bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic grafting from carbon black. II. Polymerization of styrene initiated by CO+ClO group on the surface of carbon black
Authors: Tsubokawa Norio 
Published: April 2003

AbstractThe cationic grafting of polystyrene initiated by carbon black containing the CO+ClO group was investigated. The introduction of CO+ClO groups onto a carbon black surface was achieved by the reaction of AgClO4 with carbon black that contained a COCI group. The latter was introduced by the reaction of carboxyl groups with SOCl2. It was found that polystyrene chains could be grown from CO+ClO groups on the surface of carbon black. Moreover, polystyrene was effectively grafted from carbon black: the grafting ratio at 20°C increased to 58% as conversion increased. Furthermore, the grafting ratio and molecular weight of ungrafted polystyrene decreased with an increase in polymerization temperature. These results were explained by the fact that the increasing temperature of the polymerization caused an increase in the rate of chain transfer reaction of the growing polymer chain to the monomer. The carbon black obtained from the reaction produced a stable colloidal dispersion in a good solvent for polystyrene.
Graft polymers with macromonomers. II. Copolymerization kinetics of methacrylate‐terminated polystyrene and predicted graft copolymer structures
Authors: Schulz G. O. , Milkovich R. 
Published: April 2003

AbstractCopolymerization studies of methacrylate‐terminated polystyrene macromonomers (M1) with several comonomers (M2) verified the modified kinetic scheme and permitted prediction of graft polymer compositions and structures. Instantaneous and cumulative copolymer compositions, average graft distributions, and grafts per molecule are predicted from FORTRAN IV or BASIC programs. The r2 relative reactivity ratios determined from styrene copolymerization (0.61) or from low conversion acrylic monomer in aqueous suspension (∼0.4) had good agreement with literature values (about 0.6 and 0.4, respectively). Decreased macromonomer reactivity determined at high acrylic monomer conversions was attributed to phase separation phenomena. The Macromers also exhibited lower reactivity than predicted when copolymerized with acrylic monomers in DMSO/benzene solutions (r2 ∼ 0.8).
Asymmetric selective polymerization of racemic 1,2‐diphenylethyl methacrylate with the ethylmagnesium bromide‐(−)‐sparteine complex
Authors: Okamoto Yoshio , Yashima Eiji , Hatada Koichi , Yuki Heimei , Kageyama Hiroyuki , Miki Kunio , Kasai Nobutami 
Published: April 2003

AbstractAsymmetric selective (or stereoelective) polymerization of racemic 1,2‐diphenylethyl methacrylate (DPEMA) with ethylmagnesium bromide (EtMgBr)‐(−)‐sparteine catalyst was studied in toluene at −78°C. In the polymerization (S) enantiomer was consumed preferentially and the enantiomeric excess of initially polymerized (S) enantiomer was consumed preferentially and the enantiomeric excess of initially polymerized DPEMA was greater than 90%. Optically pure (R) monomer was recovered at about 70% polymer yield. Poly(DPEMA) obtained with EtMgBr‐(−)‐sparteine complex was highly isotactic. It was found in the polymerization of optically active DPEMA that optical rotation of poly(DPEMA) was dependent on the tacticity and that isotactic and syndiotactic poly(DPEMA)s showed opposite optical rotations. Circular dichroism spectra of the optically active polymers were measured.
Polymerization of acrylonitrile initiated by ceric ion–citric acid redox system
Authors: Misra G. S. , Bassi P. S. , Abrol S. L. 
Published: April 2003

AbstractHeterogeneous polymerization of acrylonitrile initiated by ceric ammonium sulfate–citric acid (C.A.) redox system is reported at 35 ± 0.2°C under nitrogen atmosphere. The rate of monomer disappearance is found to be proportional to [C.A.]0, [Ce4+]0.63, and [Monomer]1.59. The rate of ceric ion disappearance is directly proportional to ceric ion concentration but independent of monomer concentration. The initial rate was independent of [H2SO4]. The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreasing ceric ion concentration. Activation energy was found to be 27.9 kJ/mol.
Low‐temperature thermal decomposition of an epoxy resin
Authors: Grayson Michael A. , Wolf Clarence J. 
Published: April 2003

AbstractThe thermal decomposition of the epoxy resin system, MY720 (70 wt % tetraglycidyl diaminodiphenyl methane), cured with Eporal (diamino diphenyl sulfone), was investigated at 125–215°C. The primary decomposition product was propenal. Several other aldehydes were observed; however, they are formed during cure and are not thermal decomposition products. The apparent activation energy for the production of propenal was 67 kJ/mol (16 kcal/mol). Possible mechanisms for the source of this compound are discussed.
Hydrogen as a chain terminator in continuous gas phase polymerization of propylene
Authors: Ross James F. 
Published: April 2003

AbstractThe effects of hydrogen on both degree and rate of polymerization have been determined for continuous, gas phase polymerization of propylene at industrial reactor conditions. The effects of molecular weight using three modifications of TiCl3–DEAC catalyst are correlated by Natta's equation, using number average molecular weights determined from polymer melt flow rate. The coefficients of Natta's equation, when correlated against temperature in Arhenius plots, imply that the most active catalyst is diffusion controlled because the activation energy is abnormally low. Hydrogen increases overall polymerization rate. Rate is correlated by modification to Natta's equation that accounts for hypothesized increase in active sites on catalyst surface due to adsorbed molecular hydrogen.
Studies on vinyl photopolymerization using a macromolecular C.T. Complex between poly(N‐vinyl carbazole) and bromine as the photoinitiator
Authors: Ghosh Premamoy , Ghosh Tapas Kumar 
Published: April 2003

AbstractPhotopolymerization of methyl methacrylate (MMA) was studied at 40°C using a macromolecular C.T. Complex between poly(N‐vinyl carbazole) and bromine, expressed in brief as (PNVC–Br2) complex, as the photoinitiator. Initiator exponent was 0.40 for [PNVC–Br2] ≤ 2.5 × 10−3 mol L−1 and practically zero for [PNVC–Br2] > 2.5 × 10−3 mol L−1. Monomer exponent in different diluent systems such as benzene, carbon tetrachloride, and acetone was close to 1.0. Low initiator exponent (<0.5) is explained on the basis of an initiator‐dependent termination mechanism, in addition to the usual bimolecular termination. Analysis of kinetic data indicates that the initiator‐dependent termination is primarily due to degradative initiator transfer and that due to primary radicals is considered inconsequential in view of monomer exponent being close to unity. The non‐ideal termination process assumes over‐whelming prominence at high [PNVC–Br2].
Synthesis and polymerization of optically active L‐[α‐(N‐p‐acryloxybenzoyl)alanine ethyl esters]
Authors: Lu Chengxun , Overberger C. G. 
Published: April 2003

AbstractNew optically active monomers L‐[α‐(N‐p‐acryloxybenzoyl)alanine ethyl esters] (I) and their polymers were synthesized. The title monomers (I) were prepared by the reaction of 1‐p‐acryloxybenzoyloxy‐4‐chlorobenzotriazoles (II) with L‐alanine ethyl ester hydrochloride, by aminolysis of the active monoester. The new typical active ester (II) was synthesized by the N‐hydroxy compound active‐ester methods in excellent yield. Before the synthesis of the optically active monomers was carried out, a model study of the aminolysis of the two active esters was performed.
Electron spin resonance studies of spin labeled alternating functional copolymers
Authors: Andreis M. , Veksli Z. , Vuković R. , Fleš D. 
Published: April 2003

AbstractThe spin‐labeled and spin‐probed alternating copolymers of poly(phenylvinyl alkyl ethers) with various alkyl groups (Me, Et, sec‐Bu) in the ether moiety were investigated by electron spin resonance (ESR). Measurements were taken in different solvents over a wide range of concentration. Studies reveal that the molecular motion of spin‐labels and spin‐probes depends on the bulkiness of the alkyl group at the solvent concentration in which the effect of segmental rotation is dominant. The implication of the type of chemical bonding on the nitroxide motion is discussed.
Reactions in the presence of organic phosphites, I: High temperature amidation in the absence of solvents
Authors: Aharoni Shaul M. , Hammond Willis B. , Szobota John S. , Masilamani Divakar 
Published: April 2003

AbstractWhen reacted for periods of 5–10 min at temperatures of about 280–300°C in the presence of certain organic phosphites polymers that contain available carboxy and aliphatic amine groups undergo amidation. This reaction can increase the molecular weight of many aliphatic polyamides by their self‐reaction in an extruder. Block or graft copolymers can be formed by reacting polymers that contain aliphatic amines with others that contain carboxyl. Studies of model compounds in the companion article (II) indicate that polymerization proceeds through an diaryloxy or dialkoxy amino phosphine intermediate to produce amide bonds and disubstituted phosphite reaction by‐products. In the absence of primary amines in the reaction mixture an ester is slowly formed from the carboxyl end group of the polymer and the oxysubstituent of the phosphite. In no case was a phosphorus‐containing mixed anhydride detected. The mechanistic identity of the low temperature reactions in article II and the high temperature reactions in this article has not been proved conclusively, however.
Ablative photodecomposition of polymer films by pulsed far‐ultraviolet (193 nm) laser radiation: Dependence of etch depth on experimental conditions
Authors: Srinivasan R. , Braren Bodil 
Published: April 2003

AbstractData on the ablative photodecomposition of three condensation polymers [polyimide, poly(ethylene terephthalate), and polycarbonate] and one addition polymer (polymethyl methacrylate) by laser pulses at 193 nm are presented. The etch depth/pulse is a linear function of the number of pulses at constant laser fluence. It varies with the logarithm of the fluence in a linear manner at different fluences. The etch depth is independent of the atmosphere above the film, whether it is air at 1 atm, or a vacuum. The etching of PMMA at fluences > 100 mJ/cm2 is believed to follow a mechanism different from the process at lower fluences. Etching of polyimide and polyethylene terephthalate at 248 and 308 nm is also reported. The mechanism of etching by laser radiation may receive greater contribution from a thermal process with increasing wavelength. This is manifested in the etch depth versus log fluence plot by sharp changes in slope.
Catalyseurs Ziegler‐Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. III. Systèmes catalytiques à hautes performances comprenant un solide ternaire: MgCl2, ester aromatique, TiCl4
Authors: Spitz R. , Lacombe J. L. , Guyot A. 
Published: April 2003

AbstractAn examination of the precatalyst which contains three compounds (MgCl2–TiCl4‐aromatic ester) uncovered numberous properties that apparently are common to all precatalysts and have already been observed in the simpler systems: a continous decrease in the polymerization rate during polymerization, characterized by a deactivation index that does not depend on the precatalyst but only on the cocatalyst; isotacTiClty control by the [AI]/[aromatic ester] ratio in the cocatalytic solution; and fast and reversible control of kinetics and tacTiClty by the same ratio. The precatalyst prepared by impregnation of the aromatic ester in MgCl2 or MgCl2–TiCl4 presents moderate or no improvement when compared with the simpler MgCl2–TiCl4 catalysts. The yellow precatalyst prepared by milling MgCl2 with the aromatic ester and impregnating with TiCl4 are the only products that provide high activity and isotactic index above 95% simultaneously, as revealed by the patent literature. Interpretation of the role played by the electron donor, based on infrared studies, are proposed: in the precatalyst it controls fixation of TiCl4 on MgCl2; in the cocatalytic solution it regulates the isospecificity of the active site by contact with the alkylaluminium‐aromatic ester complex and slows polymerization. Free electron donor gradually poisons the active centers.
Applicability of the Mayo–Lewis equation to high conversion copolymerization of styrene and methylmethacrylate
Authors: O'Driscoll K. F. , Kale L. T. , Rubio L. H. Garcia , Reilly P. M. 
Published: April 2003

AbstractIn contradiction to reports from this and other laboratories, this study reports that the integrated Mayo–Lewis equation, or Meyer–Lowery equation, adequately describes the high‐conversion free radical copolymerization of styrene and methylmethacrylate. The copolymerization was monitored by following the changes in the feed composition using NMR, as well as determination of the resulting copolymer compositions by NMR and UV. “Error in all Variables” statistical techniques were used to produce estimates of the reactivity ratios. The reactivity ratios estimated were, from feed composition, NMR, r1 (styrene) = 0.472, r2 = 0.454, from copolymer composition, UV, r1 = 0.497, r2 = 0.464, and NMR, r1 = 0.432, r2 = 0.422.
PVC miniemulsion polymerization II. Particle and droplet growth as a function of conversion
Authors: Dewald R. C. , Hart L. H. , Carroll W. F. 
Published: April 2003

AbstractGrowth of two droplet families and a polymer seed family as a function of percent monomer conversion in PVC miniemulsion synthesis demonstrates that polymerization in droplets predominates to ∼ 30–40% conversion, whereupon polymerization of seed becomes favored. This difference appears to be due to a liquid‐to‐solid phase change in the forming particles during the course of polymerization.
Copolymerization reactivity of poly(methyl methacrylate) macromer
Authors: Fukutomi Takashi , Yokota Atsushi , Ishizu Koji 
Published: April 2003

AbstractPoly(methyl mehtacrylate)(PMMA) macromers with several vinyl groups at both chain ends were synthesized by the mechanical scission reaction of the main chain in the presence of p‐divinylbenzene(p‐DVB). The radical copolymerization of this macromer with styrene(St) or MMA was carried out in benzene at 60°C and the reactivity ratio of both monomers (r2) was calculated from a kinetic scheme of copolymerization. As a result, the effect of molecular weight and concentration of macromers was not observed in both copolymerization systems. The value of r2, however, decreased as the number of end vinyl groups in a macromer (N) increased. These results are discussed in some detail as we describe the construction of the kinetic model of copolymerization.
Polyimides from dianhydrides and bis(p‐aminophenyl) alkane diamines. I
Authors: Ghatge N. D. , Shinde B. M. , Mulik U. P. 
Published: April 2003

AbstractPolyimides were synthesized from pyromellitic dianhydride (PMDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and three different diamines with the following general structure:
magnified image
where R is ethyl, propyl, or isobutyl. The poly(amic acids) obtained had inherent viscosities ranging from 0.30 to 0.93 and were thermally/chemically converted to polyimides. The thermal stability of the polyimides was evaluated by using dynamic thermogravimetric analysis in air. Physical and thermal properties of these polyimides were compared with that obtained by reacting 2,2‐bis(4‐aminophenyl) propane and PMDA/BTDA.
Transcrystallinity in polypropylene
Authors: Huson M. G. , McGill W. J. 
Published: April 2003

AbstractA study using hot‐stage microscopy and differential scanning calorimetry in assessing the ability of a number of substrates to nucleate transcrystalline growth in polypropylene is reported. Surface energy, chemical composition, crystal morphology, and moisture content of the substrate are discounted as being of importance in determining the ability of a substrate to nucleate polypropylene. It is concluded that surface topography plays a major role and it is argued that a prealignment of polymer chains occur in suitably sized cracks or channels on the surface. The rate of cooling the melt also dramatically influences the nucleating activity of a surface and this is ascribed to interfacial stresses resulting from differential contraction.
DSC studies of phase transitions in poly(diethylsiloxane)
Authors: Papkov V. S. , Godovsky Yu. K. , Svistunov V. S. , Litvinov V. M. , Zhdanov A. A. 
Published: April 2003

AbstractThe differential scanning calorimetry studies have shown that high‐molecular linear poly(diethylsiloxane) can exist in two high‐temperature polymorphs which melt at 280 and 290 K. The heats of fusion of the high‐temperature polymorphs are 17 and 21 J/g, respectively. Each of the high‐temperature forms arises from the corresponding low‐temperature form the corresponding low‐temperature form when the polymer is heated: the first at 214 K (transition heat is 28 J/g) and the second at 206 K (transition heat is 26 J/g). The mesophase formed from the molten high‐temperature crystalline phases melts in a rather broad temperature range of 290 to 327 K, and the heat of this transition is 2.7 J/g. Crystallization of poly(diethylsiloxane) from the mesomorphic and the supercooled amorphous state is different. In the first case, apparently, the whole mesophase is converted to the crystalline phase and the samples have a crystallinity near 1. In the second case the crystallinity is only ca. 0.3. The temperature range in which the mesophase melts depends on the molecular weight of the polymer, presence of crosslinks and the conditions under which it has been formed, e.g., temperature.
Study of copolymer–copolymer interactions and formation of intermacromolecular complexes
Authors: Chatterjee S. K. , Malhotra A. , Yadav D. 
Published: April 2003

AbstractInterpolymer complex formation has been studied between methacrylic acid‐methacrylamide copolymer and acrylic acid–acrylamide copolymer. The respective co‐monomer units of the two copolymers enter into complex formation through H‐bonding and ion dipole interactions. The unreacted units in the copolymer complex also interact with homopolymers such as PEO and PVP to form ternary complex. Formation of complexes and replacement reactions could be shown through several experimental techniques, e.g., viscometry, conductometry, and potentiometry.
Modification mechanism in olefin polymerization catalysts TiCl4/MgCl2–aromatic ester–Al(C2H5)3
Authors: Kissin Y. V. , Sivak A. J. 
Published: April 2003

AbstractAn IR/UV study of the interaction between ethyl benzoate and Al(C2H5)3 in dilute heptane solution at 25–75°C demonstrated that the ester is readily reduced under these conditions with the formation of two aluminum dialkyl alkoxides, Al(C2H5)2 and Al(C2H5)2OC(C2H5)2C6H5, as major products. Rate constants of the reduction of the initial AI(C2H5)3 · ester complex by free AI(C2H5)3 are 2.9 (26°C), 14.4 (50°C), and 59.6 (75°C) L/mol min; Eact = 52.0 kj/mol. Study of propylene polymerization with this catalytic system at 50°C showed that preliminary aging of the AI(C2H5)4–ethyl benzoate mixtures at 25°C for 24 h and at 50°C for 2 h does not adversely affect catalyst performance. These data suggest that the possible actual modifier in this catalytic system is aluminum alkoxide with a highly branched tertiary alkoxy group.
Preparation of polysiloxanes from silicic acid. VII. Effects of the degree of esterification and alkyl groups on condensations of silicic acid esters and formation of fibrous silica
Authors: Abe Yoshimoto , Shintani Nobuhiro , Misono Takahisa 
Published: April 2003

AbstractSilicic acid esters were prepared by the reaction of the silicic acid in tetrahydrofuran with various alcohols such as such as methanol, ethanol, 2‐propanol, 1‐butanol, 2‐methyl‐2‐propanol and 1‐octanol, using an esterification apparatus designed especially to allow the preparation of silicic acid esters from alcohols with low boiling points or appreciable steric hindrance. With the intent of obtaining a spinnable ester solution by condensation of silicic acid esters, the effects of the degree of esterification (DE) and alkyl group on gel time and spinnability are investigated. An increase in the DE and the size of the alkyl group led to an increase in the gel time of the esters. Esters solutions with a good spinnability were prepared from n‐butyl and isopropyl esters with DEs of 40–50%. In addition, the gel permeation chromatography of condensing esters with low DEs showed a rapid increase in molecular weight. The results showed that spinnability depended on DE and the ester's alkyl group. Fibers could be formed with length of about 10–100 cm from ethyl, isopropyl, and n‐butyl esters with DEs 40–50% and with length of 10 cm from octyl ester with DE 26%.
Long‐lived polymer radicals. VI. Polymerization of N‐methylmethacrylamide with formation of living propagation radicals
Authors: Sato Tsuneyuki , Miyamoto Jiro , Otsu Takayuki 
Published: April 2003

AbstractThe polymerization of N‐methylmethacrylamide (NMMAm) with azobisisobutyronitrile (AIBN) was investigated kinetically in benzene. This polymerization proceeded heterogeously with formation of the very stable poly(NMMAm) radicals. The overall activation energy of this polymerization was calculated to be 23 kcal/mol. The polymerization rate (Rp) was expressed by: Rp = k[AIBN]0.63‐0.68[NMMAm]1−2.5. Dependence of Rp on the monomer concentration increased with increasing NMMAm concentration. From an ESR study, cyanopropyl radicals escaping the solvent cage were found to be converted to the living propagating radicals of NMMAm in very high yields (ca. 90%). Formation mechanism of the living polymer radicals was discussed on the basis of kinetic, ESR spectroscopic, and electron microscopic results.
Aromatic polyamides. XI. Effect of the halogen substitution on the thermal and flammability behavior of poly(1,4‐phenylene terephthalamide)
Authors: Kapuscinska M. , Pearce E. M. 
Published: April 2003

AbstractThis article concerns the synthesis and characterization of poly(1,4‐phenylene terephthalamide) and halogenated derivatives thereof. It was found that the halogen substitution affected significantly the thermal characteristic and flame resistance of that polyamide. In a nonoxygen atmosphere two‐step decomposition process for the halogenated, while only one‐step for unsubstituted polyamides were observed. The results supported the previous suggestion, that in the case of the halogenated polyamides the char yield enhancement and the flame resistance improvement are associated with halogen release and ring‐forming reactions during their pyrolysis.
Reactivities of carboxylic acid vinyl monomers differentiated by the aggregation forms and their simple molecular orbital interpretation
Authors: Kuzuya Masayuki , Kawaguchi Tohru , Daikyo Toshiya , Okuda Takachiyo 
Published: April 2003

AbstractPlasma‐exposed solution polymerizations of carboxylic acid vinyl monomers [methacrylic acid (MAA) and acrylic acid (AA)] in carbonyl solvents were found to be highly efficient, particularly in high‐temperature postpolymerizations. Thermal polymerizations in these solvents were also accelerated to a considerable extent. Obviously the carbonyl solvents and/or the increased temperature caused the monomer aggregates to accelerate the rate of polymerization.The molecular orbital features of the simple models of monomer aggregates, that is, the monomeric form, singly hydrogen bonded open‐dimer and doubly hydrogen bonded cyclicdimer of MAA and AA, supported by the CNDO/2 method, were capable of distinguishing the variations in the reactivities of the aggregates; the open‐dimer was shown to be responsible for the enhanced reactivities under the abovementioned conditions.