bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photolysis of cellulose in a vacuum with 2537 A. Light
Authors: Flynn Joseph H. , Morrow William L. 
Published: April 2003

AbstractCotton sliver, cotton linters, periodate‐chlorite‐oxidized cellulose, and several regenerated celluloses were photolyzed by 2537 A. ultraviolet light in a vacuum at 40°C. The changes in quantum yields of hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, aldehyde groups, carboxyl groups, and chain scissions with respect to quanta of light absorbed and initial functional group concentration indicated that photolysis of alcohol groups plays a dominant role in the complex of interdependent primary and secondary reactions taking place. Periodate‐chlorite‐oxidized cellulose is much more suceptible to photochemical degradation than is unoxidized cellulose. Neutralization with very dilute sodium hydroxide solution reduced the quantum yields of the oxycellulose to values similar to those obtained with the unoxidized material.
Effects of deuteration and temperature upon the photolysis of cellulose in a vacuum with 2537 A. Light
Authors: Flynn Joseph H. , Morrow William L. 
Published: April 2003

AbstractThe effects of the exchange of deuterium for hydrogen in the hydroxyl groups on the composition of products and the kinetics of their formation during the irradiation of cellulose by 2537 A. in a vacuum at 77, 313, and 365°K. are described. About 50–70% of the total hydrogen evolved was HD. Little D2 was formed. Total HD evolution was independent of temperature. Disproportionation, rather than atom abstraction or atom combination, was likely to be the dominant mechanism of hydrogen production. Much of the aldehyde group formation takes place during the photolysis and probably results directly from secondary photolysis or disproportionation of radicals. H2, CO, and CO2 evolutions increase with temperature and result from both functional group photolysis and radical depropagation. Chain scission and carboxyl group formation take place to a large extent during the post‐irradiative oxidation of long‐lived oxygencontaining radicals.
Covalent acid‐labile crosslinkages in wool
Authors: Crewther W. G. 
Published: April 2003

AbstractThe extent of the first stage of supercontraction of wool fibers in 8M LiBr (20°C.) was unaltered by the incorporation of 1N HCl in the solutions, whereas the extent of total supercontraction (98.5°C.) was greatly increased by the presence of HCl in the LiBr solutions. Likewise, with reduced and methylated wool, the relationship between the extent of the first stage of supercontraction and the content of residual disulfide was not affected by the presence of HCl in the solutions. When reduced and methylated wool fibers containing few residual disulfide groups were allowed to supercontract in solutions containing 8M LiBr and varying concentrations of HCl, the fibers contracted rapidly until the extent of total supercontraction in neutral solutions was approached. The rate then changed suddenly and became directly proportional to the concentration of acid in the solutions. Extensive supercontraction was observed also in alkaline solutions of LiBr if carboxyl groups of the reduced and methylated fibers were first ethylated to decrease the solubility of the wool proteins. Cortical cells, which were prepared by digesting reduced and methylated wool with crude trypsin, resembled whole wool in their behavior. It was concluded that wool contains covalent crosslinkages which are hydrolyzed by acids and alkalies. Evidence is presented that these bonds are stabilized by disulfide crosslinkages. The possiblity that disulfide interchange takes place during supercontraction in solutions of LiBr‐HCl is discussed.
A scattered‐light study of linear polyethylenes
Authors: Stacy Carl J. , Arnett Raymond L. 
Published: April 2003

AbstractA scattered‐light photometer particularly adapted to high temperature work has been designed and constructed. Among the desirable features are constant monitoring of the primary beam, placement of photodetectors outside the heated zone, output proportional to ratio of outputs of matched detectors, thus to Rayleigh's ratio, insensitivity of output readings to light absorption by the solution, temperature control from room temperature to 150°C. The geometrical factors affecting output readings have been analyzed and the instrument calibrated using several standards. Techniques developed for hot solution clarification and the measurement with good precision of weight‐average molecular weights of ethylene polymers are described. The results for several typical unbranched Marlex polyethylenes are given covering the range 80,000–170,000. Depending on the polymer, the ratio weight‐average to number‐average varies from 10 to 16 for whole Polymer. The z‐average molecular weights estimated from the mean‐square molecular radii are used to estimate Mz/Mw ratios.
Emulsion polymerization of vinyl monomers by transition metal compounds
Authors: Berger Richard S. , Youngman E. A. 
Published: April 2003

AbstractA number of transition metal ions and complexes of the type which effect the stereospecific polymerization of butadiene in aqueous emulsion catalyze the polymerization of other vinyl monomers as well. In contrast to experience with butadiene, the structure of all products was typical of free‐radical propagation reactions. The catalysis was somewhat selective, a given transition metal compound being active for some monomers but not for others. A mechanism involving coordinate complex formation between catalyst and monomer, generation of a free‐radical initiator by redox reaction within the complex, and noncoordinated free‐radical propagation is postulated. Copolymerization studies support such a mechanism; copolymer compositions were always typical of free‐radical catalysis, even when the catalyst was active in homopolymerization of only one member of the monomer pair. Butadiene polymerizations using many of the same catalysts clearly proceed by different, little understood mechanisms. Attempted copolymerizations with butadiene gave only polybutadiene; the comonomers had no effect on polymer microstructure but generally reduced polymerization rate.
Cationic polymerization of 3‐methylbutene‐1. I. Polymerizations at moderately low temperatures
Authors: Kennedy J. P. , Minckler L. S. , Thomas R. M. 
Published: April 2003

AbstractThe cationic polymerization of 3‐methylbutene‐1 was investigated with the use of aluminum chloride and aluminum bromide initiators in the temperature range of −62 to −102°C. Polymerizations are homogeneous in the presence of pentane, and above −50°C. in methyl chloride. However, the polymer tends to precipitate below −50°C. in methyl chloride. The molecular weight of poly‐3‐methylbutene‐1 increases with decreasing temperatures at the same conversion level. Significantly, the molecular weights increase with conversion and seem to reach their maximum at high conversions. Higher molecular weights were obtained in n‐pentane‐alkyl chloride mixtures than in methyl chloride solution alone. The molecular weights are independent of catalyst concentrations in the range investigated (31.8–7.97 × 10−4 mole/l. AlBr3 and 57.6–28.8 × 10−4 mole/l. AlCl3). The rate of homogeneous polymerization with aluminum bromide in propane solvent was studied. The rate is first order in monomer concentration and catalyst concentration and the rate constant is 0.610 l./mole sec. The apparent activation energy calculated from the Arrhenius plot is 6.57 kcal./mole. In methyl bromide the rate of polymerization increases significantly (effect of the dielectric constant). In toluene the molecular weight as well as the rate is strongly depressed indicating the preponderance of a chain breaking mechanism involving this solvent.
Anionic block polymerization. II. Preparation and properties of block copolymers
Authors: Baer M. 
Published: April 2003

AbstractBlock copolymers were prepared by anionic polymerization and their dynamic mechanical properties and thermal stability were compared with those of random copolymers and mechanical blends of similar composition. The block copolymers were prepared by means of Na‐naphthalene as the initiator, under conditions leading in most cases to almost complete absence of contaminating homopolymers. The composition, structure, and molecular weight of the block copolymers were determined by (a) molecular weight determinations of the polymers before and after addition of the second monomer to the preformed polymeric anions, and (b) by fractionation and chemical analysis of the resulting fractions. The block copolymers prepared were of the type: poly(α‐methyl styrene) ‐ polystyrene ‐ poly(α‐methylstyrene), polystyrene ‐ poly(α‐methylstyrene)‐polystyrene, poly(methyl methacrylate)‐polystyrene‐poly(α‐methyl methacrylate), and poly(ethylene oxide)‐polystyrene‐poly(ethylene oxide). The various block copolymer systems showed considerable differences in dynamic mechanical properties among themselves; they also had properties differing from those of copolymers and blends.
Infrared studies of conformational changes in polyvinyl chloride
Authors: Krimm S. , Enomoto S. 
Published: April 2003

AbstractAnalysis of the infrared spectrum of polyvinyl chloride has permitted the identification, from the frequencies of the several CCl stretching bands, of the chain conformations which are associated with particular chlorine pair configurations. These results have made it possible to establish that changes in conformational structure accompany certain changes in physical state of the polymer. Possible interpretations of the origins of these structural changes are considered.
Effect of film thickness upon the sorption of organic vapors in polymers slightly above their glass transition temperatures
Authors: Kishimoto A. , Matsumoto K. 
Published: April 2003

AbstractAbsorption and desorption of organic vapors in amorphous polymers in the temperature region slightly above Tg were studied as a function of film thickness. The systems chosen for this study were polyvinyl acetate (PVAc)–allyl chloride at 40°C. and polymethyl acrylate (PMA)–methyl acetate at 15 and 35°C. In PVAc studies reduced adsorption curves for different film thicknesses at relatively high equilibrium concentrations were apparently normal, but the initial slopes of the plots increased with increasing film thickness X and appeared to approach certain limiting values at the limit of infinite X. At lower equilibrium concentration two‐stage absorption curves appeared, and the variation of absorption curve with film thickness was too complicated to be interpreted in terms of the theory proposed by Crank and Long and Richman. The desorption curve was at all concentrations studied, almost normal and the initial slopes increased with increasing X. By assuming that the hypothetical sorption curve with the initial slope extrapolated to infinite X is controlled by a purely Fickian diffusion mechanism, we calculated the mutual diffusion coefficient D for this system and compared it with that derived by Meares from steady‐state permeation measurements. Both results agreed quite well, suggesting that the method presented here is effective for obtaining D. Absorption and desorption of methyl acetate by PMA at 15°C. were entirely similar to those obtained by PVAc in the corresponding region of equilibrium concentration. At 35°C. reduced sorption curves were independent of X and were purely Fickian. Following the analysis in PVAc, we predicted D for PMA at 15°C. as a function of methyl acetate concentration.
Polymer degradation. I. Column elution fractionation and thermal degradation of polyoxypropylene glycol–toluene diisocyanate (PPG‐TDI) polymers
Authors: Rapp Neville Sue , Ingham John D. 
Published: April 2003

AbstractA procedure has been worked out for the column elution fractionation of polyoxypropylene glycol–toluene diisocyanate (PPG‐TDI) polymers of molecular weight ∼100,000; by decreasing the column temperature from 34 to 7°C. the method was extended to degraded polymer of molecular weight ∼25,000. Graphical differentiation of the integral curves was eliminated by using Tung's empirical equations. The results for both degraded and undegraded polymer agreed with the theoretical most probable distributions; therefore, a random scission process of degradation is indicated.
Synthesis of crystalline polyvinylcyclobutane and polyvinylcycloheptane
Authors: Overberger C. G. , Kaye H. , Walsh G. 
Published: April 2003

AbstractThe synthesis of vinylcyclobutane and vinylcycloheptane is described. These compounds were polymerized to crystalline polyvinylcyclobutane and polyvinylcycloheptane with a triisobutyl aluminum–titanium tetrachloride catalyst system.
Mechanism of film formation from latices. Phenomenon of flocculation
Authors: Hwa Jesse C. H. 
Published: April 2003

AbstractThe mechanism of film formation was studied with respect to the flocculation phenomenon. It was observed that almost all latices would air‐dry to a point at which coagulation of the latex particles had just occurred and beyond which the wet film was no longer redispersible in water. This flocculation point was sharp and could be detected visually or by immersing the film in water. Two methods have been devised to measure the solids at which incipient flocculation occurred: cross‐section method, and cone method. The floc point was found to be about 50–60% for a model acrylic latex depending on the soap present in the dispersion. After flocculation had occurred, further drying would lead to different film properties depending on the hardness of the particles, the rate of drying, the substrate, and the degree of crosslinking.
Polymer–solvent interaction parameters and creep behavior of ethylene–propylene rubbers
Authors: Dudek T. J. , Bueche F. 
Published: April 2003

AbstractThe polymer–solvent interaction parameter for an ethylene–propylene terpolymer containing 53 mole‐% ethylene was determined as a function of degree of crosslinking in n‐heptane and benzene. A well characterized EPR gum vulcanizate was used to obtain the polymer–solvent interaction parameter in fourteen solvents, and the cohesive energy density of the terpolymer was evaluated. The composite tensile creep curves for gum and filled EPR vulcanizates were obtained and compared with SBR creep curves.
Some factors affecting the molecular association of poly(ethylene oxide) and poly(acrylic acid) in aqueous solution
Authors: Bailey F. E. , Lundberg R. D. , Callard R. W. 
Published: April 2003

AbstractInvestigations of the properties of very high molecular weight polymers of ethylene oxide have shown that, while this polymer structure is relatively nonpolar, it displays a high degree of polymer solvent interaction in aqueous systems. A unique application of the hydrogen bonding affinity of the ether oxygens in the poly(ethylene oxide) chain has been found in the molecular association complexes formed between this polyether and polymeric acids such as poly(acrylic acid). Interest in the properties of these complexes has prompted a more detailed study of the mechanism of association which occurs in solution. In this study the effects of pH, of composition and concentration, and of temperature on solution viscosity are examined in order to define the stoichiometry of the intermolecular association. A wide range of polymer molecular weights has been studied, ranging in the case of poly(ethylene oxide) from low molecular weight waxes to very high molecular weight polymers. The molecular complex of poly(ethylene oxide) and poly(acrylic acid) appears to be an association between ether oxygens and carboxyl groups through hydrogen bonding which approaches 1:1 stoichiometry. While at low pH this association is sufficient to cause phase separation, at higher pH the complex exists in solution. In neutral solution there also appears to be an interaction between the two polymer species.
Compositions in equilibrium two phases of polymer–solvent mixture systems
Authors: Yoshino Tsuneo , Fujisawa Kenji 
Published: April 2003

AbstractThe compositions in equilibrium two‐liquid phases of polymer–solvent mixture systems have been studied from the standpoint of preferential adsorption of one solvent component by measuring φout, νv, and V/m for toluene–isobutanol–polystyrene systems. Here φout is the volume fraction of toluene in the solvent mixture outside the adsorbed regions surrounding polymer molecules; ν′ is the volume of hypothetical toluene layers per unit weight of polymer substance, when the adsorbed regions are divided into pure toluene layers and the remaining parts with solvent composition equal to φout, keeping the amount of toluene in the adsorbed regions unchanged; and V/m is the volume of solvent per unit weight of polymer substance. ν′ is observed to be equal for both the polymer‐poor and polymer‐rich phases and independent of polymer concentration, so far as the polymer concentration in the latter phase is smaller than 0.2 g./cc. solvent, φout is found to be also equal for the both phases. These observations show that the ternary system at a temperature is approximated by a binary system consisting of polymer molecules which are composed of true polymer molecules and the toluene layers surrounding them, and solvent mixture outside the toluene layers. When V/m and ν′ in the polymer‐rich phase are plotted against decreasing φout, ν′ begins to decrease at φout = 0.6, where the change of V/m along a steep curve for φout > 0.6 is slowed down. This suggests that after the polymer‐rich phase is deprived of most of the solvent outside the adsorbed regions the adsorbed regions begin to lose solvent. The magnitude of the adsorbed regions per unit weight of polystyrene in a dilute solution with φout > 0.6 is estimated to be about 5 cc./g. from V/m of a polymer‐rich phase with φout = 0.6.
An interpretation of gaseous diffusion through polymers using fluctuation theory
Authors: DiBenedetto A. T. , Paul D. R. 
Published: April 2003

AbstractAn amorphous polymer is visualized as an ensemble of N independent, n‐center polymer segments. An ergodic hypothesis and a canonical ensemble are utilized in determining the probability of a given volume fluetuation within the polymer. The thermal energy change associated with a given volume fluctuation is calculated and related to the activation energy for gaseous diffusion. Polymer segment lengths were in the range of 6–20 A. and appeared to decrease with increasing temperature in the case of natural rubber. The results were interpreted to show that the activation energy for gaseous diffusion in rubbery polymers went into the breaking of cohesive bonds between parallel polymer segments while in glassy polymers it went into both the breaking of cohesive bonds and the compressing of the surrounding segments. It is felt that it may be possible to relate gaseous diffusion, self‐diffusion, and viscous flow to the thermodynamic and molecular properties of an amorphous polymer.
Evaluation of molecular weight averages resulting from random chain scission process for wide distributions as in polyolefins
Authors: Kotliar A. M. 
Published: April 2003

AbstractThe effects of random degradation on the molecular weight averages for broad Schulz‐Zimm and Wesslau type distributions are evaluated by blending two most probable Flory type distributions so that the Mn:Mw:Mz ratios of the blend were equal to that of the distribution models for any particular Mw/Mn ratio. The results indicate a rather extreme sensitivity of broad Wesslau distributions to small degrees of degradation and suggest that this function is not a good description for polyolefins.
Polymerization of butyl esters of methacrylic acid and hydrolysis of the polymers
Authors: Matsuzaki Kei , Okamoto Takehiko , Ishida Akira , Sobue Hiroshi 
Published: April 2003

Abstracttert‐Butyl methacrylate was polymerized with Grignard reagent, benzoyl peroxide, and gamma rays as initiator. The infrared spectra of the polymers indicated that the polymer polymerized with Grignard reagent had an isotactic stsucture and those polymerized with benzoyl peroxide and gamma rays had syndiotactic structures. Hydrolysis of polymethyl methacrylates and poly‐tert‐butyl methacrylates with hydroiodic acid was attempted, and differences in the infrared spectra of the polymethacrylic acids obtained due to stereoregularity were discussed. No difference in the demethylation behavior due to stereoregularity of polymethyl methacrylates was observed. Heat treatment of polymethacrylic acids and poly‐tert‐butyl methacrylates showed that isotactic polymers form polymer anhydride faster than syndiotactic polymers.
Molecular weight distributions in equilibrium polymerizations
Authors: Lundberg J. L. 
Published: April 2003

AbstractMolecular weight distributions at polymerization equilibria appear to fall between two limiting cases, one which gives a “most probable” distribution and one which gives a very broad distribution. The difference between the two results depends on whether entropies of pure, crystalline homopolymers or pure, unoriented liquid homopolymers are proportional to molecular size. The free energies of polymerization of liquid homopolymers of ethylene can be estimated from published thermodynamic data if the entropies of pure, disoriented, liquid homopolymers are assumed to be proportional to molecular size. This leads to the expectation that molecular weight distributions are very broad for equilibrium polymers. For polyethylenes at polymerization equilibria, weight‐average/number‐average degree of polymerization ratios of 6 to 33, high weight‐average degrees of polymerization (102 ≤ nw ≥ 1014), and equilibrium monomer fugacities from 10−10 to 102 atm. are predicted at temperatures of 300–600°K. and at total pressures in the 1–104 atm. range. These results are consistent with molecular weights and molecular weight distributions found for nonequilibrium polyethylenes. This agreement indicates that ethylene polymerizations might be controlled in part by energetics and not by kinetics alone.
Aromatic polyhydrazides: A new class of highly bonded, stiff polymers
Authors: Frazer A. H. , Wallenberger F. T. 
Published: April 2003

AbstractHigh‐molecular weight aromatic polyhydrazides have been prepared by using isophthalic, terephthalic, isocinchomeronic, dipicolinic, 5‐chloroisophthalic, 2,5‐dichloroterephthalic, 5‐tert‐butylisophthalic, phenyl ether‐4,4′‐dicarboxylic, pyrazine‐2,5‐dicarboxylic, and thiophene‐2,5‐dicarboxylic acid as polymer intermediates. The polyhydrazides were prepared from equimolar amounts of diacid chloride and dihydrazide (or hydrazine) in hexamethylphosphoramide at room temperature. By contrast to aliphatic polyhydrazides, aromatic polyhydrazides were soluble in dimethyl sulfoxide and with few exceptions had polymer melt temperatures in the range of 350–400°C. Inherent viscosities ranged from 0.30 to 1.00 (in dimethyl sulfoxide). Tough films and strong fibers of these polymers could be fabricated.
Thiaalkyl polyacrylates: The influence of sulfur in the side chain
Authors: McCurdy Richard M. , Prager Julianne H. 
Published: April 2003

AbstractA series of acrylic esters containing a thio ether atom in the side chain has been prepared and polymerized. The glass transition temperatures and swelling volumes are reported as follows: 3‐thiabutyl polyacrylate, Tg −60°C., 9% volume swell in 70:30 isooctane‐toluene; 3‐thiapentyl polyacrylate, −71°C., 31% 4‐thiapentyl polyacrylate, −65°C., 32% 4‐thiahexyl polyacrylate, −76°C., 36% 5‐thiahexyl polyacrylate, −70°C., 36%. These data are compared with those for certain other polyacrylates; the relation between the structure and the properties of these materials is discussed.