered typically had viscosity‐average molecular weights of the order of 106, which suggests the grafts contained very long branch chains of PMMA attached at very infrequent intervals.
Molecular weight distribution in polypropylene glycol 2025
Authors: Morris R. J. , Persinger H. E. 
Published: April 2003

AbstractThe new applications of polypropylene glycols as chemical intermediates, particularly in the polyurethane field, have shifted emphasis from purely physical properties, such as density, viscosity, and volatility, to chemical properties, such as hydroxyl content, unsaturation, and molecular weight: Because much interest is also being shown in the uniformity of chain length, i.e., the “molecular purity” of the polypropylene glycol, methods were investigated for measuring this property. A liquid chromatographic procedure has been developed which will yield molecular weight distributions for polypropylene glycols in the 2025 number‐average molecular weight range. The results approximate, but do not match, the values obtained by theoretical calculations. Details of the method and a typical distribution curve are presented.
Homopolymerization of maleic anhydride. I. Preparation of the polymer
Authors: Lang John L. , Pavelich W. A. , Clarey H. D. 
Published: April 2003

AbstractMaleic anhydride has been homopolymerized, contrary to accepted beliefs. Polymerization of either molten or dissolved monomer was initiated with the use of gammaradiation and free‐radical initiators. An anhydride having [η] = 0.146 dl./g. in acetophenone had a molecular weight of 23,100 (free acid), DP = 199, by the light‐scattering method. The carboxyl group propinquity is responsible for peculiar behavior of aqueous solutions of salts of the poly‐acid.
Polyethylene terephthalate structural studies
Authors: Schmidt P. G. 
Published: April 2003

AbstractThe absorption intensity of a given infrared absorption band, in the infrared spectrum of an oriented polymer is composed of an orientation and a structural factor. A method is discussed, using polarized infrared radiation, which will measure the contribution of each. The ethylene glycol linkage of the polyethylene terephthalate molecule may exist in either of two forms. These forms are rotational isomers. The trans form of the molecule is the extended form, the gauche form is the relaxed form. The amorphous regions of polyethylene terephthalate films have been found to contain both of these isomers. Polymer orientation is summarized in terms of transition moment types. Orientation parameters characteristic of polyethylene terephthalate films are defined.
Molecular orbital theory of reactivity in radical polymerization. Part III
Authors: Hayashi K. , Yonezawa T. , Okamura S. , Fukui K. 
Published: April 2003

AbstractThe chemical reactivity in diene type polymerization and degradative chain transfer is discussed by the theory previously proposed by the present authors. In addition to this, a molecular orbital procedure to calculate Q and e values is presented. Further, the stabilization energy and the reactivity ratios in various copolymerizations are calculated. The results coincide with experiment satisfactorily.
Studies on biocolloids and polyelectrolytes—the plant—gums viscosity of azrechtic acid
Authors: Kulshrestha V. K. 
Published: April 2003

AbstractAzrechtic acid (ARA) has been obtained by the electrodialysis of an aqueous solution of the gum of Azadirechta indica in an acidic medium. The viscosity of this gum acid has been investigated under different experimental conditions, i.e., with dilution in aqueous and in isoionic concentration of added electrolyte (HCl), and with change in pH. It is observed that the reduced viscosity of the aqueous solutions increases rapidly with dilution and the reduced viscosity—concentration curve is concave upwards instead of being linear as in the case of linear polymers. The viscosity of aqueous ARS solutions follows the equation, ηsp/C = A/(1 + B√C) where A, B, and D are constants (A = 0.03, B = 0.1845, and D = 0.05), as well as the equation ηsp/C = aCb, in which a and b are constants and equal to 0.2113 and −0.4375, respectively. It is observed that in isoionic concentrations of added electrolyte (HCl, 2.20 × 10−4 g.‐equiv./l.), the sharp rise in the ηsp/C versus C curve vanishes, and the curves show well defined maxima which shift to higher concentrations of the gum acid as the electrolyte concentration increases and ultimately vanish at sufficiently high concentration of the added electrolyte (HCl, 2.20 × 10−3 g.‐equiv./l.), and the ηsp/C versus C curves become linear. The viscosity of azrechtic acid at constant solute concentration increases rapidly when the pH is increased by the addition of NaOH, becomes maximum at a pH of about 6, after which it falls rapidly and becomes constant after a pH of 12. The viscosity also decreases when the pH is decreased on addition of HCl and becomes constant after a pH of 2.0. All these phenomena have been explained on the basis that azrechtic acid behaves as a polyelectrolyte.
Differential thermal analysis of high polymers. VI. Comments on some material and experimental factors
Authors: Ke Bacon 
Published: April 2003

AbstractSome factors in the differential thermal analysis (DTA) of high polymers were studied. A newly designed, small cell assembly was used in most of the work. The thermal history and, to a lesser extent, the molecular weight affect the size and shape of the thermogram, depending on the amount of crystallinity and the distribution of crystallite sizes in the polymer. Interference due to oxidation should be prevented in the characterization of a thermally unstable polymer. Large sample quantity may lead to multiple peaks in the thermogram. High heating rates result in more intense peaks but also shift peak positions. Thermogram profiles become distorted when the temperaturesensing thermocouple is placed in the sample.
Preparation and properties of copolymers of maleic anhydride and 2,2‐dimethylaminoethyl methacrylate
Authors: Taylor W. D. , Woodward A. E. 
Published: April 2003

AbstractPreparation of copolymers by reaction of N,N‐dimethylaminoethyl methacrylate with maleic anhydride in an excess of the latter and the presence of water is described. The reaction products have been characterized by elemental analysis, by conductiometric titrations with acid and with base, and by specific viscosity determinations and light‐scattering measurements in dilute solution. Although there is evidence that a 1:1 copolymer is formed, the results of the titrations and viscosity measurements indicate that this reaction product is a polyacid and not a polyampholyte. Light‐scattering measurements indicate that aggregation occurs in aqueous solutions of this polymer. Attempts to prepare regularly alternating polyampholytes from other monomer combinations are described.
Polymers derived from unsaturated esters of hydronopoxyalkanols
Authors: Shono Toshiyuki , Marvel C. S. 
Published: April 2003

AbstractHomopolymers of the acrylates of a series of hydronopoxyalkanols have been prepared and characterized as soft rubbery materials with some adhesive properties. The polymer from the methacrylate of hydronopoxyethanol was hard, brittle and insoluble. The crotonate of this alcohol did not homopolymerize was hard, brittle and insoluble. The crotonate of this alcohol did not homopolymerize in a free radical system. All of these esters copolymerized readily with vinyl chloride, styrene, acrylonitrile and butadiene. The vinyl chloride copolymers and styrene copolymers were rigid plastics. The butadiene copolymers were rubbery and easily crosslinked in air. The acrylonitrile copolymers were soluble in dimethylformamide. Terpolymers of these esters with butadiene and acrylonitrile were tough, rubbery compositions.
Polymerization and copolymerization of 1‐ and 9‐vinylanthracenes and 9‐vinylphenanthrene
Authors: Katz Dov 
Published: April 2003

AbstractThe free radical polymerization and copolymerization with styrene of 1‐ and 9‐vinylanthracenes and 9‐vinylphenanthrene was studied. The highest reactivity was shown by 9‐vinylphenanthrene and the lowest by 9‐vinylanthracene. From the experimental data on the copolymerization reactions the reactivity ratios r1 and r2 were calculated and for the two vinylanthracenes the values of Q2 (general reactivity) were obtained after application of the Price‐Alfrey scheme for correlating reactivities of vinyl compounds in copolymerization. The scheme was not used for 9‐vinylphenanthrene as the product of r1 × r2 was in this case greater than unity. It appears that the rates of polymerization (and copolymerization) of the three monomers are influenced by two factors: the steric hindrance to conjugation between the anthracene or phenanthrene system and the exocyclic double bond, and the nonaromatic character of the 9,10 double bond in phenanthrene. In 9‐vinylanthracene the conjugation between the anthracene system and the vinyl group is sterically more hindered that in the 1‐isomer, the resonance stabilization of the radical adduct of 1‐vinylanthracene is greater than in the case of the 9‐isomer and the latter is less reactive. In 9‐vinylphenanthrene and 1‐vinylanthracene the steric hindrance is the same and the higher reactivity of the first monomer as compared with the second seems to be due to the non‐aromatic character of the 9, 10 double bond in phenanthrene, which makes the 9‐vinylphenanthrene and almost aliphatic diene.
Transient analysis of a vibrating reed
Authors: Glauz R. D. 
Published: April 2003

AbstractA new simplified test for obtaining the physical properties of a viscoelastic material is described and analyzed. A reed, clamped at one end, is displaced at the free end and the damped oscillations measured. From measurements of the damping factor and frequency the complex modulus is computed. Tables of eigenvalues have been calculated for various masses and moments of inertia attached to the free end of the reed. Many experimental tests have shown the simplicity and usefulness of the method.
Self‐diffusion and nuclear relaxation in polyisobutylene
Authors: McCall David W. , Douglass Dean C. , Anderson Ernest W. 
Published: April 2003

AbstractVarious self‐diffusion and nuclear relaxation experiments are reported for a polyisobutylene of rather low molecular weight, in bulk and in solution. In the bulk, the self‐diffusion coefficient obeys the Arrhenius relation, yielding an activation energy of 5.5 kcal./mole. In solution the activation energies are lower, approaching the value for the solvent at low concentration. The self‐diffusion coefficient of the polymer at infinite dilution is 1.2 × 10−5 cm.2/sec. in CS2 and 0.44 × 10−5 cm.2/sec. in CCl4. The ratio is close to the inverse ratio of the solvent viscosities. Measurements of self‐diffusion of the solvent have been made for cyclohexane in polyisobutylene. A simple interpretation of the data in terms of Stokes‐Einstein models yields molecular dimensions which are too small by a factor of two or three.
Narrow molecular weight distribution polystyrenes
Authors: Brower F. M. , McCormick H. W. 
Published: April 2003

AbstractA study of the scope and limitations of the anionic polymerization of styrene and substituted styrenes under conditions in which a chain termination reaction is lacking was made. Under these conditions polymers of very narrow molecular weight distributions were obtained. Ultracentrifuge data are presented as evidence confirming the formation of narrow distributions. All reagents used were carefully purified and subsequently were not exposed to the atmosphere. Standard procedure was to conduct the polymerizations by adding monomer solution slowly to initiator solution. Deviations from this procedure were designed to study various reaction conditions. Monomers used were styrene, α‐methylstyrene, and m‐ and p‐vinyltoluene. Solvents used were tetrahydrofuran, tetrahydropyran, 2‐methyl‐tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. Initiators used were sodium–naphthalene, sodium–biphenyl, sodium–α‐methylstyrene, sodium–phenanthrene, and lithium–naphthalene. The choice of solvent had a great effect on the course of the polymerization and the temperature at which narrow distribution polymers could be produced. Solvents promoting rapid initiation and relatively slow propagation were best, and those promoting the reverse situation tended to give side reactions leading to termination and abroad distribution polymer. The order of promotion of rapid initiation and slow propagation for these solvents is dioxan > tetrahydrofuran > ethylene glycol dimethyl ether > diethylene glycol dimethyl ether. In dioxane solutions monodisperse polymer was prepared under a wide range of conditions. Monodisperse polymer could not be prepared under the most favorable conditions in diethylene glycol dimethyl ether. These effects were interpreted in terms of ion pair separation. Other factors which might lead to broad distribution polymers were examined. The age of the initiator was found to be very important, order initiator solutions giving broad distribution polymers. Aged initiator solutions were found to evolve hydrogen when allowed to react with water; freshly prepared initiator solutions evolved on hydrogen. In the presence of toluene there was chain transfer to the methyl group giving a broad distribution polymer. Similar transfer to benzene at the ring gave termination before polymerization was complete. Rusty iron, Fe2O3, and Fe3O4 adversely effected the course of polymerizations giving broad distribution polymers. Hydrogen‐reduced iron in the reaction mixture resulted in only minor deviation from narrow distribution.
Effect of solvents on the anionic polymerization of styrene by phenyllithium
Authors: Zilkha Albert , Barzakay Samuel , Ottolenghi Ariel 
Published: April 2003

AbstractThe anionic polymerization of styrene by phenyllithium was studied in various solvents The order of the decreasing molecular weights obtained depending on the solvent, was: tetrahydrofuran » toluene > benzene > petroleum ether > diethyl ether. The molecular weight, due to absence of termination, is governed by the ratio of the rate propagation to the rate of initiation (Rp/Ri). Both these rates are influenced by the dielectric constant and the solvating power of the solvent for the phenyllithium and for the growing end, solvation of the growing end being greater due to the resonance of the propagating styryl anions. This leads to the fact that on passing from petroleum ether (low dielectric constant) to tetrahydrofuran (relatively high dielectric constant and high solvating power), Rp increases much more than Ri, leading to higher molecular weight. The polymerization of styrene in mixtures of petroleum ether and tetrahydrofuran was studied by the addition of increasing amounts of tetrahydrofuran while keeping the catalyst and monomer concentrations constant. Initially (up to 2 vol.‐% tetrahydrofuran) there was a sharp decrease in molecular weight due to a greater dissociation of the phenyllithium, with a corresponding increase in Ri. On further addition of tetrahydrofuran (up to about 25 vol.‐%), the molecular weight increased and approached the order of that obtained in petroleum ether. This is due to a greater increase in Rp over Ri due to greater solvation of the propagating end. At this relatively high tetrahydrofuran concentration we have maximum solvation both of the catalyst and of the growing end. With further addition of tetrahydrofuran there is a linear dependence of the molecular weight both on the concentration of the tetrahydrofuran and on the dielectric constant of the system. Ether gave the lowest molecular weights, in spite of its relatively high dielectric constant, due to greater dissociation of the catalyst associates (C6H5Li)x leading to an increased efficiency of the catalyst (greater Ri). Toluene and benzene led to higher molecular weights than petroleum ether, although the dielectric constants are of approximately the same order, due to the homogeneous nature of the polymerization in these solvents as compared with the heterogeneous polymerization in petroleum ether. The molecular weight increased with decrease in temperature in various solvents due to the increase in the dielectric constant and the lowering in Ri
The reference point for liquid relaxation processes. II. Melt viscosity of polyisobutylene
Authors: Miller A. A. 
Published: April 2003

AbstractPublished (Fox and Flory) viscosity—temperature data for polyisobutylene are expressed by a modified Arrhenius equation: log η = log A + B′/(T ‐ T0). For higher molecular weight fractions (M > 2000) with estimated glass temperatures in the range Tg = −64 to −79°C., the derived reference temperature T0 is −150 (±10)°C., and B′ = 1240°. By comparison with Fox and Flory's empirical equations, the molecular weight dependency of the A parameter, below and above the “chain‐entanglement” point (M = 17000), is derived. The modified Arrhenius equation can also be expressed with WLF (Williams‐Landel‐Ferry) constants, where T0 = Tg − C and B′ = CC. The melt viscosity—temperature behavior is consistent with free−volume concepts if vf ⋍ (T − T0), as suggested by the Cohen‐Turnbull theory.