bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneous catalysis by polyelectrolyte. I. Polyelectrolyte influence on the solvolysis and deamination
Authors: Nishiyama Yoshihiro , Moroe Ichiro , Kitano Hiromi , Okubo Tsuneo , Ise Norio 
Published: April 2003

AbstractHeterogeneous or homogeneous polyelectrolyte influences on the solvolyses of t‐butyl chloride and α‐phenethyl chloride were studied. Anionic polymers enhanced the reaction rate by stabilizing the intermediate point dipole (ionic strength effect); cationic polymers with chloride ions as gegenions retarded the reaction by the mass action law (common ion salt effect), thus supporting the theory of Ingold et al. On the other hand, neutral polymer resins retarded the reaction probably because of the binding of the substrate on the resin surface. By the addition of a neutral polymer resin. Amberlite XAD‐4 the net steric course of the solvolysis of α‐phenethyl chloride was slightly changed from inversion to racernization, whereas anionic resins (Amberlite IR‐124) showed no effect. The heterogeneous polymer resin effect on the dearnination of α‐phenethyl amine was also studied. An anionic resin (IR‐124) retarded the reaction slightly and a neutrai resin (XAD‐4) retarded it to a great extent. A cationic resin (Dowex 1 × 8) accelerated the reaction, although slightly. The net steric course of the deamination was changed from inversion to racemization in the order XAD‐4 > Dowex 1 × 8 > IR 124. The heterogeneous polymer effect of the stereochemistry depended mainly on the hydrophobicity: i.e., the ability to bind the substrate on the surface of resin.
Relationships of graft polymerization of vinyl monomers onto cellulose. Reaction kinetics and polymer structure
Authors: Kurliankina V. I. , Molotkov V. A. , Klenin S. I. , Liubina S. Ya. 
Published: April 2003

AbstractGraft polymerization of acrylamide and sulfuric salt of 2‐methyl‐5 vinylpyridine onto cellulose using CO(III) salts was studied. It was shown that graft polymerisation of water‐soluble polymers can be described by general relationships of radical reaction. The relation between elementary reaction constants of the formation and termination of active centers in cellulose, as well as relation between constants of the propagation, transfer and termination of chains were determined for different cellulose materials and monomers. The translational diffusion, sedimentation, viscosity, and flow birefringence of copolymers have been investigated in different solvents. Experimental data showed that the copolymers obtained are graft copolymers with two to five grafted chains onto macromolecules. The minimum distance between the branch points is 100 ± 20 glucoside units. The peculiarity of these copolymers is relatively low polydispersity. The conformation of macromolecules of such copolymers in solution depends on the compatibility of the copolymer components and the thermodynamic properties of the solvent.
Synthesis and polymerization of γ‐alkoxy‐β‐hydroxypropyl acrylates
Authors: Lu Chengxun , Chen Naichun , Gu Zhong Wei , Feng Xinde 
Published: April 2003

AbstractSeveral γ‐alkoxy‐β‐hydroxypropyl acrylates were synthesized and polymerized. Both poly(MHPA) (IVd) and poly(MHPMA) (IVa) hydrogels possess high values of equilibrium water content, about seven and three times, respectively, that of the poly(β‐hydroxyethyl methacrylate) hydrogel. These rather high values are attributed tentatively to the presence of a hydrophilic γ‐methoxy‐β‐hydroxypropyl side group on the acrylic backbone.
Polymerization of oriented monomers. V. Radiation‐induced polymerization of 3n‐dodecyl‐1‐vinylimidazolium iodide in micellar aggregates
Authors: Paleos C. M. , Voliotis S. , Margomenou‐Leonidopoulou G. , Dais Photis 
Published: April 2003

AbstractIn the present study radiation‐induced polymerization of 3n‐dodecyl‐1‐vinylimidazolium iodide (I) in micellar aggregates was investigated. For comparison, the corresponding isotropic polymerization of I was also studied. Micellization was obtained in concentrated aqueous solutions; that is, above the monomer's critical micelle concentration (CMC) polymers obtained by both modes of polymerization were treated similarly and subsequently subjected to physical characterization. The main purpose of this study was to investigate whether the degree of organization of the monomer in micelles would affect polymer properties. Attempts to determine tacticity by 13C‐NMR spectrometry failed because of the particular structure of the polymer. Crystallization of these polymers from ethyl alcohol or acetone was not possible as indicated by x‐ray powder diffraction patterns that were characteristic of amorphous polymers. On the other hand, viscosity data of polymers do not depend on the mode of polymerization. It is therefore concluded that micellar aggregates are not sufficiently organized to affect polymer properties.
Starshaped block copolymers. I. Synthesis of new A(B)2 starshaped block copolymers based on vinyl or diene hydrocarbons (A) and oxirane (B)
Authors: Huynh‐Ba‐Gia  , Jérôme R. , Teyssié Ph. 
Published: April 2003

AbstractNaphthalene‐terminated polyvinyl aromatics and polyisoprene were obtained successfully. These functional polymers were metalated by potassium in THF at 25°C. The formation of a stable dinegative ion is observed unless the naphthalene is directly attached to the end of the polyvinyl aromatics, in which case a few isoprene units can be advantageously inserted between the naphthalene end group and the polyvinyl aromatics. The polymeric and stable dinegative ion polymerizes oxirane by both anionic sites and forms three‐branched starshaped block copolymers.
Asymmetric porous emulsion film
Authors: Okubo Masayoshi , Takeya Tetsuro , Tsutsumi Yoshitaka , Kadooka Tsuneo , Matsumoto Tsunetaka 
Published: April 2003

AbstractThe formation mechanism of an “asymmetric” porous structure for the film cast from ethyl acrylate‐methyl methacrylate copolymer emulsion prepared by emulsifire‐free emulsion polymerization was investigated. The formation of this structure was affected by the emulsion stability which was varied by the postaddition of sodium sulfate or sodium dodecyl benzene sulfonate. It is concluded that it is derived from the production of porous skin film at the emulsion‐air interface and the precipitation of flocculated particles at the bottom of emulsion during drying process.
Cyclopentadienylation of PVC: Characterization and thermal and thermooxidative degradation studies
Authors: Iván Béla , Kennedy Joseph P. , Kelen Tibor , Tüdös Ferenc 
Published: April 2003

AbstractPVC has been cyclopentadienylated by two conventional basic, LiCp and NaCp, and a new acidic, Me2CpAl, cyclopentadienylating agent. PVCs treated with basic cyclopentadienylating agents undergo severe random dehydrochlorination and exhibit a significant decrease in thermal and thermooxidative stability. In contrast, according to ozonization and degradation experiments, Me2CpAl does not cause dehydrochlorination during cyclopentadienylation. The thermal stability of PVC treated with relatively high concentrations of Me2CpAl and Me3Al at 25°C markedly increases due to substitution of labile chlorines in PVC with methyl groups. Initial thermal dehydrochlorination behavior of virgin PVC and samples treated with Me2CpAl at −30°C are similar. In contrast, thermooxidative stability decreases on Me2CpAl treatment at −30°C; this is attributed to ease of oxidation of pendant cyclopentadienyl groups; that is, the formation of peroxy radicals that may initiate dehydrochlorination by attacking unchanged repeat units in PVC. Acceleration of thermal dehydrochlorination disappears and the length of polyene sequences is reduced on Me2CpAl and Me3Al treatment. These observations are attributed to differences in rates of protonation‐deprotonation; that is, rates of reinitation of zipping of treated and untreated PVCs during thermal degration. The effect of traces of aluminum residues on degradation of modified PVCs, however, cannot be neglected.
The influence of steric factors on the mechanism of copolymerization of phenylvinyl alkyl ethers and maleic anhydride
Authors: Fleš D. , Vuković R. , Kurešević V. , Radičevic R. 
Published: April 2003

AbstractBy assuming that the initial rate of copolymerization (Rp) of phenylvinyl alkyl ether (I) and maleic anhydride (MAn) equals the sum of the rate of polymerization of free monomers Rp(f) and CT complex monomers Rp(CT) the reactivity ratios k1c/k12 and k2c/k21 were calculated for copolymerization of I(R = Me, n‐Pr, iso‐Pr, and sec‐Bu) and MAn from the change of copolymerization rate with monomer feed at a constant total monomer concentration. From the equation Rp = Rp(f) + Rp(CT) were calculated Rp(f) and Rp(CT) by applying the generalized model described by Shirota and coworkers and it was found that the participation of CT complex monomers increases with an increase in total monomer concentration in the feed. It was also found that the degree of CT complex monomer participation depends largely on the steric factors. In the copolymerization of I which contains bulky isopropyl or sec‐butyl group even in the dilute solutions, copolymerization proceeds by the addition of CT complex monomers.
Propagation/depropagation equilibrium and structural factors in the radiation degradation of poly(olefin sulfone)s
Authors: Bowmer Trevor N. , O'Donnell James H. 
Published: April 2003

AbstractThe principal volatile products observed after γ irradiation of nine different poly(olefin sulfone)s in the solid state were the two comonomers, i.e., the respective olefin and sulfur dioxide. An exponential increase in yield, G(volatile products), with increasing irradiation temperature, Tirr, was observed for each copolymer through the ceiling temperature, Tc, for the corresponding propagation/depropagation equilibrium. Thus the G value increased by ca. 3 orders of magnitude from Tirr = 0.7 Tc to Tirr = 1.3 Tc for all of the poly(olefin sulfone)s. Depropagation sensitivity was considered to be best measured by G(SO2) since radiation induced, cationic homopolymerization of the product olefin occurred to a variable extent. Five of the poly(olefin sulfone)s had similar rates of depropagation at their respective Tc's but the polysulfones of 1‐hexene, cyclohexene and 2‐butene showed anomalously high depropagation rates. This may be related to greater steric hinderance to segmental chain mobility in the polysulfones of the 1,2 disubstituted olefins. Poly(1‐hexene sulfone) appears to be anomalous, as in other respects.
Copolymerization of studies. Copolymerization of methyl α‐cyanocrotonate with styrene, acrylonitrile, and vinyl acetate
Authors: Raiter Julia , Kohn David H. 
Published: April 2003

AbstractCopolymers of methyl α‐cyanocrotonate with styrene, acrylonitrile, and vinyl acetate were prepared in bulk by free radical initiation. The copolymerization parameters were determined for each pair by several methods. The basic properties, that is, intrinsic viscosity, solubility, melting range, and glass transition temperature of the obtained copolymers, were determined.
Polymerization of aromatic nuclei. XXV. ESR and chemical studies on the radical cation nature of poly(p‐phenylene)
Authors: Jones Martin B. , Kovacic Peter , Howe Russell F. 
Published: April 2003

AbstractThe radical cation nature of poly(p‐phenylene) (PPP) was examined by electron spin resonance (ESR) and chemical means. ESR studies revealed a radical concentration of 1.0 × 1021 spins/g for the crude polymer. Workup with aqueous acid decreased the value to 1.5 × 1018 spins/g. Reactions of the polymer with certain nucleophiles followed the half‐regeneration mechanism, whereas with others, electron transfer mainly occurred. The origin of halogen in the polymer was found to arise from reaction of the radical cation with the oxidant, and not with halide during workup. Oxidation of PPP with various species increased the concentration of radical cations.
N‐vinyl carbazole copolymers
Authors: Mulvaney J. E. , Gromelski S. , Rupp R. 
Published: April 2003

AbstractThe synthesis of N‐vinyl carbazole (VCbz) copolymers, some of which contain electron‐accepting groups, is described. The new copolymers are: copoly[N‐vinyl carbazole‐di(2‐N‐carbazylethyl)‐fumarate](II); copoly(N‐vinyl carbazole‐vinyl‐2,4‐dinitrobenzene‐sulfonate)(IV); copoly(N‐vinyl carbazole‐vinyl‐2,4‐dinitrobenzene‐sulfenate)(V); copoly(n‐butyl acrylate‐t‐butyl peracrylate)(VII); copoly(n‐butyl acrylate‐t‐butyl acrylate‐graft‐N‐vinyl carbazole)(VIII).
Synthesis of asymmetric cyclopropyl acids and amines
Authors: Overberger C. G. , Nishiyama T. 
Published: April 2003

Abstract(+) (S)‐ and (−) (R)‐trans‐1,2‐cyclopropanedicarboxylic acids (C3A), (+) (S)‐ and (−) (R)‐trans‐1,2‐diaminocyclopropanes (C3B), (+) (S)‐ and (−) (R)‐trans‐2‐phenylcyclopropylamines (øC3B), (+) (S)‐ and (−) (R)‐trans‐1,2‐bis(methylamino)‐cyclopropanes (C3MB), and (+) (S)‐ and (−) (R)‐trans‐(2‐phenylcyclopropyl)‐methylamines (øC3MB) were prepared.
Copolymerization parameters of methyl methacrylate and acrylic acid
Authors: Stahl G. Allan 
Published: April 2003

AbstractThe relative reactivity of acrylic acid is known to be influenced by the polymerization medium. Nonetheless, the more commonly used reactivity ratios do not show this dependence because they were calculated from low‐conversion polymerizations. We have studied the copolymerization of acrylic acid and methyl methacrylate in a number of non‐hydrogen‐bonding and hydrogen‐bonding solvents. We found that the acrylic acid fraction in the copolymer was larger when copolymerized in a non‐hydrogen‐bonding medium and that the methyl methacrylate fraction was larger when copolymerized in a hydrogen‐bonding medium. The precise reactivity ratios were reported when toluene, benzene, isopentyl, acetate, ethyl acetate, methyl formate, and tert‐butyl alcohol were used as the polymerization medium. The values were obtained by chromatographic analysis of residual monomer, followed by computation based on the nonlinear, least‐squares technique of Tidwell and Mortimer.
Kinetics and mechanism of urethane formation catalyzed by organotin compounds. I. The reaction of phenyl isocyanate with methanol in dibutyl ether under the action of dibutyltin diacetate
Authors: Van Der Weij F. W. 
Published: April 2003

AbstractThe kinetics of the dibutyltin diacetate (DBTDA) catalyzed reaction of phenyl isocyanate with methanol in dibutyl ether at 25°C were studied by monitoring the rate of change in the absorbance of the reaction mixture at 281.6 nm. The rate equation was

The value of k was calculated at 0.96 liter/(mole sec). In addition, it was ascertained that protons behave like extremely strong inhibitors for the catalyzed reaction. On the basis of these data a mechanism for urethane formation is proposed. The subsequent reaction steps are (1) complexation of methanol to DBTDA, (2) dissociation of the complex into a proton and an anion of composition {(n‐C4H9)2Sn(OCOCH3)2(OCH3)}‐, (3) insertion of the isocyanate into the tin‐alkoxy bond (the rate‐determining step), and (4) methanolysis of the urethane precursor formed with simultaneous regeneration of the anion. With this mechanism it is possible to explain the observed kinetics as well as the deviations that occur in the rate expression if strong acids are added to the reaction mixture. The latter effect is caused by a shift in the equilibrium that describes the dissociation of the complex into ions. The retardation of the reaction by weak acids like acetic acid is caused by complexation of DBTDA by the acid.
The synthesis of biscitraconimides and polybiscitraconimides
Authors: Galanti Anthony V. , Scola Daniel A. 
Published: April 2003

AbstractA series of N‐alkylene biscitraconimides was synthesized from the corresponding N‐alkylene‐biscitraconamic acids or directly from itaconic anhydride and a homologous series of aliphatic diamines, H2N(CH2)nNH2, where n = 2 through 12. The biscitraconamic acids were synthesized from the α,ω‐diamino‐alkanes and itaconic anhydride. Isomerization of itaconic anhydride to citraconic anhydride occurs in the presence of the diamines to yield biscitraconamic acids instead of bisitaconamic acids expected and observed in similar studies. The intermediate biscitraconamic acids or the biscitraconimides were polymerized thermally between 175 and 225°C to tough ambered‐colored films of polybiscitraconimides that exhibit good thermal stability.
Redox cationic polymerization: The diaryliodonium salt/ascorbate redox couple
Authors: Crivello J. V. , Lam J. H. W. 
Published: April 2003

AbstractStrong Brønsted acids are produced on reduction of diaryliodonium salts containing anions of the type BF4−, AsF6−, PF6−, SbF6− by ascorbic acid and its derivatives in the presence of catalytic amounts of copper salts. The cationic polymerizations of cyclohexene oxide, tetrahydrofuran, and s‐trioxane were studied using the diaryliodonium salt/ascorbate redox couple.
Stepwise thermal degradation of a polybenzimidazole foam
Authors: Chatfield Dale A. , Einhorn Irving N. 
Published: April 2003

AbstractThe stepwise thermal degradation of a polybenzimidazole (PBI) foam, prepared from 3,3′‐diaminobenzidine and isophthaldiamide, has been studied under conditions of pyrolysis and nonflaming oxidative degradation in a thermal analyzer using gas and liquid chromatographic separation and mass spectrometric and infrared detection techniques. The recoveries of sample weight, as degradation products, were quantitative over the entire temperature ranges studied (100–300, 300–570, 570–700, and 700–1000°C for pyrolysis; and 100–570 and 570–900°C for nonflaming oxidation). In pyrolysis, 17 volatile compounds were identified with NH3 and CH4 accounting for 94 and 57 mole % of the total mass loss between 300–570 and 570–700°C, respectively. Above 700°C, HCN and H2 were formed from degradation of arylnitrile‐containing oligomers. The thermal and oxidative degradation of three substituted benzimidazole monomers was also studied, and the relative ratios of N2, NH3, and HCN that were produced from each, when compared with PBI, support a mechanism for degradation that favors cleavages that least alter the conjugation of the polymer backbone. In the presence of air, PBI formed stable oxygen‐containing residues that decomposed at high temperatures to N2, CO2, and H2O almost exclusively. Large quantities of H2 and N2 from model compounds support results from PBI that suggest that degradation begins with total erosion of the imide ring at 570°C and the formation of more condensed heterocyclic species. These quantitative techniques are generally applicable to the study of all polymeric materials.
Chemistry of dicumyl peroxide‐induced crosslinking of linear polyethylene
Authors: Hulse George E. , Kersting R. James , Warfel David R. 
Published: April 2003

AbstractThe course of intermolecular reactions induced by peroxide decomposition in linear polyethylene has been determined and compared with similar reaction systems in which the substrate is a lowmolecular‐weight alkane. Efficiency of intermolecular coupling is 40% for an alkane and 25–30% for the polymer system. Competing reactions, which reduce coupling efficiency, are mainly disproportionation of the initially formed radicals and to a minor extent further reactions involving the products from the peroxide decomposition. The low efficiencies found are similar to those well studied when initial radicals are produced by radiolysis in polymer and alkane systems.
Controlled introduction of allylic chlorines into poly(vinyl chloride)
Authors: Iván Béla , Kennedy Joseph P. , Kelen Tibor , Tüdos Ferenc 
Published: April 2003

AbstractColorless poly(vinyl chloride)s (PVC) containing up to 1.6 allylic chlorines per molecule have been prepared by controlled random dehydrochlorination with a strong base. The effect of temperature in the −50 to +24°C range on the number of allylic chlorines and color of PVC has been investigated by ozonization experiments and UV–visible spectroscopy. A two‐parameter kinetic model has been developed which quantitatively accounts for the observations and points the way for further research.
Synthesis and properties of novel poly(N‐oxyimide)s
Authors: Ibrahim A. Mahammad , Mahadevan V. , Srinivasan M. 
Published: April 2003

AbstractNovel poly(N‐oxyimide)s (PNOI) were synthesized by the room temperature polycondensation of N,N′‐dihydroxypyromellitimide (I) with dichloro compounds in N,N‐dimethylformamide (DMF) in the presence of triethylamine both as base as well as catalyst. The dichloro compounds used were 1,4‐bis(chloromethyl)‐2,5‐dimethylbenzene (II), 1,5‐bis(chloromethyl)‐2,4‐dimethylbenzene (III), 1,4‐bis(chloromethyl)‐2,5‐dimethoxybenzene (IV) and 1,4‐dichlorobut‐2‐yne (V). Polymer synthesis, characterization, and properties such as density, viscosity, solubility, crystallinity, and thermal stability were described. Two model compounds, viz. (i) MNOI‐1 from N‐hydroxyphthalimide and a dichloro compound (III), (ii) MNOI‐2 from I and benzyl chloride were also synthesized to confirm the formation of polymers. The polymers thus obtained had high intrinsic viscosities in the range 1.09–1.18 dl/g. The thermal decomposition of the polymers started around 260°C with 20–25% decomposition and about 50% weight loss was observed at 400°C.
Synthesis and characterization of polyesters derived from polychlorinated aromatic diacids
Authors: D´iaz Fernando R. , Larraín Rafael R. , Fresno Andrés , Ramirez René S. 
Published: April 2003

AbstractNew, thermally stable polyesters with varying chlorine content were prepared by solution and interfacial polycondensation between chlorinated aromatic dichlorides (perchloroterephthaloyl dichloride, 2,5‐dichloroterephthaloyl dichloride, and perchloro‐4,4′‐dichloroformyl biphenyl with different aliphatic and aromatic diols). The polymers were characterized by infrared spectroscopy, elemental analysis, differential scanning calorimetry, and thermogravimetric analysis. Their solubilities and molecular weights were also determined. The influence of chlorine content on the thermal properties of the polymers is discussed.
Silylation of water glass. II. Synthesis and copolymerization of carbon‐functional silylated silicic acid
Authors: Inoue Hiroshi , Kohama Shigemi 
Published: April 2003

AbstractCarbon‐functional silylates were prepared by reacting trialkoxysilanes and trimethylchlorosilane with silicic acid which had been derived from aqueous sodium silicate solution. The trialkoxysilanes used here were polymerizable silanes, i.e., vinyltriethoxysilane, (γ‐methacryloyloxypropyl)trimethoxysilane, and (p‐vinylphenyl)triethoxysilane. Molecular weights of these silylates containing more than one mole of the functional group ranged from 4000 to 9000. These silylates were found to serve as effective crosslinking agents for vinyl polymerization. However, soluble copolymers could be obtained under appropriate conditions, such as high dilution and low conversion in copolymerization. Glass transition temperatures (Tg) of the soluble copolymers were measured by differential scanning calorimetry to determine the effect of the silylates on the thermal properties of the copolymers. A slight variation of the Tg of these copolymers was observed when small amounts of the silylates were incorporated. It was also noticed that the water repellency of these copolymers was influenced by their composition.