bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereospecific polymerization of α‐olefins with three‐component catalyst systems
Authors: Coover H. W. , Joyner F. B. 
Published: April 2003

AbstractIt is well known that mixtures of alkylaluminum dihalides and transition metal halides, such as titanium(III) chloride, are ineffective as catalysts for the stereospecific polymerization of α‐olefins. It has been discovered that the addition of a third compound, derived from one or more of the strongly complexing ligand elements such as nitrogen oxygen, and phosphorus, to such mixtures leads to catalysts having the highest stereospecificities known. In the present work, studies were made of the effect of various third components on the activity and stereospecificity of these catalysts in the polymerization of propylene. The stereospecificity and activity of three‐component catalysts of this type were dependent upon the ratio of the third component to the alkyaluminum dihalide. Optimum stereospecificity and activity were usually obtained at ratios in the range of 0.5–0.7. In general, catalytic activity increased with increasing basicity of the third component. Both stereospecificity and activity were influenced by the nature of the halogen atoms in the alkylaluminum dihalide, whereas the nature of the alkyl group affected only the activity, with the ethyl group providing the most active catalysts. The most stereospecific catalyst was made from a mixture of ethylaluminum diiodide, hexamethylphosphoric triamide, and violet titanium(III) chloride.
Solid‐state polymerization of trioxane
Authors: Rao H. , Ballantine D. S. 
Published: April 2003

AbstractTrioxane has been polymerized by irradiation with Co60 γ‐rays in the temperature range 45–55°C. The data are extremely difficult to reproduce in spite of great precautions in sample preparation. The reaction reaches a limiting conversion, generally about 40%, but conversions as high as 96% have been observed. The viscosity of the polymer decreases with increasing conversion. Post‐irradiation heating of monomer irradiated at low temperature (<30°C.) also leads to limiting conversions but much higher viscosity products. The polymerization has also been studied under pressure. Pressure applied to monomer prior to irradiation leads to higher conversions and higher viscosity polymers. In the post‐irradiation polymerization technique, application of pressure after irradiation reduces the polymer yield to zero in almost every instance.
Polymer production from aqueous solutions of D‐glucose by high‐energy radiation
Authors: Snell John B. 
Published: April 2003

AbstractPolymeric material was produced by passing aqueous glucose solutions under a beam of high energy electrons. The yield of polymer increased with dose and dose rate. The weight‐average molecular weights of polymers formed at 40 Mrad, measured by light scattering, ranged from 9,800 to 5,000,000. The polymers exhibited very low intrinsic viscosities in water, and are therefore though to be highly branched. Measurement of the number‐average molecular weight of one of the polymers by osmometry established an Mw/Mn ratio of 4.9, indicating a fairly broad distribution of molecular weights within the polymer. One polymer was fractionated on Sephadex and the chemical composition of the fractions compared. The carboxyl content increased regularly with molecular weight, suggesting that the carboxyl groups were the result of secondary oxidative attack. Hydrogen and oxygen contents decreased with increasing molecular weight. Elemental analysis and infrared spectral data on the fractions were consistent with the hypothesis that gluconolactone was incorporated into the polymer in the early stages of formation. Chromophoric groups, perhaps of the endiol type, were formed, and oxygen‐rich fragments were apparently lost as the molecular weight of the polymer increased. Oxygen contents, on the other hand, decreased with increasing molecular weight. The regularity observed in the fraction analyses suggested that the polymerization followed a pattern, and was not the result of the random joining of unlike fragments. Elemental analysis and infrared spectral data on the fractions were consistent with the hypothesis that gluconolactone was incorporated into the polymer in the early stages of formation. Chromophoric groups, perhaps of the enediol type, were formed, and oxygen‐rich fragments were apparently lost as the molecular weight of the polymer increased.
Chemical scission of poly(methyl acrylate)
Authors: Hwa Jesse C. H. , Miller Leon 
Published: April 2003

AbstractBy copolymerizing methyl acrylate with methyl α‐chloroacrylate at various ratios, the resulting poly(methyl acrylate) backbone had reactive chlorine sites. The poly(methyl acrylate‐co‐methyl α‐chloroacrylate) was dehydrochlorinated by amine. After hydrolysis to convert methyl ester to sodium salt of the acid, the unsaturated bonds introduced by dehydrochlorination were oxidized to glycol by potassium permanganate and cleaved by periodic acid. The resulting poly(sodium acrylate) was converted to the free acid by ion exchange and reesterified with diazomethane. Degraded fragments having number‐average molecular weights of 5,000–12,000 were obtained at 83% polymer recovery. Based on the original chlorine content, the efficiency of overall degradation was 20–26% and perhaps somewhat higher.
Polyphenylene‐s‐triazinyl ethers by interfacial polycondensation
Authors: Picklesimer Lewellyn G. , Saunders Thomas F. 
Published: April 2003

AbstractPolyphenylene–s‐triazinyl ethers of apparently high molecular weight have been prepared by the interfacial polycondensation of s‐triazinyl chlorides and sodium bisphenoxides. The polymers are characterized by good thermal stability, insolubility, and infusibility. The polymers can be varied by altering the reaction conditions. A long residence time at the reactive interface leads to a polymer of low residual chlorine and thus highly crosslinked. Reduction of the contact time at the reactive interface leads to polymers containing a greater amount of chlorine and consequently some linearity.
NMR study of polymers of ethyl, isopropyl, and tert‐butyl vinyl ethers
Authors: Ramey Kermit C. , Field Nathan D. , Borchert Alfred E. 
Published: April 2003

AbstractThe high resolution NMR spectra of poly(vinyl ethyl, isopropyl, isobutyl, and tert‐butyl ethers), yields, upon examination at 60 and 100 Mcycles/sec., and under the conditions of decoupling, information concerning the various tactic forms present. The spectra are complicated by the number of overlapping resonances to the extent that an unambiguous assignment of the three triad forms could not be made. For poly(vinyl isobutyl ether) the resonances of the α proton decoupled from the β protons exhibits three components which are tentatively assigned to the central monomer units in heterotactic, isotactic, and syndiotactic configurations, with increasing field strength, respectively.
Studies of variations in the properties of ion‐exchange resin particles
Authors: Freeman David H. , Patel Vithal C. , Smith Mary E. 
Published: April 2003

AbstractMeasurements of the swelling ratio and exchange capacity of individual ion‐exchange resin beads are used to compare resin samples, to study interparticle differences, and to help characterize resin degradation. Heterogeneous resin samples were found, along with those of apparent homogeneity. In one extreme case of the former, inert particle cores were found.
Flow behavior of polydimethylsiloxane
Authors: Kataoka Tadao , Ueda Shigeyuki 
Published: April 2003

AbstractViscosities of polydimethylsiloxane were measured over a wide range of shear rates and molecular weights to clarify the flow behavior of bulk polymers. It was observed that each flow curve for high molecular weight samples had an inflection point, and at high shear rates all curves tended to converge. The relationship between viscosities and molecular weights at various shear rates showed the following features: no sharp inflection in the zero shear relation and non‐Newtonian properties below Mc. It is suggested that viscosities of high molecular weight samples become almost the same, irrespective of molecular weight, at very high shear rates.
Thermostatted cell for a Brice‐Phoenix light‐scattering photometer
Authors: Smart C. 
Published: April 2003

AbstractA thermostat jacket is described for a Brice‐Phoenix light‐scattering photometer which allows accurate temperature control of the scattering medium over a wide range of temperatures. Modifications to the electronic system of the photometer have increased its sensitivity so that more accurate measurements can be made for low Rayleigh ratios. By using a circulating liquid of the same refractive index as the Pyrex glass cell, stray light within the cell has been reduced to a very low level. Some results for the Rayleigh ratios of water and benzene are presented.
A phenomenological theory of spherulitic crystallization: Primary and secondary crystallization processes
Authors: Price Fraser P. 
Published: April 2003

AbstractA theory is presented that takes into account the two stages occurring during the crystallization of bulk polymers. The theory assumes that all the crystallization occurs within the spherulites but that the amount of crystallinity at any particular point within a spherulite depends upon the age of that particular point. It is shown that these assumptions lead to transformation curves that look like those in actual polymer crystallizations.
Reaction of α, α‐diphenyl‐β‐picrylhydrazyl with acids
Authors: Solomon D. H. , Swift Jean D. 
Published: April 2003

AbstractThe action of dilute aqueous mineral acids on α,α‐diphenyl‐β‐picryl hydrazyl (DPPH) has been studied and shown to result in the rapid loss of the characteristic color of the radical. Hydrobromic and hydrochloric acids yield α,α‐diphenyl‐β‐picryl hydrazine (DPPH‐H) and the corresponding halogen‐substituted α,α‐diphenyl‐β‐picryl hydrazine. Hydroiodic acid gives DPPH‐H, iodine, and a small quantity of DPPH. A number of organic acids cause similar reactions. Kinetic studies on the hydrobromic acid system indicate that the reaction is first‐order with respect to: hydrogen ion concentration, DPPH concentration, and anion concentration. The ability of the anion to undergo one‐electron transfer and to dimerize are also important, and the strongest nucleophile gives the fastest reaction. A mechanism which involves ionic attack is proposed to account for the reaction of DPPH with acid. The limitations of DPPH in studying reaction mechanisms are then discussed in relation to the proposed ionic mechanism.
Average lifetime of growing chain in propylene polymerization
Authors: Tanaka Sanae , Morikawa Hiroyuki 
Published: April 2003

AbstractThe value of the active lifetime of the growing chain of propylene polymer obtained with TiCl3Al(C2H5)2Cl as catalyst was determined to be 33–40 min. by the method of calculating changes of number‐average molecular weight from measurements of molecular weight distribution. In addition, the influence of reaction conditions (reaction temperature, monomer concentration, catalyst concentration, reaction time, terminating agent) upon the active lifetime was examined. The data obtained support the theory of the occurrence of chain transfer. An expression was obtained for the lifetime distribution of the polymer.
Aliphatic poly‐1,3,4‐oxadiazoles
Authors: Unishi Terunobu , Hasegawa Masaki 
Published: April 2003

AbstractThree high molecular weight aliphatic polyoxadiazoles have been prepared by a new route from equimolar amounts of a diphenyl ester of dicarboxylic acid and an anhydrous hydrazine (or a dihydrazide). The resulting polymers have been characterized by microanalysis, intrinsic viscosity, x‐ray diffraction patterns, infrared absorption spectra, and by differential thermal analysis. Such polymers are soluble in several solvents and show very low melting temperature and high crystallinity.
Effects of rate of shear on the viscosity of polymer solutions
Authors: Fujishige Shoei 
Published: April 2003

AbstractViscosities of dilute solutions of poly(methyl methacrylate) in toluene and in chloroform were measured with a modified capillary viscometer. By tilting the viscometer one can control the solvent flow time to any desired condition, and by use of this technique it was possible to determine the extent to which such variables affect the resulting rate of shear if one measures the viscosities with two or more viscometers of the same type having different flow times of solvent. The reduced viscosities measured with the modified capillary viscometer at several tilting angles were plotted in the usual way against the polymer concentrations, and values of the intrinsic viscosity for a given solution at each tilting angle were thus obtained for both of the solutions studied. For a rather high molecular weight polymer fraction, the maximum variation in the molecular weight estimated from the intrinsic viscosity by the Mark‐Houwink relation was of the order of 20% between the values obtained with the viscometer fixed at a vertical and at another extreme angle. All the experimental data are also reproduced as a function of the rate of shear, and reliable values for the intrinsic viscosity at zero rate of shear and hence for the molecular weight are obtained. Other possible differences noted in the determination of such molecular characteristics as the Huggins′ constant which could be attributed to this kind of experimental condition were discussed.
Single crystals of amylose V complexes
Authors: Yamashita Yuhiko 
Published: April 2003

AbstractIn the present paper our previous results and Manley's results for single crystals of amylose V complexes are confirmed. A reasonable interpretation of electron diffraction patterns from lamellar crystals of the monohydrated complex and of the anhydrous complex is presented. It is concluded that the longer side of rectangular lamellae corresponds to the a axis of the unit cell of the wet complex, and that the crystal structure does not have hexagonal symmetry at the time when the lamellar crystals are formed in the supercooled solution. The mode of chain packing in the single crystals is described and discussed.
Carborane polymers. III. Vinyl carboranes
Authors: Green Joseph , Mayes Nathan , Cohen Murray S. 
Published: April 2003

AbstractIsopropenylcarborane could not be polymerized by conventional radical and ionic methods. A low molecular weight polymer of DP = 10 was obtained by the use of aluminum chloride as catalyst at 150–170°C. Carboranylmethyl acrylate was homopolymerized and copolymerized with fluoroacrylates by using benzoyl peroxide as catalyst. The Tg of the homopolymer was about 165°C. The difficulty in polymerizing the isopropenylcarborane and the high Tg value for carboranylmethyl acrylate polymer have been partially attributed to the steric requirements of the carborane group.
Energetic and entropic components of tension in elastomeric wool fibers
Authors: Haly A. R. 
Published: April 2003

AbstractTension against temperature data were obtained for both unreduced wool fibers and fibers in which some of the disulfide bonds had been reduced by a thiol. The measurements were done while the fibers contained a diluent. Coefficients of volume thermal expansion were also measured. From the results the ratio of the energetic component of tension to the total tension (fe/f) was calculated. Most values of fe/f were within the range ± 0.20. In the case of unreduced wool fe/f changed from negative to positive as the extension increased. With a reduced sample containing 8% of the native disulfide, fe/f was negative and nearly constant over the range of extension employed. The change for unreduced wool follows from extension‐dependent interactions between polypeptide chains. The results indicate that, for unperturbed polypeptide chains from wool taken into solution following disulfide reduction, the end‐to‐end distance will decrease with increase of temperature, a partially extended form being the lower energy state.
Preparation and properties of crystalline, low molecular weight poly(vinyl chloride)
Authors: Böckman Oluf Chr. 
Published: April 2003

AbstractThe preparation of low molecular weight (DP < 52) poly(vinyl chloride) by free radical solution polymerization in chain transfer agents, e.g., butyraldehyde, chloroform, tetrahydronaphthalene, and tetrahydrofuran, is described. It is found that such polymers are crystalline and that the degree of crystallinity increases with decreasing molecular weight.
Radiation crosslinking of nylon 66 and poly(vinyl alcohol)
Authors: Bernstein Bruce S. , Odian George , Orban Gyula , Tirelli Sebastian 
Published: April 2003

AbstractLow dose Co60 radiation of nylon 66 and poly(vinyl alcohol) in the presence of methanol–water–allyl methacrylate (AMA) mixtures allows crosslinking of the polymers. In both cases, crosslinking is facilitated by the presence of the polyfunctional monomer and does not occur in its absence. Nylon gel fractions of 40% have been obtained after a dose of 3 Mrad; poly(vinyl alcohol) gel fractions of over 75% have been obtained after 5 Mrad. With both polymers, the gel fraction is dependent upon the radiation dose, AMA level, and water level during radiation.
Probability of cyclopolymerization
Authors: Butler George B. , Raymond Maurice A. 
Published: April 2003

AbstractA statistical approach to the mechanistic problem of cyclopolymerization was taken. The model for this calculation was based on a stepwise mechanism for polymerization of 1,6‐dienes. The assumption was made that a reaction site was formed at the second carbon of the chain C2, and the probability of C7 being in a volume element surrounding this position was calculated. The results, which indicate that on a statistical basis only, monomer concentrations must be reduced to <0.10 mole/l. in order to attain >95% cyclization, were compared with numerous experimental results in which 95–100% cyclization was obtained at monomer concentrations of 1.9–8.0 mole/l.
Polymerization of acrolein by redox initiation
Authors: Ryder E. E. , Pezzaglia P. 
Published: April 2003

AbstractThe kinetics of the free‐radical‐catalyzed redox polymerization of aqueous acrolein have been examined. The reaction was found to be second‐order in acrolein, half‐order in instantaneous concentration of reducing agent, and independent of peroxide as long as sufficient amount was present. The reaction has a negative temperature coefficient, decreasing in rate as the temperature is raised. The redox system used was tert‐butyl hydroperoxide–polyacrolein hydroxysulfonic acid, and the rate of initiation was observed to vary directly with the pH and the temperature. Polymer molecular weight varied directly with acrolein concentration and indirectly with polyacrolein hydroxysulfonic acid concentration and the temperature. An empirical relationship may be represented as: [η] = K[M0]/[C0]1/4, where [η] is intrinsic viscosity (in deciliters per gram), [M0] is the initial acrolein concentration, [C0] is the initial reducing agent concentration; and K is a temperature‐dependent variable. The effect of trace impurities in acrolein on polyacrolein preparation was examined. Acetaldehyde and propionaldehyde had a retarding effect on polymerization rate. The effect of these components in reducing the molecular weight of the product increased in the order: acetaldehyde, propionaldehyde, and acetone.
Thermoplastic properties of polyacrolein and its acetals
Authors: Fischer R. F. , Stewart A. T. 
Published: April 2003

AbstractFree‐radical polyacrolein is an essentially pure head‐to‐tail vinyl polymer which results in its being a poly‐ 1,5‐dicarbonyl compound. The proximity of these carbonyl groups results in a partial cyclization (laddering) in the polymer or in its derivatives, which in turn has about the same effect on modulus as adding methyl groups to the backbone chain of a polyacrylate or pendant phenyl groups to the backbone chain of polyethylene. Above a viscosity‐average molecular weight of about 200,000, respectable high polymer properties are attained, comparable to those of poly(methyl methacrylate) or polystyrene with higher heat deflection temperatures. Although thermal properties are sufficient to withstand boiling water, actual water and solvent resistances are marginal to poor.
Glass temperature and crystal modification of linear polymethylene
Authors: Magill J. H. , Pollack S. S. , Wyman D. P. 
Published: April 2003

AbstractThe preparation of high molecular weight linear polymethylene is described at low temperatures. The onset of a polymorphic transformation (triclinic to orthorhombic) is observed on warming this low crystallinity (∼50%) polymer to about −25°C. Relative rates of transformation above this temperature are also given. No significant increase in crystallinity occurs on warming the polymer up to room temperature, where some triclinic phase still persists. Annealing polymethylene at 100°C. leaves only the orthorhombic material which is approximately 80% crystalline. A glass transition temperature around −30°C., is reported for the low crystallinity polymer.
Effect of some additives on the crystalline transformations of polybutene‐1
Authors: Rubin I. D. 
Published: April 2003

AbstractDifferential thermal analysis (DTA) was used to study the effect of α‐chloronaphthalene, diphenyl ether, glycerin, and carbon black on the solid‐state transformation of form II to I and the high‐temperature transition of form III to II of isotactic polybutene‐1. α‐Chloronaphthalene and diphenyl ether greatly accelerated the transition of II to I while glycerin and carbon black had no appreciable effect on it. The differences in the rates are attributed to variations in the ability of the additives to create defects which would aid in the nucleation and, possibly, growth of the new crystalline phase. The DTA thermogram of structure III crystallites normally shows two peaks. The addition of α‐chloronaphthalene and diphenyl ether to structure III crystallites resulted in a DTA thermogram with only one peak. Glycerin and carbon black had no effect on the thermogram. These results are discussed in relation to a possible mechanism for the transformation.
Terpolymers of ethylene and propylene with d‐limonene and β‐pinene
Authors: Magin Ralph W. , Marvel C. S. , Johnson Edward F. 
Published: April 2003

AbstractAn experimental program was undertaken to produce a series of ethylene–propylene terpolymers containing either limonene (dipentene) or β‐pinene from a variety of Ziegler‐Natta type catalysts. All attempts to obtain a satisfactory vulcanizate from the limonene EPT and β‐pinene EPT rubbers were unsuccessful.
Kinetics of reaction of ferricyanide with mercaptan solubilized in polystyrene latex
Authors: Meehan E. J. , Kolthoff I. M. , Tsao M. S. 
Published: April 2003

AbstractThe rate of reaction of ferricyanide with n‐octyl mercaptan solubilized in polystyrene latex has been measured. The mercaptan was dissolved completely in the latex polymer particles before the addition of ferricyanide. The latices were prepared with potassium myristate, sodium tetradecyl sulfate, and dodecylammonium chloride, as surfactants. In each latex the reaction was first‐order to ferricyanide, mercaptan, and hydroxyl ion. The rates in myristate and tetradecyl sulfate latices were approximately equal, but smaller by about five orders of magnitude (extrapolated to the same pH) than the rate in the dodecylammonium chloride latex. The reaction apparently occurs on the surface of the polymer particles and thus is favored in the latex with positively charged particles on the surface of which the ferricyanide is adsorbed as counterion.