bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of t‐butyl thiirane. I. Stereoelective polymerization of the racemic monomer
Authors: Dumas Philippe , Spassky Nicolas , Sigwalt Pierre 
Published: April 2003

AbstractThe stereoelective polymerization of racemic t‐butyl thiirane was performed with chiral zinc glycolate. Monomers and polymers of high optical purities were isolated. A new kinetic scheme in which the ratio of the rates of consumption of both enantiomers obeys a second‐order relationship is proposed. This behavior is different from that observed for other three‐membered ring monomers.
Photocrosslinking of elastomer systems. I. UV light‐induced reactions in a blend of EPDM‐benzoin derivatives
Authors: Bousquet Jean‐Alain , Faure Jean , Fouassier Jean‐Pierre , Donnet Jean‐Baptiste , Haidar Bassel , Vidal Alain 
Published: April 2003

AbstractPhotocrosslinking experiments were performed on elastomeric polymer films (EPDM) that contained benzoin derivatives as photosensitive initiators. Infrared (IR) and ultraviolet (UV) spectroscopy investigations were used in conjunction with physical property measurements. The results all together make it possible to discuss the crosslinking mechanism and pose interesting questions about the reactivity of benzoin derivatives in their excited states in relation to their efficiency in the crosslinking process.
Graft copolymers containing nucleic acid bases and L‐α‐amino acids
Authors: Overberger C. G. , Inaki Yoshiaki 
Published: April 2003

AbstractGraft copolymers of nucleic acid bases and L‐α‐amino acids on polyethyleneimine were synthesized, and carboxyl derivatives of adenine and thymine were grafted by the p‐nitrophenyl ester method onto linear and branched polyethyleneimine. The carboxyl derivatives of nucleic acid bases were also grafted onto the monomeric graft copolymers of L‐α‐amino acids on polyethyleneimine; the carboxyl derivatives were obtained by the condensation of polyethyleneimine with L‐α‐amino acids with a coupling agent.
Radiation‐induced copolymerization of methyl trifluoroacrylate with propylene
Authors: Matsuda Osamu , Watanabe Terutaka , Tabata Yoneho , Machi Sueo 
Published: April 2003

AbstractCopolymerization of methyl trifluoroacrylate (MTFA) with propylene in bulk was induced by γ irradiation. A wide range of the initial monomer composition gives an equimolar alternating co‐polymer. The reactivity ratios of r1 (MTFA) and r2 (propylene) were determined to be 0.01 and 0.005, respectively. The polymerization rate at an equimolar monomer composition is proportional to the 1.0 power of the dose rate. The dose rate dependency of higher than 0.5 may be ascribed to unimolecular termination due to a degradative chain transfer of propagating radicals to propylene. The G values of the initiating radical formation and the polymerization reaction were calculated to be 1.78 and 1336, respectively. The dependence of the copolymerization rate on the temperature was small, and the activation energy of copolymerization was 1.1 kcal/mole from −6 to 50°C.
Poly(β‐Amino acids). V. Synthesis and conformation of oligomeric α‐isobutyl‐L‐aspartate
Authors: Yuki Heimei , Okamoto Yoshio , Doi Yuichi 
Published: April 2003

Abstractα‐Isobutyl‐L‐aspartate oligomers, Z‐(α‐i‐Bu‐Asp)2n–OEt (n = 1–5), where Z = benzyloxycarbonyl and OEt = ethyl ester, were prepared stepwise, and their conformation in solution was investigated by optical rotation, circular dichroism (CD), and NMR spectroscopy. The oligomers up to hexamer existed only in a disordered form. An ordered structure began to appear at octamer and decamer in chloroform and 2,2,2‐trifluoroethanol. The ordered structure was more favorable for N‐unprotected oligomers, H‐(α‐i‐Bu‐Asp)2n–OEt, in comparison with the corresponding Z‐(α‐i‐Bu‐Asp)2n–OEt. The effects of oligomer concentration and temperature on the structure were slightly observed. The most likely ordered structure was a β form caused by intramolecular association.
Higher aliphatic aldehyde polymers. VI. Poly(n‐nonaldehyde)
Authors: Starr J. , Vogl O. 
Published: April 2003

AbstractCrystalline poly(n‐nonaldehyde) (PNA) was prepared by anionic polymerization of n‐nonaldehyde (NA) in methylcyclohexane (MCH) with lithium tertiary butoxide (LTB) as the initiator. Normal low‐temperature conditions did not give polymer reprodusibly; however, when the polymerization was carried out with a gradual temperature decrease to −60°C holding at this temperature followed by completion at −78°C, a moderate yield of PNA was obtained. The polymer was acetate capped and characterized. Infrared and PMR spectroscopy, as well as degradation of the polymer in the presence of 2,4‐dinitrophenylhydrazine to the hydrazone, conclusively proved the chemical structure of the polymer. VPO measurements and measurement of the inherent viscosity showed the polymer to be of moderate molecular weight. PNA is highly crystalline and shows two transition regions, one corresponding to the melting of the main chain at temperatures above 120°C and one region between 50 and 80°C, which is related to the crystallization of the aliphatic side chains. PNA, although inherently brittle, can be extruded through an orifice at a temperature near the side‐chain melting temperature to give an extrudate whose x‐ray patterns show the characteristics of a fiber diagram. It is suggested that the crystal structure of the PNA is similar to that of poly(n‐heptaldehyde) but with a larger a spacing, which is expected from a longer aliphatic side chain.
The stereoregularity of polystyrenes obtained by different ion pairs of polystyryl alkali salts
Authors: Uryu Toshiyuki , Kawamura Tokiji , Matsuzaki Kei 
Published: April 2003

AbstractThe stereoregularity of polystyrenes obtained with sodium, potassium, rubidium, and cesium naphthalenes in various solvents was determined by 13C‐NMR spectroscopy. Polystyrenes produced by contact ion pairs of polystyryl cesium in dioxane and tetrahydrofuran (THF) had the proportions of a 57–58% racemic dyad (Pr), whereas the Pr values increased to 65 and 69% by solvating Cs+ counterions in dimethoxyethane and by agent‐separating them with crown ether, respectively. Polystyrene obtained by contact ion pairs of polystyryl sodium in dioxane showed a Pr of 66%; polymers produced by solvent‐separated ion pairs of polystyryl sodium in THF at −78°C had a Pr of 71%. A polymerization system which contained alkali counterions with large ionic radii and solvents with low dielectric constants in which only contact ion pairs existed produced polystyrenes with isotactic‐rich configurations. The stereoregularity of polystyrene produced by contact ion pairs of polystyryl potassium and rubidium in tetrahydropyran (THP) occurred intermediately between that of polymers obtained in diethyl ether and THF. It was concluded that the stereoregulation of contact ion pairs may be closely related to the interionic distance of the ion pair.
Modification of properties of ion exchange membranes. VII. Relative transport number between various cations of cation exchange membrane having cationic polyelectrolyte layer and mechanism of selective permeation of particular cations
Authors: Sata Toshikatsu , Yamane Reiichi , Mizutani Yukio 
Published: April 2003

AbstractElectrodialytic behavior of cation exchange membrane having cationic polyelectrolyte layer on its surface (relative transport number between two cations, P, current efficiency, and electric resistance of the membrane during the electrodialysis) was measured using various cations, and the mechanism of selective permeation of lower‐valent cations than the higher and of larger hydrated cations than the smaller was investigated. The following conclusions were obtained: (1) the cationic polyelectrolyte layer narrowed the pathway for ions; (2) when the pathway was made narrower by other methods, the remarkable change of the permselectivity of the membrane did not occur; (3) the effectiveness of the cationic polyelectrolyte layer was depressed by the treatment with anionic polyelectrolytes to neutralize the cationic charge on the membrane surface; and (4) the cation with larger hydrated diameter (potassium ions) more easily permeated through the membrane having the polyelectrolyte layer than that with the smaller hydrated diameter (sodium ions). It is concluded that the change of P by the cationic charge layer on the membrane surface is based on the difference in the strength of the electrostatic repulsion between two cations against the cationic charge layer.
Changes in row structure of extruded polyethylene film on grafting with styrene. I. Distribution of polystyrene and crystalline reorientation
Authors: Ungar G. 
Published: April 2003

AbstractExtruded films of linear polyethylene were grafted with styrene in a 1:2 styrene‐‐‐methanol solution and pure styrene. The reaction was induced by simultaneous γ irradiation. Crystallinity of polyethylene was hardly affected by a polystyrene‐to‐polyethylene ratio as high as 13.5. From the anisotropy of film growth and small‐angle x‐ray diffraction it was concluded that polystyrene incorporated both into intercrystalline layers and newly formed domains alongside the stacks of lamellae. The proportion of polystyrene in interlamellar layers depends on the length of grafted chains; that is, on grafting conditions. A higher than expected proportion of occluded homopolystyrene was found in films grafted in methanol solution. The glass transition temperature of polystyrene decreased with grafting yield. Grafting in methanol solution produced changes in the x‐ray orientation pattern of polyethylene. This was ascribed to untwisting and straightening crystalline lamellae in the row nucleated cylindrites.
Copolymerization of carbon dioxide and propylene oxide with supported diethylzinc catalysts
Authors: Soga Kazuo , Hyakkoku Kyoko , Ikeda Sakuji 
Published: April 2003

AbstractDiethylzinc was allowed to react with various metal oxides in n‐heptane at 60°C, and the copolymerization of propylene oxide and carbon dioxide was investigated at 60°C in solution in dioxane with reaction products as catalysts. An alternate copolymer was obtained with every catalyst, but the yield of copolymer and the number‐average molecular weight depended significantly on the supporting materials. In a kinetic study of the copolymerization we found that the catalytic efficiency (number of propagating species per number of zinc supported) was only a few percent with every catalyst. The copolymerization was also examined by using several kinds of silica, whose pore diameters are markedly different, as supports. The results obtained strongly suggested that only the active species existing in large pores act as the propagating species.
Molecular weight of polystyrene polymer obtained in the emulsion polymerization at low monomer concentration and the harkins–smith–ewart–gardon (HSEG) theory
Authors: Chatterjee Shankar P. , Banerjee Monoranjan , Konar Ranajit S. 
Published: April 2003

AbstractThe shape of the yield–time curves in the emulsion polymerization of styrene is a function of the recipe composition. Three types of yield–time curve were observed: (1) sigmoidal, (2) linear from the onset of polymerization, and (3) concave to the time axis; that is, the rate falls off continuously from the outset of polymerization. The viscosity‐average molecular weights (M̄v) of the polymers in a given run are approximately parallel to the average rate of polymerization [i.e.,(yield of polymer at time t)/(time t)]. The Harkin–Smith–Ewart–Gardon (HSEG) theory provides a qualitative description of the emulsion polymerization of styrene at low monomer concentration if the yield–time curve is sigmoidal. From Gardon's equations it is found that the average number of radicals per particle (Q) varies from 0.5 to 2.0, depending on the composition of the recipe. The (M̄v)expt/(M̄v)calc ratio lies between 1 and 2. The termination/propagation rate constant (kt/kp) ratio is a function of the composition of the recipe at a given temperature of polymerization and varies from 0.78 to 11.5 when it is estimated from the experimental data. The theoretical value, however, is 117.0. It has been shown that for a polydisperse system with particles of radius (r) between 10 and 1000 Å the maximum number of latex particles (N1)/ml of the aqueous phase would be 1019–1013; that is, if 10 ≤ r ≤ 1000 Å, then 5.97 × 1019 ≥ N1 ≥ 5.97 × 1013/ml.
The crystallization characteristics of ethylene block copolymers
Authors: Hay James N. , Wiles M. 
Published: April 2003

AbstractBlock copolymers of ethylene and butadiene with short ethylene sequences and degrees of polymerization up to 250 have been studied calorimetrically to determine their structure in the melt and also on crystallization. Crystallization rate characteristics and the thermodynamic parameters of the melting of block copolymers were studied. Block copolymers with ethylene sequences with degrees of polymerization below 20–30 were amorphous. Those with ethylene sequences of 35–45 units crystallized with extended chain crystals; above 45 units the polyethylene blocks crystallized with chain folding. There was a corresponding reduction in the melting point of the crystals and in the surface free energy of the crystals. The extent of crystallinity that developed within the copolymers was dependent on crystallization temperature and independent of time. This behavior was unlike that exhibited by polyethylene samples of similar molecular weight and was considered due to the effect of phase separation of the two blocks in the melt and nucleation control of the crystallization of the isolated domains. Analogous behavior was observed with polyethylene for polymer blends with polystyrene.
Effect of catalysts on asymmetric induction cationic copolymerization of l‐menthyl vinyl ether with indene
Authors: Kurokawa Masahiro , Yamaguchi Hidemasa , Minoura Yuji 
Published: April 2003

AbstractCationic copolymerization of l‐menthyl vinyl ether (l‐MVE) with indene (IN) was carried out with several catalysts in toluene (Tol) at 0°C. The catalysts used were BF3OEt2, CH3COClO4, and SnCl4. l‐Menthyl residue, an optically active side chain of the copolymer obtained, was removed with dry hydrogen bromide gas by the ether cleavage reaction. Ether‐cloven copolymers [vinyl alcohol(VA)–IN] also had optical rotation. The efficiency of asymmetric induction to the polymer main chain was in the order of BF3OEt2 > CH3COClO4 > SnCl4.
The effect of solvents on asymmetric induction cationic copolymerization of l‐menthyl vinyl ether with indene
Authors: Kurokawa Masahiro , Yamaguchi Hidemasa , Minoura Yuji 
Published: April 2003

AbstractCationic copolymerization of l‐menthyl vinyl ether (l‐MVE) with indene (IN) was carried out in several solvents with BF3OEt2 as catalyst at 0°C. The solvents used in this study were selected toluene (Tol), chloroform (CHCl3), chlorobenzene (BzCl), 1,2‐dichloroethane (EtCl2), and nitrobenzene; (BzNO2)/Tol = 65/35 mixture solvent. l‐Methyl residue, which is an optically active side chain of copolymer produced by cationic copolymerization, was removed with dry hydrogen bromide gas by ether cleavage reaction. The copolymer [vinyl alcohol(VA)–lN], produced by the ether cleavage reaction, also showed optical rotation. From this result, therefore, it was concluded that asymmetric induction takes place in the copolymer main chain. The efficiency of asymmetric induction was determined by the measurement of optical rotation of VA–IN copolymer after the ether cleavage reaction. The efficiency of asymmetric induction in the copolymer main chain developed from the variation on polymerization solvents; the order was Tol > EtCl2 > BzCl > CHCl3 > BzNO2/Tol (65/35) mixture solvent.
Block copolymers of copolyamides with polyoxirane
Authors: Masař B. , Čefelín P. , Šebenda J. 
Published: April 2003

Abstract1,n‐Diaminopolyamides, based on lactams (P1), gave by reaction with isocyanate‐group‐terminated polyoxirane macromers (P2) in solution at ambient temperature, the copolymers of (P1 – P2)y type with y = 5–10 and solution viscosity ηred = 1–11 dl/g in high yields. The composition of copolymers (40–80% of P1) was found by elemental analysis and confirmed by the 1H‐NMR method. A substantial chain extension was observed in the reaction of macromers with low‐molecular‐weight “couplings.”
New processable polyaromatic ether‐keto‐sulfones curable by intramolecular cyclization. XV
Authors: Lin Shiow‐Ching , Marvel C. S. 
Published: April 2003

AbstractNew processable polyaromatic ether‐keto‐sulfones were prepared from 2,2′‐diiododiphenyl‐4,4′‐dicarbonyl dichloride (I), bis(p‐phenoxybenzene)sulfone (II), isophthaloyl chloride (III), and diphenyl ether (IV) in Friedel–Crafts‐type polymerizations. In the most promising of the iodine‐containing polymers phenylacetylenyl groups were introduced in place of iodine. This polymer, with an initial monomer ratio of I:II:III:IV = 1:5:7:3, was further investigated. It is soluble in DMF, DMA, pyridine, and sulfuric acid. After curing it was insoluble in all solvents used and lost only 1.1% of its weight at 300°C when heated in air for three days. Hence in this cured state it has excellent chemical and thermal resistance. It can be cast into a film from solution in DMAc and a glass fiber laminate is readily prepared. The film is tough, transparent, and brown in color. The cured film is tougher than the uncured. The glass fiber laminate is also tough and fairly flexible. A distinct advantage of this type of polymer is its ready availability in relatively cheap raw materials. The phenylacetylenyl‐group‐containing polymer showed a transition temperature at 175°C and two exotherm peaks at 243 and 361°C which disappeared after curing in a DSC thermogram. Before and after curing this polymer displayed softening temperatures at 149 and 171°C, respectively, measured by a Vicat apparatus at a heating rate of 1°C/min. No melting temperatures up to 500°C were observed for any of the polymers in this study.
Soluble and curable prepolymers from polyallyl ester monomers containing aromatic imide groups
Authors: Tamamura Toshiaki 
Published: April 2003

AbstractFive polyallyl ester monomers that contain aromatic imide groups were synthesized as thermally stable laminating resins. From these monomers soluble and low‐melting prepolymers were obtained by radical polymerization in aprotic polar solvents such as N,N‐dimethylacetamide, N,N‐dimethylformamide, or N‐methyl ‐2‐pyrrolidone. The prepolymers are oligomeric compounds in which DP = 3–6 and have lower melting points than the corresponding monomers. It is assumed that the reaction of solvent molecule participates in the polymerization. Whereas, the bulk and the solution polymerization in n‐butyl acetate or n‐propyl alcohol yielded insoluble and infusible polymer. The relatively low‐melting prepolymers were curable at 150–180°C without the evolution of volatile by‐products. Resulting glass‐fiber laminates have no glass transition point below 300°C and thermooxidative stability at 330°C.
Electron spin resonance study on polymerization of alkyl acrylates with n‐butyl titanate(IV)–triethylaluminum catalyst
Authors: Hiraki Katsuma , Ikeda Shigeru , Kaneko Shoichi , Hirai Hidefumi 
Published: April 2003

Abstractn‐Butyl titanate(IV)–triethylaluminum catalyst at Al/Ti molar ratios greater than 6 polymerizes methyl and n‐butyl acrylates at −78°C. The polymerization system which includes methyl acrylate at −78°C, gives two ESR signals with g factors of 1.958 and 1.961 that overlap each other. The absorption intensity of the latter signal is approximately proportional to the polymer chain concentration calculated from polymer yield and the molecular weight. The polymerization system at Al/Ti ratios smaller than 3 has no catalytic activity on the polymerization and shows only the ESR signal with the g factor of 1.958. On the basis of these facts the ESR signal with the g factor of 1.961 is attributed to the active growing end of poly(methyl acrylate) with this catalyst. The character of this active growing end is discussed.
Direct polycondensation of nylon salts by polyphosphates and imidazole
Authors: Ogata Naoya , Sanui Kohei , Harada Masashi 
Published: April 2003

AbstractDirect polycondensation of various nylon salts (salts of dicarboxylic acid and diamine) took place under mild conditions in the formation of polyamide in the presence of polyphosphates and organic bases. Among organic bases imidazole was the best in terms of polymer yields. The reactivity of the polyphosphates was arranged in following order: pyrophosphate ≅ tripolyphosphate > tetrapolyphosphate. Otimum reaction conditions were investigated in terms of solvents, temperatures, and concentration of monomers. A reaction mechanism was proposed for the phosphorylation reaction, due to polyphosphates, which led to the direct polycondensation of nylon salts.
Monomer‐isomerization oligomerization of 2‐ethyl‐1,3‐butadiene by acid catalysts
Authors: Higashimura Toshinobu , Hasegawa Hiroshi 
Published: April 2003

AbstractThe cationic oligomerization of 2‐ethyl‐1,3‐butadiene (2EBD) by a superacid (CF3SO3H) and a superacid derivative (CH3COClO4) accompanied monomer isomerization to 3‐methyl‐1,3‐pentadiene (3MPD) before propagation to yield oligomers of the isomerized monomer as main products in benzene at 50°C. Detection of 3MPD in the reaction mixture and 1H‐NMR structural analysis of the produced oligomers confirmed the occurrence of this “monomer‐isomerization oligomerization.” On the other hand, in the presence of a metal halide catalyst (BF3OEt2) 2EBD reacted without isomerization and yielded oligomers that were different from those produced by the foregoing superacid catalysts. Monomer isomerization was suppressed in a polar solvent [(CH2Cl)2] or at lower temperatures. The mechanism of the oligomerization with monomer isomerization was discussed.
Low‐molecular‐weight species from high‐pressure polyethylene
Authors: Von Dohlen W. C. , Wilson T. P. 
Published: April 2003

AbstractA partial analysis is given of the low‐molecular‐weight “oil” fraction produced in the high‐pressure free‐radical–initiated polymerization of ethylene. These oils are shown to constitute a separate family of compounds whose molecular weight distribution can be clearly distinguished from that of the remainder of the polymer. The mechanisms of formation of oils as a class, and of individual compounds found in the oil fraction, are discussed in some detail. The structures of the oils are used to inter steps in the mechanism of polymerization that lead to the formation of short‐chain branches and unsaturation. It is concluded that the data are consistent with the extended Roedel mechanism with the provisions that (1) secondary radicals are probable products of radical scission, (2) cyclic intermediates of other than six members lead to the formation of three, five, and possibly six carbon branches, and (3) clusters of ethyl groups separated by single methylene groups are unlikely side chains.
Kinetics of imidization and crosslinking in PMR polyimide resin
Authors: Lauver Richard W. 
Published: April 2003

AbstractInfrared spectroscopy and differential scanning calorimetry were used to study the imidization and crosslinking kinetics of norbornenyl‐capped addition type of polyimide resins (designated PMR for polymerization of monomer reactants). The spectral and thermal analyses were performed on resin specimens that had been isothermally aged at temperatures appropriate for imidization (120–204°C) and crosslinking (275–325°C). Imidization occurs rapidly (about 10−2 min−1) at short times, but, at times longer than about 0.5 hr, the rate decreases significantly (about 10−4 min−1). The crosslinking reaction exhibits first‐order kinetics during the initial part of the reaction, and its rate appears to be limited by the reversion of the norbornenyl Diels‐Alder adduct. Both the first‐order dependence and the activation energy (about 44 kcal) are consistent with this interpretation. The total heat evolved per mole of end cap during crosslinking shows an inverse dependence on the molecular weight of the imido prepolymers. This reflects the effect of end‐cap dilution and decreased mobility of the larger oligomers.