bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of transition metal salts in polyglycol autoxidations
Authors: Lloyd W. G. 
Published: April 2003

AbstractThe addition of small amounts of transition metal salts, e.g., CuCl2, to low molecular weight polyoxyalkylenediols results in pronounced autoxidation inhibition. This is in contrast with McGary's findings that this same class of salts accelerates the autoxidative degradation of high molecular weight polyethylene glycols. Inhibition of diethylene glycol is shown to relate to catalyzed hydroperoxide decomposition. With polyoxyethylenediol of molecular weight 600 this inhibition with CuCl2 is less pronounced, and with both polyoxyethylene diols and polyoxypropylene diols the inhibitory effect gives way to a net accelerating effect with increasing polymer molecular weight. The inhibitory effect is insensitive to increasing medium polarity and to changes in oxygen pressure, but is markedly sensitive to terminal group capping. Combinations of appropriate metal salts and organic antioxidants produce synergistic stabilization. The results may be explained by postulating a competition between the normal radical‐generating reactions of hydroperoxides with transition metal ions and the formation of specific terminal‐hydroperoxide complexes which decompose heterolytically.
Heterogeneous membranes: Diffusion in filled rubber
Authors: Barrer R. M. , Barrie J. A. , Rogers M. G. 
Published: April 2003

AbstractThe diffusion and solution of propane and of benzene has been studied over a range of temperatures in a series of heterogeneous membranes of natural rubber and zinc oxide filler. The volumes of filler were 0, 5, 10, 20, 30, and 40%. Evidence was obtained of the interaction between rubber and filler, and that some of the membranes involved three phases: polymer, filler, and open gaps between filler particles. No rigorous treatment of diffusion in heterogeneous media exists, but the model of two interdispersed phases was developed and discussed in relation to permeation rates and diffusion coefficients. Differences between steady state and time‐lag diffusion coefficients were ascribed to different structure factors in steady and transient states of flow. Concentration dependences of the interdiffusion and intrinsic diffusion coefficients of benzene were measured. The influence of concentration dependence, filler, and structure factor was combined in one relationship relating the intrinsic diffusion coefficient in the filler rubber with that for diffusion in unfilled rubber, containing the same volume fraction of benzene. The resultant expression appears able to account qualitatively for some of the observed complex diffusion behavior.
The emulsion polymerization of 2,3‐dimethylbutadiene‐1,3
Authors: Morton Maurice , Gibbs William E. 
Published: April 2003

AbstractA study has been carried out on the kinetics of the emulsion polymerization of 2,3‐dimethylbutadiene‐1,3. The kinetic treatment of Smith and Ewart was applied for the direct determination of the absolute propagation rate constant kp. The following expression was obtained: kp = 8.9 × 107 exp {−9000/RT} liter/mole/sec. A previously developed treatment was applied to the determination of the relative and absolute crosslinking rates of 2,3‐dimethylbutadiene‐1,3. The results led to the following expression for the absolute crosslinking rate constant kx: kx = 3.0 × 106 exp {−14400/RT} liter/mole/sec. A comparison of these rate constants was made for the three dienes, viz., butadiene, isoprene, and dimethylbutadiene. The propagation rate constants were found to vary only by a factor of 2–3. However, the crosslinking rates were found to decrease considerably in going from butadiene to isoprene to dimethylbutadiene. This was attributed, mainly, to the decreased side‐vinyl content of the latter two monomers, compared to butadiene, as well as to the steric hindrance imposed by the presence of the methyl group.
Transannular polymerization of 1,5‐cyclooctadiene
Authors: Reichel Bernd , Marvel C. S. , Greenley R. Z. 
Published: April 2003

AbstractThe polymerization of 1,5‐cyclooctadiene to a low molecular weight polymer utilizing a Ziegler‐type catalyst composed of triisobutylaluminum and titanium tetrachloride is reported. Although the structure of the polymer has not been definitely established its spectral and other physical properties suggest it to be poly‐2,6‐bicyclo(3,3,0)octane. Under the same conditions 1,4‐cyclohexadiene did not undergo a transannular polymerization reaction but rearranged and yielded poly‐1,3‐cyclohexadiene.
Polymerization in liquid sulfur dioxide. Part XIII. Polymerization of styrene derivatives in liquid sulfur dioxide
Authors: Tokura Niichiro , Matsuda Minoru , Ogawa Yasuo 
Published: April 2003

Abstractp‐Bromostyrene, p‐methylstyrene and α‐methylstyrene were subjected to polymerization in liquid sulfur dioxide with α,α'‐azobisisobutyronitrile as an initiator at polymerization temperatures of 0–60°C. In case of polymerization of p‐bromostyrene, only polysulfones of 1:2 molar ratio between sulfur dioxide and p‐bromostyrene were obtained. No cationic polymerization was observed. In case of polymerization of p‐methylstyrene polysulfone having 1:2 composition, a radical polymerization product, as well as poly‐p‐methylstyrene, a cationic polymerization product, as obtained, revealing concurrent and competitive occurrence of both polymerizations. The cationic polymerization was explained as the result of the electron‐donating property of the para‐methyl substituent and the catalytic action of sulfur dioxide or sulfurous acid formed with a minute amount of water contained in liquid sulfur dioxide. In liquid sulfur dioxide, the cationic polymerization was perfectly inhibited by DMF and the radical polymerization was not affected by the presence of DMF. In a system in which the radical polymerization alone proceeded in liquid sulfur dioxide, the overall rate of the polymerization was proportional to the concentration of AIBN in the order of 0.7. This was interpreted to indicate that the strong solvation between sulfur dioxide and the terminal radical of the growing radical due to hyperconjugation of the p‐methyl group may stabilize the terminal radical, leading to a unimolecular termination. In the polymerization of α‐methylstyrene, the addition of AIBN did not give polysulfone, but gave poly‐α‐methylstyrene alone as a result of cationic polymerization.
Some applications of afterglow studies of luminescent compounds in solid polymers
Authors: Czarnecki Stefan , Kryszewski Marian 
Published: April 2003

AbstractThe afterglow (β‐band luminescence) observed in polymethyl methacrylate activated with different hydrocarbons such as naphthalene and its derivatives was found to be sensitive to the influence of oxygen. The sharp boundary between the luminescent and nonluminescent area is due mainly to the diffusion of oxygen and shifts with time from the edges to the center of the specimen. The recovery of the afterglow results on H2 diffusion into the polymer sample or after ultraviolet irradiation. An interpretation of the observed phenomena as well as the application of the afterglow moving boundary technique to the determination of diffusion coefficients of gases in polymers and to the studies of some related processes is suggested.
Fibrous structure in stretched crystalline elastomers
Authors: Walters M. H. 
Published: April 2003

AbstractStress‐induced crystallinity in elastomers produces a strengthening structure, and tearing the rubber along the axis of extension leaves this structure outlined in the rupture surface. By maintaining the initial elongation, and taking replicas of this torn surface, the morphology of stress crystallinity has been examined in the electron microscope. The crystallites were found to be closely spaced fibers, rounded in section, and oriented in the direction of elongation. The fibers were usually between 100 and 1000 A. in diameter, and individual crystallites could be traced for distances of several microns before disappearing beneath the exposed surface. Noncrystallizing polymers showed no structure in the rupture surface. The addition of fine particle fillers had little effect on the structures observed in crystallizing polymers. In amorphous polymers traces of structure were observed, apparently consisting of groups of carbon black particles linked by rubber molecules.
Zone‐refining fractionation of polymers
Authors: Loconti Joseph D. , Cahill John W. 
Published: April 2003

AbstractThe unidirectional freezing of dilute solutions of polystyrene in benzene yields a frozen charge with a high concentration gradient, low in the first part frozen and highest in the last. A substantial heterogeneity in molecular weights is also noted, the highest molecular weight being found in the first part and progressively lower molecular weights toward the terminal end of the charge. Both concentration and molecular weight changes are strongly dependent upon freezing rate, low rates favoring maximum concentration changes and intermediate rates favoring maximum molecular weight separation. The application of these observations to a polymer fractionation system is reported.
Rheological measurements on polycarbonate
Authors: Baumann Gert F. , Steingiser Samuel 
Published: April 2003

AbstractRheological properties of polycarbonate were measured at constant shear stress and at constant shear rate using a capillary rheometer. The melt viscosity of polycarbonate was determined as a function of: (1) weight‐average molecular weight and molecular weight distribution in the range of M̄w = 13,000–80,000 and M̄w/M̄n = 1.1–3, respectively; (2) temperature at 260–316°C.; (3) shear rates of 1–300 sec.–1; (4) “Processability” as experienced in the injection‐molding range. A straight‐line relationship between long ηm and log M̄w was found with a slope of 3.2. A plot of log ηm against log M̄n resulted in a family of straight lines of the same slope but whose intercepts depended on the polydispersity ratios. The activation energy of viscous flow was calculated from a plot of log ηm versus 1/T at various shear rates. It varied from 26–30 kcal./mole at low shear rates to about 16 kcal./mole at higher shear rates. A shear stress versus shear rate plot showed that polycarbonate exhibited almost Newtonian behavior at temperatures above 290°C. Finally, a good correlation was established between the data obtained on the capillary rheometer and that obtained in an injection‐molding test using a spiral mold.
Electron spin resonance studies of the reaction of gases with the radicals formed in irradiated polytetrafluoroethylene
Authors: Ueda Hisashi , Kuri Zenichiro , Shida Shoji 
Published: April 2003

AbstractThe effect of O2, SO2, NH3, H2S, and NO on the ESR of irradiated PTFE were studied. Radicals were produced by (1) irradiation of PTFE in an atmosphere of one of these gases and (2) by the postirradiation reaction of PTFE with this same gas. These radicals were subsequently reacted with each of the remaining four gases, and the resulting spectra were studied. The radical produced in PTFE by the irradiation in vacuum is quenched by NO. In this reaction, the relation between the number of quenched radicals and the pressure of NO was measured, showing that the relation can be expressed by Freundlich's equation for adsorption equilibria. From these data, the bonds formed by the reaction between the gases and the radicals, the classification of the radical and the structure of these radicals were discussed.
Monte‐carlo calculations of the dimensions of coiling type polymers in solutions of finite concentration
Authors: Bluestone Sydney , Vold Marjorie J. 
Published: April 2003

AbstractThe mean end‐to‐end distances for linear polymers of 101 segments has been computed for nonintersecting random walks on a five‐choice cubic lattice on which a second chain is also present, as a function of the distance between the two chains (i.e., polymer concentration). The polymer dimensions appear to decrease with concentration, linearly at first and then more slowly. The results compare favorably with experiment and with some of the approximate analytic theories and poorly with others.
Linear condensation polymers from phenolphthalein and related compounds
Authors: Morgan P. W. 
Published: April 2003

AbstractPhenolphthalein, phenolphthalimidine, phenolisatin, and similar compounds were found to react as bisphenols with aliphatic and aromatic diacid chlorides, bischloroformates, and phosgene to form linear, high molecular weight products. Interfacial and low and high temperature solution polycondensation procedures were used. The polymers were colorless and readily formed films or fibers from a wide variety of solvents. Several peculiarities in solubility behavior were encountered. The glass transition and melting temperatures of all of the polymers were much higher than values for similar polymers derived from bisphenol A. Water absorption was relatively high, and stability to discoloration by ultraviolet light was good. The majority of the products did not crystallize readily.
Polymers from sulfamide. I. Preparation
Authors: Smith H. Q. , Scott F. L. 
Published: April 2003

AbstractSulfamide and formaldehyde react at pH 10 to give a polymeric white solid (A) which decomposes at 234–235°C. A similar material results at pH 7. Modification of A was achieved by inclusion of melamine in the polymeric matrix. Sulfamide‐melamine‐formaldehyde polymer had a melting point of 261–265°C., was insoluble in organic solvents, and formed a cohesive film on compression. The polymer was obtained when sulfamide, formaldehyde, and melamine were all allowed to react simultaneously, or when a methylol melamine derivative was first prepared and then crosslinked with sulfamide. Sulfamide appears to be a more rapid crosslinking agent than urea for this system. Other aminotriazines were used in place of melamine and some 1,3‐dialkyl‐sulfamides were employed in place of sulfamide, but no significant improvement in thermal stability of the polymers was achieved.
Polymers from sulfamide. II. Evaluation and structure
Authors: Florentine R. A. , Barth‐Wehrenalp G. , Mockrin I. , Popoff I. , Riordan R. 
Published: April 2003

AbstractAcid‐ and base‐catalyzed polymers involving sulfamide, melamine, and formaldehyde have been prepared and investigated. The products are insoluble and their thermal stability does not exceed 225°C. in N2.
Base‐catalyzed solution polymerization of octamethylcyclotetrasiloxane
Authors: Morton Maurice , Deisz M. A. , Bostick E. E. 
Published: April 2003

AbstractA study has been carried out on the effect of solvent polarity on the base‐catalyzed polymerization of octamethylcyclotetrasiloxane. The solvents used were decalin, p‐chlorotoluene, o‐dichlorobenzene, and nitrobenzene. In accordance with the ionic mechanism proposed by Grubb and Osthoff, it has been found that the polymerization rate increases with solvent polarity, presumably bp increasing the concentration of silanolate ions. In addition, a better correlation has been obtained between molecular weights and initiator concentration, and the effect of monomer concentration on equilibrium conversion has also been elucidated.
Gel permeation chromatography. I. A new method for molecular weight distribution of high polymers
Authors: Moore J. C. 
Published: April 2003

AbstractPolystyrene gels crosslinked in the presence of diluents have been made in fine‐mesh bead form suitable for packing into chromatographic columns. A series of narrow molecular weight range polymer fractions was eluted through such columns with aromatic and chlorinated solvents. Effluent concentrations were detected and recorded by a continuous differential refractometer. The fractions were shown to be efficiently separated. Columns capable of separating adjacent polymeric samples of high molecular weight were prepared from gels crosslinked in the presence of large amounts of diluents having little or no solvent action on polystyrene. Smaller proportions of diluents and those with more solvent action yielded columns with lower molecular weight permeability limits. Such studies provided a unique quantitative view of the topology of the gels. They also demonstrated that rapid repetitive molecular weight distribution data can be obtained in this way on polymers for which solvents compatible with the gels are available.
Electroinitiated anionic polymerization of acrylonitrile
Authors: Funt B. Lione , Williams Fredrick D. 
Published: April 2003

AbstractPolymer was formed by an electrolytically initiated reaction in solutions of acrylonitrile and other monomers in dimethylformamide saturated with sodium nitrate. From analysis of copolymer compositions it was established that the polymer was formed at the cathode by an anionic propagation mechanism. The nature of the chain initiating step was investigated through polarographic measurements. These clearly suggest that chain initiation proceeds via direct electron addition to the double bond. A close correlation between the tendency to form anionic polymer and the polarographic potentials is indicated. The effects of current, time, and monomer concentration on the production of polymer were delineated. The yield of polymer increased linearly with time at fixed current density and showed first order dependence on monomer concentration. The absolute current efficiencies were extremely high and ranged to over 3 polymer molecules formed per electron transferred at the electrode. The molecular weights of the polymers are remarkably independent of monomer concentration, rate, and current density. A reaction scheme is proposed which postulates chain transfer to monomer. A kinetic analysis confirms the consistence of the scheme with experimental findings. Coloration and crosslinking found in some of the polymers are interpreted, and a mechanism is proposed.
Studies in the kinetics of removal of water from cellulosic fibers
Authors: Daruwalla E. H. , Shet R. T. 
Published: April 2003

AbstractA study has been made of the kinetics of the removal of water from native, alkaliswollen, and regenerated cellulosic fibers under well defined conditions of experiment. In all cases, the rate of evaporation curve appears to be made up of five distinct and separate portions, and there are four points on each curve at which sudden changes of direction take place. From the changes in the rates of removal of water, attempts have been made to determine the amounts of water present in cellulosic fibers with different degrees of association with the fiber substance and to compare these values with those recorded by other workers employing different techniques. Removal of primary adsorbed water from different cellulosic fibers could be best represented by three distinct phases, the first two of which obey kinetics of reaction of first order and with apparent activation energy of the order of 8–9 kcal./mole. An attempt has also been made to calculate the radii of capillaries present in water‐swollen cellulosic fibers.
Photosensitized polymerization of acrylic monomers. II. Kinetics of polymerization in the presence of oxygen
Authors: Delzenne G. , Dewinter W. , Toppet S. , Smets G. 
Published: April 2003

AbstractThe kinetics of the photopolymerization of acrylamide and methacrylic acid in aqueous and semi‐organic solutions have been examined; the initiating redox system used in the presence of oxygen were eosin‐thiourea, eosin‐1‐ascorbic acid, or in some cases riboflavine. The rates of photopolymerization were determined by measuring the thermal rise of the reaction cell using a thermistor technique. In aqueous and in semi‐organic solutions, the rate is proportional to the square of the monomer concentration in both cases. Below a critical concentration of sensitizer the rate of polymerization of monomers is proportional to the square root of sensitizer concentration (acrylamide in the presence of riboflavine, methacrylic acid in the presence of eosin‐ascorbic acid); above it, the rate becomes inversely proportional to the square root of the sensitizer concentration. With respect to the reducing agent concentration, the exponent for thiourea is located between 0.5 and 1 in the case of acrylamide and 0.5 for methacrylic acid. Finally with respect to the oxygen concentration the rates are proportional to the square root of its concentration, at least below a given oxygen‐concentration where the induction period becomes predominant. These results are interpreted assuring a participation of the monomer in the initiation step, and a low initiation efficiency of the primary radicals (cage recombination). A kinetic scheme is presented and the experimental results discussed on the basis of it.
Free radical homopolymerization and copolymerization of vinyl phosphines, oxides, and sulfides
Authors: Rabinowitz Robert , Marcus Ruth , Pellon Joseph 
Published: April 2003

AbstractA variety of free radical catalysts failed to homopolymerize diphenylvinylphosphine and diisobutylvinylphosphine oxide. Oligomeric products were obtained with diphenylvinylphosphine oxide and sulfide. It was shown that in the homopolymerization of the oxide at 100 and 130°C., the molecular weight is independent of catalyst concentration. Further a minimum kinetic chain length for the 0.10 mole‐% di‐tert‐butyl peroxideinitiated bulk polymerization at 130°C. was calculated to be 500 units. Reactivity ratios with styrene and methyl methacrylate (MMA) were obtained from copolymerization data (phosphorus monomer is M2). The following r1 values were obtained (all r2 values were close to zero): with diphenylvinylphosphine sulfide: styrene (2.1 ± 0.3), MMA (13 ± 3); with diphenylvinylphosphine oxide: styrene (5 ± 1), MMA (11 ± 4); with diphenylvinylphosphine: styrene (7 ± 1), MMA (5.1 ± 0.2); with diisobutylvinylphosphine oxide: styrene (17 ± 5), MMA (30 ± 10). It was concluded that the phosphorus groups do not exert strong conjugative stabilization of an adjacent carbon radical but can be considered as mildly activating on the basis of a comparison of the relative reactivities of these monomers and a series of common monomers toward a styryl radical.
Synthesis, polymerization, and copolymerization of diphenyl‐p‐styrylphosphine, phosphine oxide, and phosphine sulfide
Authors: Rabinowitz Robert , Marcus Ruth , Pellon Joseph 
Published: April 2003

AbstractDiphenyl‐p‐styrylphosphine (I), prepared by the reaction of diphenylchlorophosphine with p‐styrylmagnesium chloride, was converted to the corresponding oxide (II) and sulfide (III) by treatment with tert‐butyl hydroperoxide and sulfur, respectively. These substituted styrenes polymerize readily with thermal or free radical initiation to high molecular weight polymers. These polymers are somewhat more thermally stable than polystyrene. Thus their Ti's in air were in the range 320–365°C. and in nitrogen, 375–395°C. Their T10's were in the 390–415°C. range in air and 425–435°C. in nitrogen. Polystyrene in air has a Ti of 263°C. and a T10 of 340°C. The monomers copolymerize readily with styrene and methyl methacrylate, the low conversion polymers always containing more phosphorus than the monomer mixtures. Reactivity ratios were determined, from which Q and e values were calculated. These values for the following monomer pairs are (phosphorus monomer M2): styrene‐I, r1 0.52, r2 1.43, Q2 1.34, e2 −0.30; styrene‐II, r1 0.42, r2 1.40, Q2 1.34, e2 −0.07; styrene‐III, r1 0.43, r2 1.49, Q2 1.37, e2 −0.13; MMA‐I, r1 0.32, r2 0.91, Q2 1.58, e2 0.80; MMA‐II, r1 0.38, r2 1.46, Q2 1.42, e2 −0.35; MMA‐III, r1 0.29, r2 1.22, Q2 1.58, e2 −0.62. Analysis of these data indicates that these phosphorus moieties are activating through strong electronegative effects. The extent of activation is intermediate in intensity between mildly activating groups (e.g. Cl) and strongly activating groups (e.g. CN or NO2). The behavior of diphenyl‐p‐styrylphosphine is of particular interest in this respect, since its electronegativity points to strong electron delocalization.