bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of initiation in the γ‐radiation‐induced polymerization of ethylene
Authors: Mitsui Hiroshi , Machi Sueo , Hagiwara Miyuki , Kagiya Tsutomu 
Published: April 2003

AbstractThe relation between the gaseous products and the reaction conditions such as pressure, temperature, and dose rate in the γ‐radiation‐induced polymerization of ethylene was studied. The main gaseous products were hydrogen and acetylene, and the amounts of these products increased linearly with reaction time, monomer density, and dose rate, while they were independent of reaction temperature. The ratio of rate of formation of hydrogen to acetylene was about one‐half. Further, it was found that the number of moles of polymer chain formed was almost equal to that of acetylene at room temperature. An initiation mechanism in which both hydrogen and acetylene are formed is proposed. The equation which is derived on the basis of the initiation mechanism is shown to be in good accordance with the experimental results.
Applications of limiting conversion free‐radical polymerizations. I. tert‐butyl hydroperoxide‐initiated polymerization of styrene in benzene
Authors: Indictor N. , Linder C. 
Published: April 2003

AbstractData for the tert‐butyl hydroperoxide‐initiated polymerization of styrene in dilute benzene solution at 126°C. are presented. These data are discussed in terms of Tobolsky's limiting conversion kinetics. Several rate laws are considered. Simple unimolecular decomposition of the peroxide appears to be unimportant under these conditions, as does solvent interaction.
Studies on poly(vinyl chloride). III. The role of the precipitated polymer in the kinetics of polymerization of vinyl chloride
Authors: Cotman John D. , Gonzalez Margaret F. , Claver George C. 
Published: April 2003

AbstractIn polymerization of vinyl chloride monomer, free radicals precipitate on or within aggregates of partially swollen dead polymer. Polymerization on the solid polymer is characterized by autoaccelerating rates due to a progressive reduction in termination rate. This reduction in termination rate is due to the fact that as the reaction progresses and more polymer accumulates there is a decrease in probability that chain transfer of polymer radicals to monomer will generate a mobile radical, which can readily terminate an occluded or stuck free radical. From the appearance of the particles of solid polymer in the system, it has been concluded that free radicals precipitate both on polymer particle surface and inside the open structure of polymer particles.
Linear polymers of vinyl aryl monomers containing another unsaturated group
Authors: D'Alelio G. F. , Hoffend T. R. 
Published: April 2003

AbstractThe synthesis and the anionic polymerization of representative substituted styrenes, CH2CHC6H4R′, where R′ is an ethylenic or acetylenic group attached directly or indirectly to the benzene ring, to linear polymers is described. In contrast, crosslinked polymers were obtained when radical and cationic initiators were used. The unpolymerized, unsaturated bonds in R′ in the resulting linear polymers were shown to be present by infrared spectroscopic methods and by the following post‐reactions of these bonds: (1) the thermal‐ and radical‐initiated crosslinking of the linear polymers through the unsaturated bonds in R′; (2) the post‐bromination of these unsaturated bonds; (3) the post‐copolymerization of these unsaturated bonds with vinyl monomers; and (4) the reaction of decaborane with the acetylenic bonds. The anionic copolymerizations of methyl methacrylate, acrylonitrile, and styrene with these monomers were performed and confirmed their behavior as substituted styrenes. Block copolymerizations with styrene and methyl methacrylate were also performed and the expected results obtained. Post‐bromination of the linear polymers afforded self‐extinguishing polymers. The linear polymers and copolymers may be classified as “self‐reactive” polymers which yield thermosetting polystyrenes.
Preparation and characterization of some cellulose graft copolymers. Part IV. Some properties of isolated cellulose acetate–styrene graft copolymers
Authors: Wellons J. D. , Williams J. L. , Stannett V. 
Published: April 2003

AbstractA series of purified graft copolymers of cellulose acetate and polystyrene, which were prepared and characterized during the course of an earlier investigation, have been used for some initial property studies. Grafts with high molecular weight backbones and low molecular weight side chains and vice versa, and with both side chains and backbones of high and low molecular weights, were prepared. The graft polymers were found to be insoluble in most solvents but soluble in dimethylformamide and pyridine and in mixtures of solvents for each component. Films cast from mixtures of the grafts and homopolymers showed that the grafts were compatible with the homopolymer of the component with a higher molecular weight. A graft copolymer with high molecular weight backbone and side chains was found to be compatible with both homopolymers separately and with a mixture of both across a wide range of compositions. A blend of the high and low molecular weight grafts was also found to be highly compatible with both homopolymers. The permeability, diffusion, and sorption of gases and water vapor in the grafts and in the corresponding homopolymers was also studied. In the case of water vapor, the sorption in cellulose acetate was much higher than in polystyrene whereas the diffusion was much lower. It was found that the graft polymers showed both diffusion and solution behavior closer to that of cellulose acetate, whereas the permeability constants were more intermediate between those of the two homopolymers. The gas permeability and diffusion constants were found to be intermediate between the values obtained with the two homopolymers.
Polymerization of methyl methacrylate with butyllithium–diethylzinc complex
Authors: L'Abbe G. , Smets G. 
Published: April 2003

AbstractThe low‐temperature polymerization of methyl methacrylate initiated with butyllithium–diethylzinc has been studied in toluene and in toluene–tetrahydrofuran and toluene–dioxane mixtures in various proportions. The polymerization process is typically anionic; it is characterized by a very rapid initiation reaction, and the absence of termination and chain transfer reactions, the molecular weight increasing proportionally with the degree of conversion. With toluene as a solvent, the polymer chains are associated, as is shown by viscometric measurements; moreover the polymers produced are highly polydisperse (Mv/Mn = 5.4). The kinetics are very complicated and vary with the range of the catalyst and monomer concentrations. In pure toluene in the presence of the organometallic complex, butyllithium–diethylzinc, the monomer addition is more stereospecific than when butyllithium alone is used as catalyst. By adding tetrahydrofuran to the reaction mixture, the polymer chain association disappears; concomitantly the stereochemical structure of the polymer changes from an isotactic to a mainly syndiotactic configuration. In toluene–tetrahydrofuran mixtures containing from 1 to 10 vol.‐% tetrahydrofuran, the kinetics of polymerization can easily be interpreted by assuming the presence of two propagating reactive species which are in equilibrium with each other: the ion pair and the THF‐solvated ion pair. The energy of activation of propagation for the free ion pair is equal to 7.5 kcal./mole; for the solvated ion pair a value of 5.5 kcal./mole was found, including the solvation enthalpy of the organometal with tetrahydrofuran. The existence of any relation between the reactivity of the propagating species and the tactic incorporation of the monomeric units has been discussed. The polymerization in mixtures of toluene–dioxane is intermediate between that in pure toluene and that in toluene–HF mixtures; the reaction mechanism however cannot be interpreted with the usual kinetic scheme. The experimental data concerning the rate dependence on catalyst and monomer concentrations are briefly summarized.
Method of calibrating gel permeation chromatography with whole polymers
Authors: Cantow Manfred J. R. , Porter Roger S. , Johnson Julian F. 
Published: April 2003

AbstractColumn systems for gel permeation chromatography are usually calibrated by eluting a series of sharp polymer fractions of known molecular weights and by correlating their elution volumes with molecular size or weight. A different method for calibration is proposed in which only one polymer sample, with a broad, well‐characterized molecular weight distribution, is used. The cumulative distribution and the integrated, normalized GPC chromatogram are successively superimposed, and molecular weights and corresponding elution volumes are correlated. It is found that calibration curves obtained in this manner show a definite curvature. A possible explanation and correction for this behavior is given, based on the concentration dependence of elution volumes.
High‐resolution NMR of crosslinked polymers: Effects of crosslinked density and solvent interaction
Authors: Liu Kang‐Jen , Burlant William 
Published: April 2003

AbstractMeasurements have been made of the dependence of nuclear magnetic resonance bandwidths of polymers on the degree of crosslinking. Poly(methyl methacrylates) and poly(hexadecyl acrylates) were studied. Three regions of behavior are apparent: (1) in lightly crosslinked materials, bandwidths are quite insensitive to the degree of crosslinking, and the networks behave almost as linear polymers in solution; (2) in moderately crosslinked material, bandwidths are significantly affected by the degree of crosslinking; and (3) in highly crosslinked materials, bandwidths are extremely sensitive to crosslink density, and the polymer peaks become so broad that they disappear almost completely. These results indicate that segmental motion of a polymer in solution is not a function solely of its molecular weight, and that a certain degree of crosslinking is required to restrict polymer motion at the segmental level. The solvent (benzene) peak is always a singlet in swollen poly(methyl methacrylate) systems with swelling ratios up to 6.4 (regions 1 and 2, above) but as the swelling ratio further decreases to 3.5 (region 3), the solvent peak splits into a doublet; this phenomenon may indicate the existence of two different arrangements of solvent molecules in the swollen network, for which interchange is not sufficiently rapid to produce a single line.
Cyclocopolymerization of dicyclic dienes and maleic anhydride to fused ring systems
Authors: Meyersen Klaus , Wang Jean Y. C. 
Published: April 2003

AbstractThe cyclocopolymerization of maleic anhydride and four 1,5‐ and 1,6‐dienes (bicyclopentene, bicyclohexene, dicyclopentenyl ether, and dicyclohexenyl ether) and one tetraene (quartercyclopentene) is described. Soluble, low molecular weight copolymers were obtained from all five compounds. Their compositions approach 2:1 copolymer ratios. Fused ring structures are proposed as the main repeating units. Among the compounds listed, bicyclopentene copolymerized most easily and gave good conversions for monomer ratios of 2:1. Quartercyclopentene and dicyclopentyl ether, the other five‐membered ring compounds, also polymerized to good‐to‐fair yields. However, a monomer ratio of about 4:1 was required to obtain conversions comparable to a 2:1 maleic anhydride—bicyclopentene polymerization. The six‐membered systems, bicyclopentene and dicyclopentenyl ether, gave consistently low conversions, even with a 4:1 monomer ratio. The influence of the initiator system, initiator concentration, and reaction medium was studied on copolymerizations of bicyclopentene. Best results were obtained in acetic anhydride with azobisisobutyronitrile as the initiator.
Polyoxazolidones
Authors: Iwakura Yoshio , Nabeya Aiko , Hayano Fusakazu , Kurita Keisuke 
Published: April 2003

AbstractPolyurethans with chloromethyl side chains were prepared by the polyaddition reaction of bischlorohydrins and diisocyanates. The polyurethans had inherent viscosities in a range of 0.22–0.60 and gave transparent films by solution casting. These polyurethans were easily converted to the polyoxazolidones by treatment with sodium methoxide. The polyoxazolidones had inherent viscosities up to 0.51, and gave transparent films by solution casting.
Effects of metal salts on polymerization. Part IV. Polymerization of N‐vinylcarbazole initiated by oxidizing metal nitrates
Authors: Tazuke Shigeo , Tjoa Tjin Bu , Okamura Seizo 
Published: April 2003

AbstractThe polymerization of N‐vinylcarbazole (VCZ) in ethylene dichloride, acetone, benzene, and dioxane with cupric nitrate, ferric nitrate, and ceric ammonium nitrate as catalyst was studied. In all cases the polymerization seemed to be of a cationic nature, judged by copolymerization with styrene. Electron spin resonance (ESR) spectroscopy was made for the polymerization system and also for a system containing N‐ethylcarbazole instead of VCZ. Singlet ESR spectra were observed for all systems containing ceric salt and for some systems containing ferric salt but not for systems containing cupric salt. The ESR spectra indicated the formation of an ion radical by electron transfer between the oxidizing metal salt and the carbazole derivatives. Mechanisms of initiation other than electron transfer were less likely, and it was concluded that the initiation process was most likely to be of the electron transfer type.
Copolymerization of trioxane with styrene catalyzed by BF3·O(C2H5)2
Authors: Higashimura T. , Tanaka A. , Miki T. , Okamura S. 
Published: April 2003

AbstractIt was determined whether trioxane, a cyclic formal, can copolymerize with styrene, a vinyl monomer, in the presence of BF3·O(C2H5)2 catalyst at 30°C. The methanol‐in‐soluble fraction after extraction with benzene was found to contain the copolymer of styrene and trioxane, thus demonstrating that trioxane can copolymerize with styrene In this case the amount of the methanol‐insoluble polymer was less than that of the total monomer consumed, as determined by gas chromatography. This was found to be caused partly by the formation of the cyclic oligomer, 4‐phenyl‐1,3‐dioxane. The relative reactivity of styrene was qualitatively found to be larger than that of trioxane, not only from the rate of monomer consumption but also from the composition of the methanol‐insoluble polymer obtained. In a nonpolar solvent the reactivity of trioxane increased, and the difference in reactivity between the two monomers decreased. Indeed, an apparent monomer reactivity ratio might be obtained from the relationship between the monomer composition and the monomer consumption rate or the composition of the methanol‐insoluble polymer, but it did not have a quantitative meaning because of the complexity of the copolymerization reaction.
Synthesis of 5(6)‐vinylbenzimidazole and of 2‐vinylbenzimidazole
Authors: Overberger C. G. , Kösters B. , St. Pierre T. 
Published: April 2003

AbstractThe syntheses of 2‐ and 5(6)‐vinylbenzimidazole are described. These compounds were characterized by appropriate chemical reactions and physical properties. Incidental to this work, 3,4‐diaminostyrene was also prepared.
Analysis of polyethylenimine by spectrophotometry of its copper chelate
Authors: Perrine T. D. , Landis W. R. 
Published: April 2003

AbstractPolyethylenimine (PEI) forms a copper chelate with a N/Cu ratio of about 5 and with extinction coefficients of about 175 at 6350 A. and 4250 at 2694 A. Solutions of PEI‐copper chelate obey Lambert's and Beer's laws and show increased optical density in the presence of chloride ion. Above pH 4.25, hydrogen ion has little effect. A comparison with the copper chelate of polyvinylamine suggests that PEI has a highly, branched structure. Analysis of PEI via its copper chelate is described.
Preparation and polymerization of a sugar dithiol
Authors: Whistler Roy L. , Hoffman Daniel J. 
Published: April 2003

Abstract2,4‐O‐Benzylidene‐1,6‐dithiol‐D‐glucitol is prepared by nucleophilic displacement of tosyloxy groups from 3,5‐di‐O‐acetyl‐2,4‐O‐benzylidene‐1,6‐di‐O‐tosyl‐D‐glucitol with thioacetate in N,N‐dimethylformamide and deacetylation of the product. Oxidative polymerization with oxygen and selenium dioxide produces film‐forming disulfide polymers with intrinsic viscosities up to 0.41. Other oxidizing agents produce polymers of lower viscosity. Condensation of the dithiol with benzaldehyde also gives polymers of low viscosity.
On the thermal behavior of 4‐(o‐carboranyl)‐1‐butylmethyl siloxane–dimethyl siloxane copolymers
Authors: Delman A. D. , Kelly J. J. , Stein A. A. , Simms B. B. 
Published: April 2003

AbstractPolysiloxanes containing carboranylbutyl and methyl pendant groups were investigated, to determine their resistance to thermal decomposition when heated in air. Results indicate that the copolymers degrade through SiC as well as SiO bond rupture. At 300°C. thermooxidative scission of pendant groups was the predominant reaction. whereas SiO and SiC bond rupture occurred at 500°C. Variations in the behavior of the copolymers studied suggest that the carborane nucleus provides some inhibiting influence on their thermal decomposition. This is mainly attributed to steric hindrance effects rather than polarity factors. Chain extension with tin octoate caused a reduction of thermal stability, probably because of the addition of SnO bonds to the molecules.
Acid‐catalyzed methanolysis of tri‐O‐methylamylose and tri‐O‐methylcellulose
Authors: BeMiller J. N. , Allen Earle E. 
Published: April 2003

AbstractPast experimental evidence has indicated that the acid‐catalyzed hydrolysis of polysaccharides does not proceed randomly, and it has been suggested that hydrolysis is more rapid for the glycosidic bonds by which the nonreducing endgroups are attached. To test this hypothesis, amylose and cellulose were permethylated and subjected to methanolysis. It was found that in both the methanolysis of tri‐O‐methylamylose and tri‐O‐methylcellulose the production of methyl 2,3,4,6‐tetra‐O‐methyl‐α,β‐D‐glucopyranoside was complete before the production of methyl 2,3,6‐tri‐O‐methyl‐α,β‐D‐glucoside was finished. Since the former compound could only come from the original nonreducing end units and the latter from all other units, these results were interpreted as giving support to the idea of a preferential scission of the bonds at the nonreducing ends, even though the release of original end units was not complete until 70–85% of the glycosidic bonds had been cleaved. It was concluded that methanolysis proceeds by a modification of the hydrolysis mechanism and that methanolysis is therefore a poor model for hydrolysis.
Differential permeation and absorption of water vapor in polyacrylamide film
Authors: Kishimoto Akira , Kitahara Takeru 
Published: April 2003

AbstractAn investigation has been made of successive differential absorption and differential permeation of water vapor in polyacrylamide a t 30°C. The successive differential ab sorptions showed two types of non‐Fickian anomalies: sigmoid type and two‐stage type curves. The experimental data have been analyzed in terms of the Fick diffusion equation assuming a time‐dependent approach of the surface concentration. The calculated family of absorption curves agreed with the experimental results. The permeation curves in the region of high and low pressure increments were apparently normal, but at medium pressures they showed anomalous behavior. It was found that in the differential type of permeation experiment the stress effect induced by a concentration gradient between the surfaces of the film was eliminated. By assuming the time‐dependent approach of the equilibrium surface concentration, we calculated the time lag as a function of film thickness and applied the theory to the data for permeation through polyacrylamide film with different film thicknesses a t relatively small pressure intervals. The rate parameter calculated from permeation data was found to be in good agreement with that from successive differential absorption data.
Stereoregularity of poly(methyl acrylate)
Authors: Matsuzaki Kei , Uryu Toshiyuki , Ishida Akira , Ohki Tatsumi , Takeuchi Makoto 
Published: April 2003

AbstractThe stereoregularity of poly(methyl acrylate) and poly(methyl acrylate‐αd) was determined from the NMR spectra. A method of quantitative determination of stereoregularity of poly(methyl acrylate) proposed in this paper is based on the fact that in the 100 Mc./sec. NMR spectrum the absorption peaks due to methylene protons in syndiotactic configurations overlap absorptions due to only one of two methylene protons in isotactic configurations. The stereostructure of poly(methy1 acrylates) polymerized with anionic catalysts such as Grignard reagents, n‐butyllithium, and LiAlH4 is generally richer in isotactic diads than in syndiotactic diads. For example, poly(methyl acrylate) polymerized with phenylmagnesium bromide as catalyst at −20°C. consists of 99% isotactic and 1% syndiotactic diads. In radical polymerization, the isotacticity of poly(methyl acrylate) is independent of polymerization temperature. Poly(methyl acrylates) polymerized with a Ziegler‐Natta catalyst consisting of Al(C2H5)2Cl and VCl4 have configurations similar to those polymerized by radical initiators. The stereoregularity of poly(methyl acrylate‐α‐d) resembled that of poly(methyl acrylate) polymerized under the same conditions.
Polyethers. I. Polymerization of 2‐methyl‐2‐butene oxide
Authors: Field N. D. , Kieras J. A. , Borcherts A. E. 
Published: April 2003

Abstract2‐Methyl‐2‐butene oxide (2,3‐epoxy‐2‐methylbutane) was polymerized with modified alkylaluminum initiators a t low temperatures to a high‐melting, crystalline, film‐forming polymer. High yields and comparatively high molecular weights were obtained with Al(i‐Bu)3−xH2O initiators in inert diluents. When such initiators were modified with acetylacetone they became ineffective. Ammonia could be substituted for water in formulating an active initiator. Attempts to prepare an active initiator in the presence of the monomer were unsuccessful indicsting competition with the water for Al(i‐Bu)3. Thermal decomposition of the polymer produced methyl isopropyl ketone with some pivaldehyde.
Mechanism of thermal stabilizers for poly(vinyl chloride). II. Synergistic effect of combination of metal soaps
Authors: Onozuka Mitsuo 
Published: April 2003

AbstractThe esterification of metal soaps, in the combination of zinc and calcium soaps, on poly(vinyl chloride) (PVC) has been carried out both in liquid and solid phase to determine why the reactivity of zinc soap decreases on addition of calcium soap, improving the long‐run heat stability of PVC and causing the well‐known synergism. It is suggested as the mechanism of synergism that metal soaps having low ionization‐potential values, such as calcium soap, act as ester‐exchangers of metal chlorides, such as zinc chloride, which is generated after the stabilization of PVC, and also decrease the reactivity of the zinc soap by forming a complex, as that of zinc soap—calcium soap. If a third material, such as organic ester silane, reacting as ester‐exchanger on zinc chloride and preventing the formation of a zinc—calcium soap complex, is added to the system, these compounds have an excellent synergistic effect.
Aromatic polyhydantoins from bisiminoacetate and diiscyanates
Authors: Imai Yoshio 
Published: April 2003

AbstractAromatic polyhydantoins of high molecular weight have been prepared by a polyaddition—cyclocondensation reaction of diethyl m‐phenylenebisiminoacetate with aromatic diisocyanates in m‐cresol. The polyhydantoin obtained from methylenebis(4‐phenyl isocyanate) showed good thermal stability up to 400°C. in air. A transparent and tough film could be cast from a m‐cresol solution of the polymer.