bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of copolyesters of PET and substituted p‐hydroxybenzoic acids
Authors: Balachandar M. , Balakrishnan T. , Kothandaraman H. 
Published: April 2003

AbstractRandom copolyesters of different compositions were synthesized by melt polycondensation of poly(ethylene terephthalate) and 3‐bromo ‐ and 3,5‐dibromo‐p‐hydroxybenzoic acids. The copolymer compositions were determined by proton nuclear magnetic resonance spectroscopy. The thermal behavior of these copolyesters was investigated by differential scanning calorimetry. The glass transition temperature, crystallization temperature, and decomposition temperature were found to increase with increase in the paraoxybenzoate content of the copolyesters. The limiting viscosity number and the weight‐average molecular weight were determined.
Photodegradation of polyvinylacetophenone. I. Long‐wave photolysis
Authors: Weir N. A. , Milkie T. H. 
Published: April 2003

AbstractPolyvinylacetophenone (PVAP) films were exposed to long‐wave (λ ≥ 300 nm) ultraviolet radiation in the absence of oxygen. The gaseous products, determined quantitatively by mass spectrometry, were methane, ethane, carbon monoxide, and acetaldehyde. These indicated that the polymer was undergoing photodecomposition via a Norrish type I reaction. The polymer also undergoes crosslinking reactions, becoming insoluble after 100 hr irradiation, and the ultraviolet and phosphorescence spectra indicate loss of carbonyl chromophores. The mechanism of photolysis is discussed, and the implications of the effects of photodegradation on the efficiency of the polymer as a sunlight energy transfer agent are examined.
Synthesis, characterization, and polymerization of N‐vinylarylamines
Authors: Lin John W‐P. 
Published: April 2003

AbstractSeveral N‐vinylarylamines have been prepared by direct N‐vinylation of arylamine salts with acetylene at atmospheric pressure. Nuclear magnetic resonance (NMR) spectra of the various N‐vinylarylamines were recorded and chemical shift assignments were made for the first time. The vinyl protons of the enamines generally exhibit an ABX pattern. The electron‐rich monomers are sensitive to acid‐catalyzed hydrolysis in a wet solvent. Polymerizations of the monomers were carried out at low temperatures with phosphorous pentafluoride as an initiator. It was found that PF5 generated directly from thermal decomposition of p‐chlorobenzenediazonium hexafluorophosphate is useful in the preparation of an extremely high‐molecular‐weight poly(N‐vinylcarbazole) (Mw = 3 × 106) with a narrow molecular weight distribution (MWD = 2.1). The polymerizability of N‐vinylarylamines appears to vary with the amine functional groups of the monomers. N‐vinylarylamine containing a planar amine moiety such as carbazole forms a higher‐molecular‐weight polymer than the monomers with the nonplanar bulky amine groups.
Contribution to the mechanism of copolymerization of phenylvinyl alkyl ethers and thioethers with maleic anhydride
Authors: Vuković R. , Kurešević V. , Fleš D. 
Published: April 2003

AbstractThe equilibrium constants of the charge‐transfer complex monomers of phenylvinyl alkyl ethers (I) and thioethers (II) with maleic anhydride (MAn) were determined by the transformed Benessi—Hildebrand NMR method, and it was found that the bulkiness of alkyl groups had no significant influence on the equilibrium constant. The rate of copolymerization, however, was largely dependent on the bulkiness of the alkyl groups in the phenylvinyl alkyl ether series. The rate of copolymerization of I (R = Et; sec‐Bu) and II (R = Et; sec‐Bu) with MAn was proportional to the square root of AIBN concentration, and intrinsic viscosity of poly‐I (R = Et)‐co‐MAn was proportional to the reciprocal square root of AIBN concentration. Spontaneous copolymerization did not occur, but I (R = Et) copolymerizes with MAn in the presence of oxygen; II did not copolymerize with MAn in the presence of oxygen; nor in the presence of peroxide initiators. In the copolymerization of I (R = Et) and MAn, it was found that molecular weight increases with conversion. By applying the generalized model described by Shirota and co‐workers, the reactivity ratios k1c/k12 and k2c/21 for copolymerization of I (R = Et) and II (R = Et) with MAn were calculated from the change of copolymerization rate with monomer feed at constant total monomer concentration.
Quaternary ammonium polyelectrolytes. III. Kinetic studies of amination of chloromethylated polystyrene with tertiary amines
Authors: Luca Cornelia , Petrariu I. , Dima M. 
Published: April 2003

AbstractThe amination kinetics of benzyl chloride and chloromethylated polystyrene with three tertiary amines were studied: N‐2‐hydroxyethyl‐dimethylamine, N,N‐bis(2‐hydroxyethyl)‐methylamine, and triethylamine in N,N‐dimethylformamide. The amination of chloromethylated polystyrene takes place with two reaction rate constants K1 and K2. K2 is higher than K1; hence there is a self‐accelerating effect. This phenomenon is due to the influence of the positive electrostatic field of the macroion chain on amines that are nucleophilic reactants. The magnitude of the self‐accelerating effect given by the K2/K1 ratio depends on the substituent volume of the nitrogen atom of the amine molecule.
Coenzyme models. 19. Oxidation of furoin by a flavin immobilized in cationic polyelectrolytes: A flavoenzyme model
Authors: Shinkai Seiji 
Published: April 2003

AbstractThe rate constants for the oxidation of furoin by a flavin (vitamin B2 analog) immobilized in cationic polymers were evaluated under anaerobic conditions, and the influence of reaction environments was discussed in connection with the enzymatic reactivity. It was found that (1) proton abstraction from furoin which forms the carbanionic intermediate is rate determining in the initial stage of the reaction and is facilitated by the environment of cationic polymers, (2) proton abstraction is efficiently accelerated by added cationic surfactant (CTAB), and (3) N‐dodecylbenzohydroxamic acid in aqueous CTAB acts as an excellent proton‐abstracting reagent. The polymers with high dodecyl group content served, in all cases, as better oxidizing reagents. As a summary of these conclusions, the importance of hydrophobic environments in flavin‐mediated oxidation was emphasized.
Hydrolysis of dextrin in the presence of block copolymer of vinyl alcohol and styrenesulfonic acid
Authors: Arai Kenichiro , Ogiwara Yoshitaka 
Published: April 2003

AbstractA block copolymer of vinyl alcohol and styrenesulfonic acid was prepared by a two‐step polymerization and subsequent modification, and its catalytic activity on the hydrolysis of dextrin was investigated. The hydrolysis rate in the presence of the copolymer containing more vinyl alcohol‐repeating units was found to follow Michaelis–Menten‐type kinetics, whereas that in the presence of a copolymer containing fewer vinyl alcohol units proceeded according to ordinary second‐order kinetics. The process of complex formation for the former system was characterized by pronounced decreases in enthalpy and entropy, although the enthalpy and the entropy of activation for the decomposition of the complex to product was comparable to that of a sulfuric acid‐catalyzed system. The maximum rate enhancement obtained in the present experiment was approximately fivefold on the basis of the reaction in the presence of sulfuric acid at 65°C. The results were compared with those obtained in the presence of a random copolymer catalyst, previously reported.
Polymerization of acetylene and its monosubstitutes in the presence of halides and oxohalides of molybdenum and tungsten
Authors: Voronkov M. G. , Pukhnarevich V. B. , Sushchinskaya S. P. , Annenkova V. Z. , Annenkova V. M. , Andreeva N. J. 
Published: April 2003

AbstractMoCl5, WCl6, and OMoCl4 were found to be effective initiators for the polymerization of acetylene and its monosubstituted derivatives RCCH. The polymerization proceeded in homogeneous and heterogeneous media and was carried out in nonpolar (chloroalkanes, aromatic hydrocarbons) and polar (THF, acetone, dioxane, carboxylic acids) solvents to give a high yield of polymers.
Polyimidines. VI. The comparison of polyimidines from bis(3,3‐diphenyl‐6‐phthalidyl) ketone
Authors: Cassidy Patrick E. , Doctor Shreenath V. 
Published: April 2003

AbstractNew thermally stable polyimidines have been synthesized from bis(3,3‐diphenyl‐6‐phthalidyl) ketone and five diamines: o‐phenylenediamine, m‐phenylenediamine, 1,5‐diaminonapthalene, 1,8‐diaminonapthalene, and benzidine. Polymers of low molecular weight (inherent viscosity up to 0.24 dl/g) were obtained by solution and sealed‐tube polymerizations. The structural differences of the amines provided information concerning the effects on the thermal stability properties of the resulting polyimidines. The yellow to black polymers exhibited a 10% loss ranging from 420–510°C in air and 460–555°C in nitrogen and were soluble in chloroform and dimethylformamide.
Photochemical reactions of N‐vinylcarbazole in the binary solvent of benzonitrile and nitrobenzene
Authors: Hamanoue Kumao , Teranishi Hiroshi , Okamoto Masami , Furukawa Yoh , Tagawa Seiichi , Tabata Yoneho 
Published: April 2003

AbstractPhotochemical reactions of N‐vinylcarbazole (VCZ) in the binary solvent of benzonitrile (ϕCN) and nitrobenzene (ϕNO2) were investigated. Both solvent and oxygen effects on the final products were examined. Benzonitrile and nitrobenzene behaved differently in the photochemical reaction of VCZ. At higher concentrations of benzonitrile in the aerated system, cyclodimerization was favored and it was inhibited by a cation scavenger and retarded by a radical scavenger. Polymerization occurred in the deaerated system and was inhibited by a radical scavenger and not by a cation scavenger. Using picosecond laser photolysis it was concluded that cyclodimerization occurs through the diffusion‐controlled encounter collision of the excited singlet state of VCZ with an oxygen molecule, producing the VCZ cation radical and oxygen anion radical, and that this oxygen anion radical plays a very important role in the cyclodimerization of VCZ. It was also suggested that radical polymerization in the deaerated system is initiated by the excited triplet state of VCZ. On the other hand, at higher concentrations of nitrobenzene, only cationic polymerization took place irrespective of the presence of oxygen, and it was suggested that a contact charge‐transfer complex is produced by the mixing of VCZ with ϕNO2 producing VCZ cation radical and NO2 anion radical by an excited‐state electron transfer.
Radiation degradation of methyl α‐chloroacrylate–methacrylonitrile copolymers
Authors: Chen Chi‐Yu , Pittman Charles U. , Helbert John N. 
Published: April 2003

AbstractThe radiation degradation behavior of methyl α‐chloroacrylate (MCA) and methacrylonitrile (MCN) copolymers has been investigated as part of a program to develop high‐sensitivity polymeric resists for integrated circuit manufacture. High‐molecular‐weight copolymers were prepared by emulsion techniques. Several different copolymer compositions were prepared varying from 19 to 68 mole % MCA. These copolymers were fractionated and then subjected to γ irradiation from a 60Co Source. The Gs ‐ Gs, Gs ‐ 4Gs values were determined from M̄;F>nk−1 and Gu−1 versus dose plots, and the Gfs and Gs Values were then calculated. Molecular weights of both unirradiated and irradiated polymers were analyzed by membrane osmometry and gel permeation chromatography. All copolymers exhibited higher degradation susceptibilities than that of poly(methyl methacrylate) (PPMA), which has Gx = 1.3. The individual Gx and Gx values of the copolymers were found to fall between those of the two homopolymers, poly(methyl α‐chloroacrylate) (Gx = 6.0) and polymethacrylonitrile (Gx ∼ 3.1). The dependence of Gx and Gx values on molecular weight was minor. The crosslinking susceptibility of the poly(methyl α‐chloroacrylate) (Gx ∼ 0.8), was greatly decreased by copolymerization with MCN. Relatively small amounts of MCN caused a large drop in Gx, i.e., Gx ∼ 0.15 at 32% MCN and Gx ∼ 0.03 at 51% MCN. The observation could be attributed to the decreasing probability that crosslinking sites, in the MCA monomer units on adjacent chains, would lie in close proximity.
Stereospecific polymerization of isobutyl vinyl ether catalyzed by calcined iron sulfate
Authors: Hino Makoto , Arata Kazushi 
Published: April 2003

AbstractThe polymerization of isobutyl vinyl ether was studied in a heterogeneous system using iron (II) sulfate calcined in air at various temperatures as a catalyst. The maximum activity was shown by the catalyst calcined at 700°C, which effected the polymerization at room temperature in a few seconds, while the sulfate treated at 750°C was totally inactive. Poly(vinyl ethyl ether) was also obtained by the FeSO4 (700°C) catalyst at room temperature. This catalyst formed the crystalline polymer (melting temperature 135–138°C) when the reaction was performed in toluene as solvent at room temperature. Poisoning experiments with Hammett indicators were carried out with the FeSO4 (700°C) catalyst. The treatment with n‐butylamine rendered it inactive in the reaction of isobutyl vinyl ether, while its catalytic activity was little affected by dicinnamalacetone. On the basis of the observed results, the nature of active sites of catalyst is discussed.
State of order in isotactic polyhexylethylene
Authors: Trafara Gundolf 
Published: April 2003

AbstractCooling slowly from the melt and annealing at 250 K for a month isotactic polyhexylethylene becomes partially crystalline. The degree of crystallinity, calculated according to the method of Hermans and Weidinger, is 0.3. The wide‐angle x‐ray diffraction diagram shows seven reflections, not completely independent of one another. These x‐ray data do not allow an exact determination of the structure. The main chins possibly form quaternary helices (e. g., 4/1 or 7/2 helices) and the side chains are arranged in triclinic structure. The unit cell may be monoclinic: a ∼ 0.56 nm, b ∼ 3.8 nm, c ∼ 0.76 nm (in case of a 4/1 helix), β ≃ 97° The melting temperature is 278 K and the heat of fusion amounts to 30 J/g.
Chloromethylated polystyrene reaction with tris(2‐hydroxyethyl)amine. I. Crosslinked polymers prepared by chloromethylated polystyrene with tris(2‐hydroxyethyl)amine
Authors: Luca Cornelia , Drǎgan Stela , Bǎrboiu V. , Dima M. 
Published: April 2003

AbstractA multifunctional crosslinked polymer resulted from a chloromethylated polystyrene reaction with tris(2‐hydroxyethyl)amine. A benzyl chloride reaction (chosen as a structural unit model) with tris(2‐hydroxyethyl)amine was investigated to explain the reasons for the crosslinking. Amino‐ethers and tris(2‐hydroxyethyl)amine hydrochloride in addition to ammonium quaternary salt were isolated from this reaction. The formation of amino‐ethers proved that an ammonium quaternary salt rearrangement also takes place during the quaternization reaction. This rearrangement leads to chloromethylated polystyrene during its reaction with tris(2‐hydroxyethyl)amine.
Cationic polyelectrolytes. I. Soluble polymers prepared from reaction of chloromethylated polystyrene with tris(2‐hydroxythyl)amine
Authors: Drǎgan Stela , Luca Cornelia , Petrariu I. , Dima M. 
Published: April 2003

AbstractThe reaction of chloromethylated polystyrene with tris(2‐hydroxyethyl)amine in N,N‐dimethylformamide is described for the conditions to prepare soluble reaction products. The groups of the quaternary ammonium salt, which appear in the first stage of the reaction, transpose to the amino‐ether groups. The reaction was followed by elementary analysis, IR and 1H‐NMR spectra, and viscosimetric measurements for nondialyzed and dialyzed samples. The presence of the tertiary amine groups on obtained polymers was also shown by titration. The polymers from the reaction of chloromethylated polystyrene with tris(2‐hydroxyethyl)amine reacted easily with benzyl chloride.
Relation between the thermal behavior of polyacrylonitrile and polymerization factors
Authors: Minagawa Masatomo , Iwamatsu Takashi 
Published: April 2003

AbstractIn order to clarify the mechanism to produce the large dispersion of the exothermic peak temperature (Tpk) of polyacrylonitrile, a systematic and quantitative study was made by means of the differential thermal analysis and the viscosity measurment. General tendency between Tpk and the polymerization methods was reconfirmed. Under a controlled condition (i.e., aqueous solution system), presence of N,N‐dimethyl formamide or isopropyl alcohol produced a lower Tpk of resulting polymer, while presence of activator produced a higher Tpk. Thus, the large dispersion of Tpk (250–300°C) can be explained inclusively in terms of a single reaction factor, i.e., chain transfer mechanism. Particularly in the above third case it was shown that owing to strong and rapid chain transfer to activator, some kind of secondary reaction (caused by propagating chain end radical), probably chain branching which deteriorates the higher thermal quantity of molecule, is restrained effectively. Furthermore, some specific behaviors (i.e., cooperativeness and dynamic character, etc.) were observed in this reaction of PAN in solid amorphous phase.
Polymerization ofN‐carboxy‐amino acid anhydrides in the solid state. I. Polymerizability of the various α‐amino acid NCAs in the solid state
Authors: Kanazawa Hitoshi , Kawai Tohru 
Published: April 2003

AbstractThe solid‐state polymerization of various α‐amino acid NCAs was investigated and the results were compared with those obtained by heterogeneous polymerization in acetonitrile. Essential differences were found in the polymerizability of the NCAs in these two systems. In the solid state, L‐leucine NCA was the most reactive among the NCAs examined, and its reactivity was even higher than in the precipitation polymerization of acetonitrile solutions. On the other hand, glycine NCA was the most inert among the NCAs examined in the solid state. The difference between the reactivities of glycine NCA and L‐alanine NCA was interpreted in terms of their crystal structures. Several kinetic features of the solid‐state polymerization were studied on γ‐benzyl‐L‐glutamate NCA.
Reactivity of 4‐vinylpyridine in the presence of Ziegler–Natta catalysts
Authors: Carlini Carlo 
Published: April 2003

AbstractThe homopolymerization of both free and aluminum alkyls complexed 4‐vinylpyridine (4VP) in the presence of Ziegler‐Natta catalysts, based on TiCl3“ARA” and aluminum or zinc alkyls, has been performed. The copolymerization of free or complexed 4VP with chiral α‐olefins or styrene (St), using the same catalysts, has also been investigated. Spectroscopic and solubility data of the polymers obtained are consistent with the presence in the above‐mentioned catalysts of several species having different reactivity and stereochemistry. Data, based on fractionation and composition of the resulting polymeric products, are reported supporting a polymerization mechanism different from that connected with a free radical initiation.
Wholly aromatic polyamides by the direct polycondensation reaction using triphenyl phosphite in the presence of poly(4‐vinylpyridine)
Authors: Higashi Fukuji , Goto Mitsuyoshi , Nakano Yoshimasa , Kakinoki Hideo 
Published: April 2003

AbstractThe polycondensation reaction of aromatic dicarboxylic acids and diamines by using triphenyl phosphite were carried out in N‐methylpyrrolidone (NMP) in the presence of poly(4‐vinylpyridine) (P4VP). The reaction, especially of terephthalic acid (TPA), was markedly facilitated to give the absence of P4VP. The reaction promoted by P4VP was further favored by the addition of various pyridine derivatives; of the pyridines examined, pyridine was most effective, giving the best results at a high level (pyridine/P4VP values up to 26). P4VP of the molecular weight in the range of 1.3 × 104−3.0 × 105 did not affect the viscosity of the resulting polymer. These favorable additive effects of P4VP on the reaction of TPA were not observed in the reactions of isophthalic acid, and m ‐and p‐aminobenzoic acids.
Effect of simultaneous polyaddition reaction on the curing of epoxides
Authors: Bokare U. M. , Gandhi K. S. 
Published: April 2003

AbstractEpoxy‐amine curing reactions were theoretically studied using expectation theory taking into account the different reactivities of (1) the primary and secondary amine hydrogens and (2) the secondary hydroxyl group generated when an amine reacts with an epoxy group. The curing compositions and the fractional conversions at the gel point were computed. Generally the hydroxyl groups react slower than the amines and user these conditions, the reactivity of the OH group has a significant effect only when there is an intial excess of epoxide over the amine. The hydroxyl activity effectively increases the functionality of the epoxides and gelation can occur where it may not be expected.
Intramolecular excimer formation in polyamides with widely separated naphthyl groups in the backbone
Authors: Ibemesi J. A. , Kinsinger J. B. , El‐Bayoumi M. Ashraf 
Published: April 2003

AbstractThe photophysical properties of a series of polyamides containing naphthalene groups in the backbone were investigated. The polyamides were synthesized by interfacial polycondensation involving 2,6‐bis(N‐methyl, methylamino)naphthalene and the following diacid chlorides:
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(x = 2, 4, 6, and 8). The polyers were designated P‐2, P‐4, P‐6, and P‐8. The monomer model compound (MC) was made by acylation of the diamine monomer wth acetyl chloride. The polyamides exhibited intramoleular excimer fluorescence in dilute solutions at room temperature. Excimer fluorescence quantum yields were in the following order: P‐2 ≈ P‐8 > P‐4 ≈ P‐6. This sequence was rationalized on the basis of neighboring and nonneighboring group excimeric interactions that are dependent on the length of the intervening methylee chain. Temperature measurements on P‐2 revealed a small energy of actvation (1.8 kcal mole−1) for the conformational transition involved in the formaton of the intramolecular excimer. Intramolecular excimer formation for a given polymer depended on the solvent. Nanosecond fluorescence depolarization measurements demonstrated the flexibility of the naphthalene moieties even though they were doubly bound in the polymer chain. Our results showed that intramolecular excimer formation could occur over long distances of separation (n > 3) between the nteracting chromophores provided that the connecting chain was sufficiently flexible.
Functional monomers and polymers. LXIII. A study on the polymer–polymer interaction between nucleic acid base‐substituted poly‐L‐lysines
Authors: Ishikawa T. , Inaki Y. , Takemoto K. 
Published: April 2003

AbstractA study of polymer‐polymer interaction was made on several poly‐L‐lysines that contained pendant nucleic acid bases substituted on the N′ position. Conformation and interaction of these polypeptides were studied in solution by spectroscopic measurement. The results obtained suggest that the high‐molecular‐weight polymers form polymer complexes in a helical conformation by specific adenine‐thymine base pairing. On the other hand, no interaction could be observed for the low‐molecular‐weight polymers, which existed in a random coil structure.