bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization in the crystalline state. X. Solid‐state conversion of 6‐aminocaproic acid to oriented nylon 6
Authors: Macchi E. M. , Morosoff N. , Morawetz H. 
Published: April 2003

AbstractWhen single crystals of 6‐aminocaproic acid (ACA) are heated about 30°C below their melting point, polycondensation to nylon 6 takes place. The polymer crystallites are biaxially oriented towards each other and the relation between their orientation and that of the parent monomer crystal has been clarified. The kinetics of the process are characterized by three stages, (a) an induction period, (b) a stage in which monomer disappears at a constant rate while polymer of relatively low molecular weight is formed, and (c) a slow polycondensation of the polyamide chains after exhaustion of the monomer. Oligomer concentrations were below detectable limits at all stages of the process. Addition of monomer to the polyamide was retarded when ACA was kept from reaching its equilibrium vapor pressure (0.12 mm Hg at 170°C) by condensation on a cool surface or when an inert gas was admitted to the system. This was interpreted as suggesting that ACA is transported through the vapor phase to the propagating polyamide. A number of surfaces catalyzed the polycondensation of ACA vapor, but nylon 6 formed in this way on KCl crystals exhibited no preferred orientation. The linear dimer and trimer of ACA were also found to condense to nylon 6 in the crystalline state, although at a slower rate than the monomer. The solid‐state polycondensation of these oligomers was accelerated when they were exposed to the vapor of the monomer. Solid‐state polycondensation of single crystals of the linear dimer led also to biaxially oriented nylon 6.
Thermal reactions of polyacrylonitrile
Authors: Hay J. N. 
Published: April 2003

AbstractThe exothermic process which occurs on heating polyacrylonitrile above 200°C. is studied with a differential scanning calorimeter and by following volatiles production. The process is associated with coloration of the polymer and the production of ammonia. It is not due to chain scission degradation, which occurs in this temperature range and also produces volatiles.
Polymerization of α‐amino acid N‐carboxy anhydrides. III. Mechanism of polymerization of L‐ and DL‐alanine NCA in acetonitrile
Authors: Iwakura Yoshio , Uno Kiekichi , Oya Masanao 
Published: April 2003

AbstractThe polymerization of L‐ and DL‐alanine NCA initiated with n‐butylamine was carried out in acetonitrile which is a nonsolvent for polypeptide. The initiation reaction was completed within 60 min.; there was about 10% of conversion of monomer. The number‐average degree of polymerization of the polymer obtained increased with the reaction period, and it was found to agree with value of W/I, where W is the weight of the monomer consumed by the polymerization and I is the weight of the initiator used. The initiation reaction of the polymerization was concluded as an attack of n‐butylamine on the C5 carbonyl carbon of NCA. The initiation, was followed by a propagation reaction, in which there was attack by an amino endgroup of the polymer on the C5 carbonyl carbon of NCA. The rate of polymerization was observed by measuring the CO2 evolved, and the activation energy was estimated as follows: 6.66 kcal./mole above 30°C. and 1.83 kcal./mole below 30°C. for L‐alanine NCA; 15.43 kcal./mole above 30°C., 2.77 kcal./mole below 30°C. for DL‐alanine NCA. The activation entropy was about −43 cal./mole‐°K. above 30°C. and −59 cal./mole‐°K. below 30°C. for L‐alanine NCA; it was about −14 cal./mole‐°K. above 30°C. and −56 cal./mole‐°K. below 30°C. for DL‐alanine NCA. From the polymerization parameters, x‐ray diffraction diagrams, infrared spectra, and solubility in water of the polymer, the poly‐DL‐alanine obtained here at a low temperature was assumed to have a block copolymer structure rather than being a random copolymer of D‐ and L‐alanine.
Evidence for several species of active sites in Ziegler‐Natta catalysts
Authors: Lovering Edward G. , Wright William B. 
Published: April 2003

AbstractThe kinetics of isoprene polymerization catalyzed by VCl3 and Et3Al were studied by measuring fractional conversions, polymer composition, and molecular weight distributions at a series of reaction times and temperatures. The rate of polymerization plotted against temperature shows an inflection point with a minimum and maximum in the 60–90°C range. The isomeric composition of the polymer changes with temperature but not with reaction time, while the molecular weight distribution undergoes substantial change with both of these variables. The rate of polymerization at sites producing low molecular weight polymers was measured, and the activation energy calculated to be about 10 kcal/mole. The active sites were found to deactivate at different rates. The results support the hypothesis that several species of active sites are present in the system and that these exhibit characteristic polymerization behavior.
Reduction of disulfide bonds in keratin with 1,4‐dithiothreitol. I. Kinetic investigation
Authors: Weigmann Hans‐Dietrich 
Published: April 2003

AbstractThe kinetics of the reduction of disulfide groups in wool fibers with dithiothreitol has been investigated. The rate‐controlling process appears to depend on the pH of the reducing solution and changes from diffusion control to reaction rate control as the pH is decreased from neutral to pH 3.50. Pseudo second‐order kinetics, second‐order with respect to the concentration of the disulfide groups in keratin, has been found to describe the experimental data at pH 3.50. An activation energy of 25 kcal/mole has been determined for the rate‐controlling step at that pH value, as opposed to an activation energy of 13.4 kcal/mole for the diffusion‐controlled process at neutral pH. Only about 85% of the disulfide groups are accessible to dithiothreitol under the conditions which were investigated.
Grafting of monosaccharide derivatives to cellulose acetate
Authors: Whistler Roy L. , Ruffini Guglielmo , Pyler Richard E. 
Published: April 2003

AbstractGrafting of 1,2‐O‐isopropylidene‐α‐D‐xylofuranose to commercial cellulose diacetate has been accomplished by using a boron trifluoride catalyst. The reaction proceeds quickly at 25 and 40°C, resulting in degrees of molar substitution (MS) of 0.37 and 0.34, respectively. If monomer and catalyst are added over an extended period of time to maintain low concentrations, MS values as high as 0.89 and 0.85 are obtained at 25 and 40°C, respectively. Major side reactions are depolymerization of the cellulose acetate backbone and grafted D‐xylose and the homopolymerization of the monomer. These side reactions may be minimized by conducting the reaction at 40°C for a short time or by adding monomer and catalyst over an extended period of time. Grafting has also been accomplished by using D‐xylose derivatives with various reactive groups at the anomeric carbon atom. The grafted material of MS greater than 0.7 is insoluble in acetone and after deacetylation is soluble in water under alkaline, neutral and acidic conditions. Oxalic acid hydrolysis of the deacetylated material indicates that most of the grafted D‐xylose units are in the furanose form. Methylation and hydrolysis of the methylated material shows that 75% of the D‐xylose residues are terminal units and indicates the presence of many singly grafted D‐xylose residues and a few di‐and trisaccharide grafts.
Formaldehyde equilibria: Their effect on the kinetics of the reaction with phenol
Authors: Zavitsas Andreas A. 
Published: April 2003

AbstractThe kinetics of the base catalyzed hydroxymethylation of phenol by aqueous formaldehyde are influenced strongly by the equilibria among the hydrated forms of formaldehyde, and among the hydrates and the alcoholic function of the products. Apparent peculiarities in the kinetics of the system and seemingly anomalous solvent effects are shown to be due to erroneous formulation of the previously accepted rate expression. The correct expression is: Rate = k[Pi−] [F]m, where Pi− is phenoxide ion, F is unreacted formaldehyde, and m is the fraction of formaldehyde in the form of monomeric hydrate. Formaldehyde tied up in equilibria as αω‐poly(oxymethylene) diols, and hemiformals of the hydroxymethylphenols, constitutes a potential source of formaldehyde and is detected by the usual analytical procedures, but does not contribute to the rate of the hydroxymethylation reaction.
Autoxidation of polypropylene catalyzed by cobalt salt in the liquid phase
Authors: Kamiya Yoshio 
Published: April 2003

AbstractThe autoxidation of isotactic polypropylene suspended in the organic solvent was found to proceed very rapidly in the presence of cobalt salts. The rate of oxidation increases and the induction period decreases as the concentration of the cobalt is increased. The rate of oxidation depends on solvent and is quite fast in fatty acids. Polypropylene has shown a rapid decrease in molecular weight at the initial stage of oxidation, and the volatile products were mainly composed of carbon dioxide and small amount of carbon monoxide. Other oxidation products were acetic acid‐soluble resinous materials, having molecular weights of 250–730, with a molar ratio of carbon to oxygen of 3.0–5.4. Atactic polypropylene, relatively stable against oxidation, was oxidized easily in the presence of cobalt and bromide ion. The difference in the rate of oxidation depending on the tacticity of polypropylene is attributed primarily to steric hindrance to the intramolecular hydrogen abstraction step.
Polymerization of isocyanates. V. Thermal degradation of polyisocyanates
Authors: Iwakura Yoshio , Uno Keikichi , Kobayashi Norio 
Published: April 2003

AbstractThermal degradation of polyisocyanates was investigated. The only degradation products were monomer and trimer. The main product was trimer for most aliphatic polymers, and monomer for aromatic polymers. Poly(cyclohexyl isocyanate) gave only its monomer on account of steric requirements. The apparent activation energy was calculated for aromatic polymers by using TGA and DTA curves.
Polymerization of ethylene catalyzed by diethylaluminum chloride and titanium (III) acetylacetonate
Authors: Watt W. R. , Fry F. H. , Pobiner H. 
Published: April 2003

AbstractCatalysts for the polymerization of ethylene were prepared from titanium (III) acetylacetonate and diethylaluminum chloride. Titanium (III) acetylacetonate is of interest because it is soluble in hydrocarbon solvents used as polymerization media. As its oxidation product oxobisacetylacetonatotitanium (IV) is also hydrocarbon‐soluble, this system provides a vehicle for studying the effects of a change in valence on catalyst activity without an accompanying change of state, as occurs with titanium halides. Relatively high molar ratios (>20:1) of aluminum alkyl to titanium compound were required to give active catalysts. Precipitates generally formed in the catalyst mixtures, although dilute catalyst solutions in which no precipitate was visible still initiated polymerization. Catalyst mixtures were observed to undergo certain changes on standing. Light‐scattering studies indicated an increase in catalyst particle size, and a gas identified as ethane was evolved. These changes were accompanied by a reduction in activity of the catalyst. Parallel polymerization tests were run for a comparison of catalysts prepared from titanium(III) acetylacetonate and catalysts prepared from oxobisacetylacetonatotitanium(IV). There was essentially no difference in yield or properties of polymer prepared using the two catalyst systems. The evidence suggests that both the trivalent and tetravalent titanium compounds yield the same catalytic intermediate when reacting with diethylaluminum chloride.
The structure and transport properties of poly(methacrylic acid) in aqueous solution
Authors: Kern E. E. , Anderson D. K. 
Published: April 2003

AbstractDiffusion and anisotropic electrical conductivity measurements have been used to investigate the structure of poly(methacrylic acid) in aqueous solution at various degrees of neutralization. Both kinds of measurement indicate that the polyion chain opens from a coiled to an extended configuration as the chain is neutralized. In addition it was found that, at low concentrations, the opening of the chain is a two‐step process, whereas at higher concentrations the mechanism involves a single step.
Reaction of chlorine‐containing polymers with living polymers
Authors: Minoura Yuji , Hironaka Hisashi , Kasabo Toshiyuki , Ueno Yukio 
Published: April 2003

AbstractA graft polymer was prepared by means of the coupling reaction of chlorinated ethylene–propylene terpolymer with living polystyrene, obtained with a sodium–naphthalene complex as initiator, under various conditions; the grafting efficiency and the percentage of grafting are discussed. Poly(chloroprene), chlorinated butyl rubber, poly(vinyl chloride), poly(epichlorohydrin), and epichlorohydrin–ethylene oxide copolymer were also used as chlorine‐containing polymers. The grafting efficiencies were found to be in the following order: chlorinated butyl rubber > poly(epichlorohydrin) > epichlorohydrin‐ethylene oxide copolymer > chlorinated ethylene‐propylene terpolymer > poly(chloroprene) > poly(vinyl chloride). A graft polymer was obtained from the reaction between chlorinated ethylene–propylene terpolymer and living poly(isoprene), with butyllithium in benzene. The undesirable metal–halogen interchange reaction was considerable.
Effect of acetylene on the γ‐radiation‐induced polymerization of ethylene
Authors: Mitsui Hiroshi , Hosoi Fumio , Hagiwara Miyuki , Kagiya Tsutomu 
Published: April 2003

AbstractThe effects of acetylene on the γ‐radiation‐induced polymerization of ethylene were studied from the viewpoint of the gaseous products and polymer structure. The experiments were carried out under a pressure of 400 kg/cm2; the temperature was 30°C; the does rate was 1.1 × 105 rad/hr; and the acetylene content was 0–20%. The solid polymer was obtained in the polymerization of ethylene containing 2.2% acetylene, while the monomer containing 19.7% acetylene gave a yellowish viscous oil. The polymer yield and molecular weight decreased remarkably with acetylene content. The main gaseous product was hydrogen, and trace amounts of butane, butene‐1, butadiene‐1,3, and benzene and its derivatives were also observed. The rate of formation of hydrogen was almost independent of acetylene content and there was no difference in acetylene contents before and after the irradiation was found. The infrared spectra of the polymers showed the presence of vinylidene, trans‐vinylene, and terminal vinyl unsaturations, 1,4‐disubstituted benzene, and carbonyl groups. The contents of trans‐vinylene, terminal vinyl, and methyl groups increased with acetylene content, and that of vinylidene was independent of acetylene content. The monomer reactivity ratios of ethylene and acetylene were evaluated as 45.5 and 66.0, respectively. On the basis of the results, the effects of acetylene on the γ‐radiation‐induced polymerization of ethylene were discussed.
Photo and thermal polymerization sensitized by donor–acceptor interaction. I.N‐vinyl‐carbazole–acrylonitrile and related systems
Authors: Tazuke Shigeo , Okamura Seizo 
Published: April 2003

AbstractSpontaneous photo and thermal polymerization ofN‐vinylcarbazole (VCZ)–acrylonitrile (AN), VCZ–acetonitrile, AN‐N‐ethylcarbazole, and AN‐ferrocene were studied. These combinations of electron donor with acceptor were thermally rather stable but showed prominent photopolymerizability when the systems were irradiated by near ultraviolet light. The VCZ–AN system showed multireactivity producing VCZ polymer and a copolymer of VCZ with AN. The composition of copolymer was approximately the same as that of polymer produced in radical copolymerization. The effects of additives (DPPH, NH3, H2O, air) indicated simultaneous occurrence of cationic and radical polymerization in the AN–VCZ and acetonitrile–VCZ systems. The results were interpreted on the assumption of initial formation of a cation radical–anion radical pair. The ratio of cationic to radical polymerization differed for photo and thermal polymerization. In no case was anionic polymerization detected.
Polymerization of allyl(vinyl phenyl) ethers and reactions of the resulting polymers
Authors: Kato Masao , Kamogawa Hiroyoshi 
Published: April 2003

AbstractSolution polymerizations of allyl(o‐vinyl phenyl)ether and allyl(p‐vinyl phenyl)ether with cationic and radical initiators were investigated. Soluble polymers were formed in polymerizations with boron trifluoride etherate and with benzoyl peroxide. In polymerization with azobisisobutyronitrile the polymerization in dilute solution gave a soluble polymer, whereas that in concentrated solution gave a crosslinked, insoluble one. For informationon the polymerization behavior some infrared and ultraviolet spectroscopic investigations of the soluble polymers were made. From these results it appears that polymers with pendant allyl groups are formed in polymerization with boron trifluoride etherate at low temperature, and polymers containing pendant vinyl groups and allyl groups are obtained with the two types of radical initiator. Copolymerizations of these monomers with ethyl vinyl ether and styrene with the use of boron trifluoride etherate were sucessfully effected. Such reactions as Claisen rearrangement, crosslinking induced with radical initiators, and epoxidation with perbenzoic acid were examined for the polymers prepared in the polymerization with boron trifluoride etherate. Good results were obtained for the former two reactions. However, the latter was unsuccessful.
Mechanism of three‐dimensional polymerization of the system methyl methacrylate–glycol dimethacrylate. I. Determination of the structure of the three‐dimensional product
Authors: Jokl J. , Kopeček J. , Lím D. 
Published: April 2003

AbstractA method has been developed for determinationof structure of a three‐dimensional methyl methacrylate–glycol dimethacrylate copolymer by using NIR absorption spectrometry. The results show that it is possible to determine the content of pendant vinyl groups in the range of approximately 0.5–18% of the crosslinking agent in the monomer.
On the blue‐colored species, possibly assignable to a radical cation, formed by the aromatic hydrocarbon–sulfur dioxide–oxygen system: The polymerization of olefins initiated by aromatic hydrocarbons–oxygen in liquid sulfur dioxide
Authors: Nagai Toshikazu , Miyazaki Tetsuo , Sonoyama Yuzo , Tokura Niichiro 
Published: April 2003

AbstractIt was found that styrene in liquid sulfur dioxide polymerizes, giving polystyrene readily and quantitatively by addition of such aromatic hydrocarbons as anthracene and trans‐ or cis‐stilbene in the presence of oxygen, and the polymerization proceeds via a cationic process. The observations on the electronic spectra and kinetics in the system suggested that the polymerization was initiated by an electron transfer from the aromatic hydrocarbon to oxygen, followed by the formation of styrene radical cation. Supporting evidence of the radical cation is that 1,1‐diphenylethylene in liquid sulfur dioxide in the presence of oxygen shows a peak at λmax = 605 mμ and reacts to give benzophenone and 1,1,3,3‐tetraphenyl‐butene‐1, which are eliminated by addition of a radical or cation inhibitor.
Polymerization of methyl methacrylate in a tetrahydrofuran–maleic anhydride system. Part II
Authors: Berger Jozef , Lazár Milan 
Published: April 2003

AbstractA donor–acceptor complex consisting of tetrahydrofuran and maleic anhydride initiates photochemical and thermal polymerization of methyl methacrylate. The mechanism of the transformation of this complex was investigated by studying changes in its electrical conductivity, its chemiluminescence, and various influences on its initiating capability (water, air, DPPH, substitution of styrene for methyl methacrylate and of 1,4‐dioxane for tetrahydrofuran). It has been shown that initiation by radicals cannot be clearly excluded and that ionic radicals form in the system and can initiate the anionic growth of the chain.
Studies of the graft copolymerization of methyl methacrylate by means of the photochemical reduction of ceric ion adsorbed on cellulosic materials
Authors: Ogiwara Yoshitaka , Kubota Hitoshi , Ogiwara Yukie 
Published: April 2003

AbstractIt was observed that the rate of reduction of ceric ion adsorbed on cellulose was remarkably accelerated by irradiation with ultraviolet light, and this behavior depended upon the kind of cellulose. When the graft copolymerization of methyl methacrylate on cellulose with adsorbed ceric ion was carried out by irradiation with ultraviolet light, the percent grafting decreased for softwood, bleached sulfite pulp and increased for hardwood semichemical pulp. The average molecular weight of the grafts was observed generally to decrease. If it is assumed that the ceric ions, which are reduced at an accelerated rate in the early stages of reaction with SCP, do not participate in the graft formation, a relation is observed between the modified amount of reduced ceric ion and the number of grafted chains formed, and the molar ratios of these quantities are 12:1 without irradiation and 75:1 to 100:1 with irradiation. Even when the rate of reduction of ceric ion is accelerated, the increase in the number of grafted chains is found to be very small.
Kinetics of the gamma‐radiation‐induced polymerization of ethylene in tert‐butyl alcohol
Authors: Suganuma Fujio , Mitsui Hiroshi , Machi Sueo , Hagiwara Miyki , Kagiya Tsutomu 
Published: April 2003

AbstractThe gamma‐radiation‐induced polymerization of ethylene in the presence of 13–30 ml of tert‐butyl alcohol was carried out under a pressure of 120–400 kg/cm2 at a dose rate of 1 × 103 to 2.5 × 104 rad/hr at 30°C with a 100 ml reactor. The polymerization rate and the molecular weight of the polymer increased with reaction time and pressure and decreased with amount of tert‐butyl alcohol. The polymer yield increased almost proportionally with the dose rate, while the molecular weight was almost independent of it. These results were graphically evaluated, and the rate constants of initiation, propagation, and termination for various conditions were determined. No transfer was observed. On the basis of these results the role of tert‐butyl alcohol in the polymerization is discussed.
Vinyl monomer polymerization mechanism in the presence of trialkylboranes
Authors: Grotewold J. , Lissi E. A. , Villa A. E. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate in the presence and in the absence of triethylborane and different inhibitors was carried out. An ethyl radical displacement reaction between the inhibitor radical (produced through the reaction between a radical chain and the inhibitor) and the triethylborane is postulated. This new chain‐transfer reaction explains the large excess of inhibitor which must be added in the presence of triethylborane in order to suppress the production of high molecular weight polymer. The results are in agreement with a typical free‐radical mechanism.