bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular configuration of branched macromolecules
Authors: Notley N. T. 
Published: April 2003

AbstractMacromolecules with very long backbone and a multiplicity of side chains have been prepared. Polystyrene with stearylamido and polystyrene with laurylamido side chains were obtained by the copolymerization of p‐vinylstearanilide and of p‐vinyllauranilide with styrene. Polymers were made suitable for configurational studies by repetitive precipitation fractionation. Light‐scattering and viscosity studies on dilute solutions indicated however that the effect of side chains on molecular volume was secondary in importance to the effect of variations in fractionation efficiency. Hydrogen succinate side groups on secondary cellulose acetate were obtained by a reaction on the polymer which was demonstrated to be nondegradative. A series of polymers was obtained with the same backbone molecular weight and varying substitution. A steric parameter was derived from viscosity measurements in acetic acid and its dependence on increasing extent of succinylation showed a progressive stiffening of the cellulose chain.
On the fractionation of polypropylene by coacervation
Authors: Redlich O. , Jacobson A. L. , McFadden W. H. 
Published: April 2003

AbstractIn the development of a method for the molal weight fractionation of polypropylene some solubility data were collected. Consistent fractionation results were obtained. The size of the fractions (several grams) was sufficient for the investigation of the influence of the molal weight and its distribution on various properties.
The nature of active components in catalytic systems prepared from TiCl3, monoalkylaluminum dihalides, and electron‐donor substances, in the polymerization of propylene
Authors: Zambelli A. , Dipietro J. , Gatti G. 
Published: April 2003

AbstractThe reaction of two molecules of AlRCl2 with an electron donor molecule D, gives rise to the practically quantitative formation of AlR2Cl and AlCl3.D. This can explain the catalytic activity in the stereospecific polymerization of propylene to isotactic polymer of the systems prepared from violet TiCl3, AlRCl2, and an electron‐donor substance. These systems have the same degree of stereospecificity as the systems consisting of AlR2ClTiCl3 (violet).
Homogeneous anionic polymerization. I. Molecular weights of polystyrene initiated by sodium naphthalene
Authors: Morton Maurice , Milkovich Ralph , McIntyre D. B. , Bradley L. J. 
Published: April 2003

AbstractA study has been carried out on the molecular weight distributions of polystyrene initiated by sodium naphthalene in tetrahydrofuran solution. Stringent high‐vacuum techniques were used in order to minimize initiator destruction or chain termination. Molecular weights were measured by osmotic pressure, dilute solution viscosity, light scattering and sedimentation equilibrium. In general, the molecular weight distributions found were quite narrow, as predicted, and corresponded to a stoichiometry of one polymer chain for two initiator molecules. However, the breadth of the distribution was very sensitive to experimental conditions, the M̄w/M̄n values found ranging from 1.1 to 1.5. At the higher molecular weights, there was some indication of a chain transfer reaction, leading to a lower molecular weight than expected, as well as a broadening of the distribution. This transfer reaction did not appear to be due to any transfer step between the short‐lived radical‐anions and the solvent.
Homogeneous anionic polymerization. II. Molecular weight of polystyrene initiated by lithium alkyls
Authors: Morton Maurice , Rembaum A. A. , Hall J. L. 
Published: April 2003

AbstractA study has been carried out on the molecular weights and their distribution for polystyrene prepared by means of ethyl and butyl lithium initiators, using benzene and tetrahydrofuran as solvents. Stringent high vacuum techniques were employed in order to minimize any destruction of initiator or termination of growing chains in these anionic polymerizations. Under these conditions, it was found that the stoichiometry corresponded to the formation of one chain from each initiator molecule. Furthermore, the molecular weight distribution could be made very narrow (M̄w/M̄n = 1.05 – 1.1) in these cases, where the initiation reaction was very rapid compared to the propagation step. In the case of the benzene systems, the initiation reaction was too slow, leading to a broadening of the molecular weight distribution, and this could be circumvented by a “seeding” technique whereby all the chain anions were pre‐initiated before the main polymerization took place. The alkyl lithium initiators were found to react rapidly with THF at room temperature, but the styryl lithium apparently did not.
Effect of solid polymer interaction on transition temperature and diffusion coefficients
Authors: Kumins Charles A. , Roteman Jerome 
Published: April 2003

AbstractIt has been shown that a nonreinforcing solid such as titanium dioxide can radically alter the glass transition temperature of the model polymer, poly(vinyl chloride–vinyl acetate) copolymer after being mechanically incorporated within it. The Tg values were either higher or lower than that of the original unfilled polymer, depending on the volume fraction of the solid. The magnitude of these changes is in some cases as great as 49°C. This phenomenon was explained on the basis of adsorption of the acetate radicals on the surface of the solid and the breaking of interchain hydrogen bonds. The changes in segmental mobility of the polymer as indicated by the variation in Tg were also verified by gaseous diffusion studies.
Radiation‐induced graft polymerization of styrene to nylon
Authors: Odian George , Sobel Marjorie , Rossi Albert , Klein Robert , Acker Terese 
Published: April 2003

AbstractIt was observed in the gamma radiation‐induced graft polymerization of styrene to nylon that dilution of the styrene with methanol greatly accelerates the rate of styrene grafting. The compositions of the solutions absorbed by the nylon on equilibration with the various methanol—styrene solutions were determined. These results showed that the concentration of styrene available for the grafting reaction is much greater when the styrene—methanol solutions are employed than when undiluted styrene is employed. It was found that the values of k/kt for these graft polymerizations are increased by a factor of 105 compared to the corresponding value in homopolymerization. These increases in the k/kt term are ascribed to the greater viscosity of the medium in which the grafting reaction takes place and to the immobilization of the graft polymer chains by the Trommsdorff‐type effect of methanol. A discussion is presented of the applicability of steady‐state kinetics, as well as of the various competing reactions, in the graft polymerization.
Polymerization of phosphonitrilic chloride trimer at high pressures and temperatures
Authors: Soulen J. R. , Silverman M. S. 
Published: April 2003

AbstractPolymerization of phosphonitrilic chloride trimer at pressures of 10 kbars and above has shown that increasing pressure favors the formation of the rubbery high polymer thermodynamically, but slows its rate of formation. There appears to be no difference in hydrolytic or thermal stability between elastomer formed under high pressure conditions and that obtained by the more usual polymerization at 1 atm.
Polymer NMR spectroscopy. VIII. The influence of the pH of the polymerization medium on the stereochemical configuration of polymethacrylic acid
Authors: Bovey F. A. 
Published: April 2003

AbstractIt is shown that when methacrylic acid is polymerized in an aqueous system, the stereochemical configuration of the polymer, deduced by observation of the high resolution NMR spectra of polymethyl methacrylate samples prepared by methylation, is markedly influenced by the pH of the system. Syndiotactic propagation is favored at higher pH, presumably because coulombic repulsion between negatively charged monomer and negatively charged growing polymer radicals increases the free energy of activation for isotactic monomer placement.
Gas transmission in irradiated polyethylene
Authors: Bixler Harris J. , Michaels Alan S. , Salame Morris 
Published: April 2003

AbstractThe transmission of helium, nitrogen, methane and propane was studied in samples of a high pressure, branched polyethylene (46% crystalline) irradiated to a dose in air of 108 roentgens from a Co60 source. By using a time‐lag apparatus the permeability, diffusion, and solubility constants were measured in the temperature range 0‐55°C. These data were compared with those obtained in samples of the above polymer beforeirradiation. Infrared analysis indicates that oxidation, unsaturation, and croaslinking had resulted from irradiation of the polymer. Because of a possible gradient in chemical composition through the irradiated films, the usual analysis of the time‐lag data may not have been applicable to the present work. The apparent diffusion and solubility constants were, however, qualitatively consistent with the anticipated effects of the chemical and physical changes resulting from irradiation. The apparent solubility constants were uniformly higher by 40% in the irradiated film as compared to the values in the unirradiated films. No reduction in crystallinity was observed upon irradiation, so this increase was ascribed to the effect of chemical composition changes. A thermo‐dynamically consistent increase in the apparent heats of solution was also observed. The apparent diffusion constants were lower in the irradiated samples with the fractional reduction increasing with gas molecular diameter. The reduction for helium was 30%, while that for propane was 54%. The apparent energies of activation for diffusion showed no significant change upon irradiation. Arguments are presented to indicate that the reduced apparent diffusion constants apparently arose from the mild cross‐linking which had occurred in the amorphous phase. Comparisons are made between the gas transmission data obtained in the unirradiated samples with those for other high pressure, branched polyethylenes studied in this laboratory in light of a simple model for gas flow in the crystalline‐amorphous matrix.
Depolarization measurements of polymer solutions at high dilutions. Part II
Authors: Kalpagam V. , Rao M. Ramakrishna 
Published: April 2003

AbstractDepolarization measurements of transversely scattered light were determined for well fractionated samples of poly(methyl methacrylate) in methyl ethyl ketone and a critical consolute mixture of methyl ethyl ketone and isopropanol (1 : 1 by volume). ρu and ρv in methyl ethyl ketone decrease with increasing concentration and tend to become constant above a certain critical concentration, while in the critical consolute mixture, the values decrease steadily with increasing concentration. The ρh values increase with increasing concentration in methyl ethyl ketone, while in the critical consolute mixture they are independent of concentration; this indicates that the size does not change in critical consolute mixture. The individual components Hv and Vv are analyzed for the poly(viny1 acetate) and poly( methyl methacrylate) systems studied by plotting Hv,/C and Vv,/C versus concentration. The observed discrepancies from Doty's predictions are explained.
Viscosities of dilute solutions of polymethyl methacrylate
Authors: Moore W. R. , Fort R. J. 
Published: April 2003

AbstractViscosities of dilute solutions of six fractions of polymethyl methacrylate in the molecular weight range of 48,000–400,000 have been obtained with benzene, toluene, chloroform, tetrachloroethane, and n‐amyl methyl ketone as solvents at different temperatures in the range 25–60°C. There is evidence for association of polymer in amyl methyl ketone, and degradation in tetrachloroethane is possible at higher temperatures. Variations of [η] and of k′ with solvent agree generally with those observed by other workers. Where comparison is possible, values of K and a in the expression [η] = KMa are also in general agreement with other values. Values of K′ in the Flory equation [η] = K′M1/2/α3 may possibly vary with solvent, and it is suggested that in cases where solvation of polymer occurs, the chains may be prevented from adopting the unperturbed configuration adopted in less polar solvents. [η] increases with increase of temperature in all cases but that of tetrachloroethane, but there appears to be a maximum value near 53°C. with both benzene and amyl methyl ketone. The variation of the exponent a with temperature is similar to that of [η]. In the cases of benzene and chloroform, the temperature coefficient of [η] seems to be primarily due to changes in the value of the swelling factor α, but in other cases changes in the value of (r̄02/M) are important, r̄02 being the mean square unperturbed end‐to‐end distance of the polymer chains.
Éatude de l'influence du tetrahydrofurane sur la radioreticulation du chlorure de polyvinyle
Authors: Wippler C. , Gautron R. 
Published: April 2003

AbstractIn this paper an attempt was made to explain the crosslinking mechanism of PVC, when irradiated in the presence of tetrahydrofurane. Taking into account several experimental results, a very likely conclusion seems to be that a bridge between two PVC molecules consists in a THF molecule, of which the ring has been opened by the combined effects of the irradiation and of the chlorine or hydrochloric acid evolved from the PVC.
Syndiotactic polyvinyl formate and derived polyvinyl alcohol
Authors: Rosen Irving , McCain G. H. , Endrey A. L. , Sturm C. L. 
Published: April 2003

AbstractA study was made of the effect of polymerization temperature on the syndiotacticity of polyvinyl formate. Vinyl formate was polymerized with ultraviolet light initiation in the temperature range from −20 to +30°C. The value of (Ep — Et)/2 obtained, 4.5 kcal./mole, is characteristic of those values obtained by other workers for the free radical‐initiated polymerization of vinyl acetate. A linear relationship was found to exist between the viscosities of the polyvinyl formates and those of the derived polyvinyl alcohols. The degree of polymerization of polyvinyl formate may be calculated from the equation: [η] = 4.42 × 10−3 DP0.63. The low temperature polymerization of vinyl for‐ mate results in more syndiotactic polymer, as shown by x‐ray diffraction. Polyvinyl for‐mate obtained at more elevated polymerization temperatures did not demonstrate the same degree of order. No difference was found between the infrared spectra of the polyvinyl formates. The polyvinyl alcohol derived from polyvinyl formate polymerized at low temperatures (0 to −35°C.) exhibits water resistance and forms a colored iodine complex similar to that obtained with the syndioactic polyvinyl alcohol derived from polyvinyl trifluoroacetate. Conventional polyvinyl alcohol and that derived from polyvinyl acetate polymerized at −30°C. do not exhibit the same properties. Minor differences in the 1,2‐glycol content in the various polyvinyl alcohols do not account for the differences in the observations. The amount of head‐to‐head addition in various vinyl aliphatic esters seems to be related to the inductive strength of the acid portion of the ester. No difference was found between the crystallinities of the various polyvinyl alcohols, as measured by film density. Heat treatment increases the crystallinities about the same amount, but the water resistance of the stereoregular materials remains higher. From the good correlation between the observations made on polyvinyl formate and the derived polyvinyl alcohol, it is concluded that syndiotactic polyvinyl formate, and hence syndiotactic polyvinyl alcohol, is obtained by the low temperature free radical‐initiated polymerization of vinyl formate. Increased syndiotacticity is more readily obtained in polyvinyl formate than in polyvinyl acetate, indicating the greater influence of inductive effect compared with the steric effect in controlling stereoregularity during free‐radical propagation.
Polyethers. XI. Polymerization ofDL‐propylene oxide with optically active catalyst systems
Authors: Chu Nan Shieh , Price Charles C. 
Published: April 2003

AbstractThe polymerizations ofL‐propylene oxide by aluminum isopropoxide–zinc chloride, ferric chloride–propylene oxide, and diethylzinc–water catalysts have been studied further and analyzed in terms of the source of stereocontrol in producing isotactic crystalline polymer. The polymerization ofDL‐propylene oxide by optically active complexes of the above catalysts with poly(L‐propylene oxide) and with a catalyst formed from triisobutylaluminum andL‐propylene glycol failed to produce any evidence for stereopreference by the catalysts for theL‐ orD‐molecules.
Copolymerization studies. III. Reactivity ratios of model ethylene copolymerizations and their use in Q–e calculations
Authors: Burkhart R. D. , Zutty N. L. 
Published: April 2003

AbstractMonomer reactivity ratios for the copolymerization of ethylene (M2) with n‐butyl acrylate, vinyl chloride, vinyl acetate, and vinyl fluoride have been measured at 1000 atm. The respective values and the experimental temperatures are r1 = 11.9, r2, = 0.03, 70°C.; r1 = 3.6, r2 = 0.24, 90°C.; r1 = 1.08, r2 = 1.07, 90°C.; r1 = 0.16, r2 = 4.39, 160°C. Price Q and e values for ethylene calculated from these reactivity ratios, uncorrected for differences in reaction pressure, are 0.03 and −0.43, respectively. New Q and e values (Q0 and e0) for these four comonomers were calculated on the basis of ethylene rather than styrene as the reference monomer. Assuming that the Q0 and e0 values for ethylene are 1.0 and zero, respectively, the monomer's Q and e0 value are as follows: n‐butyl acrylate, 33.3, + 1.02; vinyl chloride, 4.2, + 0.37; vinyl acetate, 0.93, ∼0; vinyl fluoride, 0.25, + 0.6. These Q0 and e0 values give calculated reactivity ratios which are in reasonable agreement with experimental ones. Good agreement is also obtained when the r2 value for the vinyl acetate/ethylene copolymerization is compared with the directly determined rate constant ratio for the addition of an ethyl radical to ethylene and to vinyl acetate, respectively, calculated from previously published data.
Diffusion‐controlled polymerization of some alkyl methacrylates
Authors: North A. M. , Reed G. A. 
Published: April 2003

AbstractA study has been made of the nonstationary‐state free‐radical polymerization of methyl, n‐butyl, isobutyl, and 3,5,5‐trimethylhexyl methacrylate in mixed solvents of varying viscosity. It has been found that the termination reaction is diffusion controlled over the complete viscosity range in each case. Values of the ratio kt/kp have been obtained for each monomer in ethyl acetate solvent. The relative decreases in this ratio as the size of the alkyl group increases have been compared with decreases calculated (a) on the basis of translational diffusion of macroradicals controlling termination, (b) on the basis that segmental diffusion of the radical chain end in the coiled polymeric free radical is the rate‐controlling process in termination. Although it has been necessary to consider an oversimplified model of segmental diffusion, the calculated dependence of kt on the size of the alkyl group is in accord with that observed experimentally, whereas decreases calculated on the basis of translational diffusion do not agree with those observed. The results are interpreted as signifying that segmental diffusion of the radical chain end is the rate‐determining step in the termination of the free‐radical polymerization of the alkyl methacrylates, and as providing a simple method of calculating the relative values of the diffusion‐controlled termination rate constant for the polymerization of different monomers.
Syntheses of polyanhydrides. XII. Crystalline and high melting polyamidepolyanhydride of methylenebis(p‐carboxyphenyl)amide
Authors: Yoda Naoya 
Published: April 2003

AbstractThe acid‐catalyzed condensation of formaldehyde and aromatic nitrile has been investigated. Methylenebis(p‐carboxyphenyl)amide was synthesized in 90% yield by the interaction of p‐cyanobenzoic acid with formaldehyde under the influence of conc. sulfuric acid. Polycondensation of methylenebis(p‐carboxyphenyl)‐amide was carried out with acetic anhydride at 260–365°C. under vacuum and under a N2 atmosphere. The linear crystalline polyamidepolyanhydride thus obtained has a melting point at 325–330°C. and exhibits excellent stability towards thermal and hydrolytic degradation. It was confirmed from the experimental evidence that the introduction of the amide linkage in the main chain of the polymer increases the melting temperature of crystallite owing to the formation of intermolecular hydrogen bonds within the molecule of polyanhydride repeating unit. The molecular structure was inferred on the basis of infrared spectra and the x‐ray diffraction pattern of the polyamidepolyanhydride. The correlation between cohesion energy per chain unit and crystalline melting temperature of various aromatic and aliphatic polyanhydrides is discussed in detail.
Oxidative crosslinking of polyethylene by ultraviolet light
Authors: Cotten G. R. , Sacks W. 
Published: April 2003

AbstractThe mechanism of weathering damage in polyethylene films was studied by measurement of molecular weight (by intrinsic viscosity), content of xylene‐insoluble fraction (gel), and carbonyl group concentration (by infrared analysis) in exposed samples. Results obtained indicate that both chain scission β and crosslinking α occur simultaneously. The effect of thickness and crystallinity of the polyethylene films suggest that the ratio β/α may be dependent upon the oxygen concentration at the site of reaction and, therefore, the rate of penetration of oxygen through the film, at constant intensity of absorbed light. The chain scission reaction appears to be favored in highly crystalline regions.
Inhibition kinetics of the polymerization of styrene. II. Investigations on the effect of s‐trinitrobenzene
Authors: Tüdös Ferenc , Kende Imre , Azori Mária 
Published: April 2003

AbstractThe kinetics of the polymerization of styrene initiated by azo‐bis‐isobutyronitrile was investigated in the presence of s‐trinitrobenzene (TNB). According to the experimental results, the TNB behaves like a weak inhibitor and is transformed into a retarder during the inhibition period. The kinetic laws of this case of inhibition are not known from literature. Therefore, the fundamental kinetic relations of inhibition accompanied by retardation were elaborated. The kinetic equations for the rate of the inhibited polymerization and for the consumption of the inhibitor were deduced. A method was elaborated for the calculation of the length ti of the inhibition period from the apparent inhibition period t' to be determined by extrapolation from the measured dilatometric data. The experimental results obtained with TNB at 40, 50, and 60°C. can be well interpreted by the deduced kinetic relations. According to the computations, the number of macroradicals deactivated by one TNB molecule amounts to 3.14 ± 0.1 at 40°C., 2.98 ± 0.1 at 50°C., and 2.89 ± 0.2 at 60°C. It is pointed out that this surprising value of the stoichiometric coefficient cannot be interpreted by trivial considerations. Finally, the relative reactivity of the TNB compared to that of the monomer as well as the dependence of this reactivity on temperature were determined.