bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the reaction of poly(α‐methylstyryl sodium, potassium, and cesium) with t‐butyl chloride in tetrahydrofuran
Authors: East G. C. , Ellis H. A. 
Published: April 2003

AbstractThe kinetics of the reaction of “living” poly(α‐methylstyrl sodium, potassium, and cesium) with t‐butyl chloride have been studied spectrophotometrically in tetrahydrofuran (THF) in the temperature range 283–303 K. The reactions, when the free ions present in solution are suppressed by tetraphenylboron salt, are first order with respect to both living ends and halide concentrations. Additions of tetraphenylboron salts produce a slight retardation effect on the rate of reaction in the case of sodium, indicating only a small contribution of free ions to the overall rate; in the case of potassium, there is no apparent effect. Analysis of the data indicates that the free ion is approximately 30 times more reactive than the sodium ion pair. The Arrhenius plots for contact ion‐pair termination are linear and the activation energies and preexponential factors determined are E = 38.6 kJ mole−1, log A = 4.44 liter mole−1 sec−1 and E = 46.0 kJ mole−1, log A = 5.10 liter mole−1 sec−1. The reaction mechanism is interpreted in terms of elimination plus some side reaction to produce two unexpected reaction products—isobutane and a 315–320‐nm absorbing grouping in the polymer.
Thermal degradation of vinyl alcohol/vinyl acetate copolymers. III. Study of the reaction products
Authors: Vasile Cornelia , Cas̨caval C. N. , Barbu P. 
Published: April 2003

AbstractThe thermal decomposition of vinyl alcohol/vinyl acetate copolymers have been studied at p = 10−2–10−4 Torr and T = 0–600°C. The decomposition products (solids, liquids, and gases) have been characterized by infrared (IR) and ultraviolet (UV) spectroscopy, gas chromatography, vapor pressure osmometry, and elemental analysis. It has been ascertained on the basis of the obtained data that the decomposition mechanism of the vinyl alcohol/vinyl acetate copolymers depends on the chemical composition and sequence distribution of comonomers.
Synthesis and thermal properties of crosslinkable phosphazene copolymers
Authors: Zeldin Martel , Jo Won Ho , Pearce Elim M. 
Published: April 2003

AbstractPolyphosphazenes of formula [NP(OC6H4CN)x(OCH2CF3)2−x] (x = 0.04–2) were prepared. The copolymers were crosslinked via cyclotrimerization of the nitrilic function, using acid catalysts (chlorosulfonic acid, aluminum chloride) at elevated temperatures. The thermal properties of the crosslinked cyclomatrix polymer were compared to the linear polymer by thermogravimetric analysis and differential scanning calorimetry. When the 4‐cyanophenoxy‐2,2,2‐trifluoroethoxy ratios were less than 0.2, the crosslinked polymers were soluble in polar organic solvents.
Etude structurale du polypentadiene‐1,3 par spectrometrie de RMN du 13C
Authors: Aubert Patrick , Sledz Joseph , Schué F. , Brevard Christian 
Published: April 2003

AbstractThe structure of stereoregular polymers of 1,3‐pentadiene was determined by 13C‐NMR spectroscopy at 22.6 MHz. Not only was it possible to distinguish between cis‐1,4 and trans‐1,4 but also between isotactic and syndiotactic cis‐1,4 structures. Triad effects were detected in the trans‐1,2 syndiotactic polypentadiene; 1,4–1,2 as well as 1,4–4,1 linkages were observed.
Determination of reactivity ratios for the copolymerization of styrene and styrene–acrylonitrile with polybutadienes
Authors: Hayes Robert A. 
Published: April 2003

AbstractThe copolymerization of styrene and styrene–acrylonitrile with polybutadienes of various microstructures was studied and the reactivity ratios determined. It was shown that for the styrene/acrylonitrile/polybutadiene systems the 1,2 structure is twice as reactive as the trans and four times as reactive as the cis. Studies in the temperature range of 50–80°C reveal that the reactivity of the polybutadiene increases as the temperature rises. When styrene is the monomer the reactivity of polybutadiene and the temperature effect is less intense than when styrene–acrylonitrile is used.
Heats of reaction of two common cellulose solvents with various model compounds
Authors: Dale Bruce E. , Tsao George T. 
Published: April 2003

AbstractHeats of reaction of two common cellulose solvents, cadoxen and ferric sodium tartrate (FeTNa), with a variety of cellulose‐related compounds were obtained with a sensitive adiabatic microcalorimeter. Both solvents require adjacent hydroxyl groups in the equatorial positions of ring systems for maximum reactivity (or maximum exothermic heat of reaction). The cellulose solvent cuprammonium has a significantly different pattern of reactivity toward a number of sugars compared with the patterns observed for cadoxen and FeTNa. These differences are explained in terms of the Jahn‐Teller effect and the preferred sites of reaction and oxidation in ring systems. Calorimetric evidence indicates that complexes containing methoxy groups may be formed by both cadoxen and FeTNa.
Oligomeric bishydroxybutyl terephthalates from terephthalic acid
Authors: Padias A. Buyle , Hall H. K. 
Published: April 2003

AbstractA process that uses terephthalic acid and excess 1,4‐butanediol for the production of polybutylene terephthalate was investigated and the reaction conditions were maximized for fast reaction and minimal loss of butanediol by dehydration to tetrahydrofuran. For best results a mixed catalyst was selected: butylstannoic acid and titanium tetrabutoxide (0.05 and 0.025 mole %, respectively, versus terephthalic acid) with a starting material ratio of butanediol: terephthalic acid of 1.7 at 210°C. The mixture cleared at 2.5 hr with a loss of 6% of butanediol. HPLC analysis showed that the clearing point corresponds to the disappearance of terephthalic acid and monohydroxybutyl terephthalate from the reaction mixture. Thus the polycondensation conditions can be applied before the clearing point with the result that the reaction is faster and tetrahydrofuran formation is minimized. Tetrahydrofuran is formed from butanediol in the reaction mixture by acid catalysis. Excess butanediol results in the formation of larger amounts. End group cyclization of terephthalate esters accounts for the slow tetrahydrofuran formation in the absence of excess butanediol.
Preparation of phosphorus‐containing polymers. XXV. Polyamide‐imides that contain phenoxaphosphine rings
Authors: Sato Moriyuki , Tada Yuji , Yokoyama Masaaki 
Published: April 2003

AbstractNew phenoxaphosphine‐containing polyamide‐imides were prepared by cyclodehydration of the polyamide‐amic acids obtained from 8‐chloroformyl‐10‐phenylphenoxaphosphine‐2,3‐dicarboxylic anhydride 10‐oxide and diamines by a low‐temperature solution polycondensation. Polymers with reduced viscosities of 0.10–0.59 dl/g in DMA or concentrated H2SO4 at 30°C were obtained in 64–97% yields. All the polyamide‐imides were soluble in m‐cresol, concentrated H2SO4, and dichloroacetic acid and some of them were soluble in DMF, DMA, and DMSO; the polyamide‐imides had better solubility in organic solvents than phenoxaphosphine‐containing polyimides. The phenoxaphosphine‐containing polyamide‐imides derived from aromatic diamines exhibited excellent thermal properties and little degradation below about 400°C, whereas the polymers from aliphatic diamines began to lose weight at about 250°C. They appeared to have thermal stability between phenoxaphosphine‐containing polyimides and polyamides. These polyamide‐imides exhibited self‐extinguishing behavior.
Syntheses and reduction of polymers with alloxan structures
Authors: Endo Takeshi , Fujiwara Eishuke , Okawara Makoto 
Published: April 2003

AbstractThe polymer(Poly A) which contains alloxan moiety was prepared by the oxidation of the copolymer of allyl barbituric acid and vinyl acetate with chromium trioxide. The photoreduction of Poly A by ultraviolet (UV) irradiation was used to isolate the polymer(Poly A·) in which the alloxan radical was present. The properties of this polymer(Poly A·) thus obtained were investigated. Poly A was also reduced by chemical agents to obtain the polymer(Poly D) which had a dialuric acid structure.
Radical copolymerization of proto‐hemin dimethyl ester
Authors: Nishide Hiroyuki , Shinohara Kenichi , Tsuchida Eishun 
Published: April 2003

AbstractIron(III) proto‐porphyrin IX dimethyl ester (HDME) can copolymerize with π‐conjugated monomers binding at one end of the polymer chain. Apparent Q, e values of HDME were Q = 70 and e = −0.17. The copolymerization of HDME with π‐unconjugated monomer was feasible by using π‐conjugated monomer as a third component. When unconjugated vinylimidazoles were used as monomers, the obtained ternary copolymers of HDME formed intramacromolecular complexes of iron(II) porphyrin with vinylimidazole residues, which gave stable carbon monoxide adducts.
Analysis of the linear methods for determining copolymerization reactivity ratios. VI. A comprehensive critical reexamination of oxonium ion copolymerizations
Authors: Tüdos F. , Kelen T. , Turcsányi B. , Kennedy Joseph P. 
Published: April 2003

AbstractThe reactivity ratios of 180 published oxonium copolymerization systems have been reviewed in terms of the extended Kelen–Tüdos method. Only 32 (17.8%) systems were described in sufficient detail for reevaluation and classification. r Values, together with their 95% confidence limits have been calculated. A quantity δ□, suitable for classification of the systems, has been introduced. Of the 32 reevaluated systems, five were found to belong to class I and 14 to class I(!), i.e., 19 systems for which the conventional copolymerization equation was found to be adequate. Class II systems were not found. Finally, 13 systems were judged to belong in class III, i.e., systems for which the experimental data are inconsistent and the published r values meaningless.
ESR of free radical reactions in gamma‐irradiated ethylene–propylene‐based terpolymers. II
Authors: Faucitano A. , Buttafava A. , Cesca S. 
Published: April 2003

AbstractThe gamma irradiation at liquid nitrogen temperature of dicyclopentadiene, 2‐methylennorbornene, and cyclopentadienyl‐5‐endo‐norbor‐2‐enyl‐methane‐based ethylene–propylene terpolymers leads to the formation of macroradicals of the alkyl type by loss of hydrogen atoms from the ethylene–propylene chains. When warmed almost to glass transition temperature these primary alkyl species decay and generate new radicals by the double‐bond addition and/or H abstraction from the unsaturations. The nature of the radical products was determined by ESR and MO methods.
Preparation and properties of aromatic polypyrazoles from branched bis‐β‐diketones and aromatic dihydrazines
Authors: Imai Yoshio , Nakajima Toshio , Ueda Mitsuru 
Published: April 2003

AbstractAromatic polypyrazoles were prepared by the cyclopolycondensation of branched bis‐β‐diketones with aromatic dihydrazines. The polymerizations were carried out at 100–150°C in m‐cresol or a polar aprotic solvent like dimethyl sulfoxide to produce polymers with inherent viscosities up to 0.98 dl/g. These polypyrazoles were readily soluble in a wide range of solvents that included chloroform and exhibited 10% weight losses between 380 and 425°C in air and 370 and 500°C in nitrogen.
Radiation‐induced polymerization at high dose rate. V. Butadiene in bulk
Authors: Hayashi Kanae , Tanaka Yoshinori , Okamura Seizo 
Published: April 2003

AbstractBulk butadiene was polymerized by a cationic mechanism in a wide dose rate range. The M̄n of the product was about 2300, independent of dose rate. The polymer had 83% residual unsaturation and the remaining double bond was 77% trans and 23% vinyl and had no cis unit. When the polymer yield exceeded 10% gel was formed, but the value of the residual unsaturation in the polymer remained unchanged. This indicated a mechanism that correlated propagation, cyclization, and crosslinking reactions with a cationic intermediate.
Compatibility studies of styrene and hydroxyl containing styrene copolymers with poly(ethylene oxide)
Authors: Ting S. P. , Bulkin B. J. , Pearce E. M. , Kwei T. K. 
Published: April 2003

AbstractCopolymers of styrene with vinylphenyl trifluoromethyl carbinol, p‐vinylphenyl trifluoromethyl carbinol, vinylphenyl hexafluorodimethyl carbinol, and p‐vinylphenol are conditionally compatible with poly(ethylene oxide), depending on their composition and blending ratios, whereas copolymers of styrene and vinylphenyl methyl carbinol are much less compatible with poly(ethylene oxide), as determined by Tg criteria and differential scanning calorimetry. The crystallinity of poly(ethylene oxide) is changed in the copolymer/poly(ethylene oxide) blends, as indicated by depressions of the poly(ethylene oxide) melting point. Hydrogen‐bond formation has been studied in two selected blends by infrared (IR) spectroscopy. Hydrogen bonding dissociation and reassociation as a function of temperature are reported. The conformation changes of poly(ethylene oxide) in the blends, the interaction between copolymer and poly(ethylene oxide) as well as in the reference blend, polystyrene/poly(ethylene oxide), are also investigated.
Radical processes in polymer burning and its retardation. I. ESR methods for studying the thermal decomposition of polymers in the preflame and flame zones
Authors: Tkáč A. 
Published: April 2003

AbstractThe determination of the free radical distribution in the preflame and flame zones of a burning polymer (polypropylene) by ESR leads to the conclusion that in all phases of the burning polymer an exothermic reaction zone encloses an oxygen‐free pyrolytic zone. Whereas in the molten preflame zone (250–350°C) the polymer decomposes to oligomers, dimers, monomers, and the relevant free radicals or biradicals, in the gaseous flame zone the heat transport from the hot outer surface into the surrounding pyrolytic zone leads (with an increasing temperature gradient) to a progressive formation of thermodynamically more stable decomposition products. The CH. radicals generated at 400–800°C, after rapid cooling, yield polyaromaties with delocalized free electrons and the atomized carbon and its dimers at 800–1200°C, after cooling, yield graphite sheets with localized free electrons in its defects. Free radicals and paramagnetic species are trapped (a) in the gaseous pyrolytic products of heated polymers on the surface of a rotating cryostat, (b) in burning polymer drops by quenching in liquid nitrogen, and (c) in different zones of a burning diffuse flame. The superimposed ESR signals of the paramagnetic products are then qualitatively and quantitatively analyzed.
Grafting of monodisperse low‐molecular‐weight polystyrene onto cellulose acetate
Authors: Månsson Per , Westfelt Lars 
Published: April 2003

AbstractWell‐defined low‐molecular‐weight polystyrene was grafted onto cellulose acetate in a homogeneous solution. The grafting was performed by esterifying the free hydroxyls in the cellulose acetate (acetyl DS 2.5) with anionically prepared polystyrene having a carboxylic acid group at one end of the chain. The carboxylic acid end group of the polystyrene was activated by either conversion to the corresponding acid chloride, or by reaction with trifluoroacetic anhydride. Pyridine and the more active 4‐dimethylaminopyridine were used as catalysts in the esterifications. The polystyrene contents of the copolymers varied between 10 and 80% and the molecular weights of the polystyrene grafts were 2500, 12,100 and 17,100 (M̄w/M̄n = 1.1).
Radiation‐induced copolymerizations of perfluorovinyl acetic acid and its methyl ester with α‐olefin
Authors: Kawaguchi Mitsuo , Watanabe Terutaka , Matsuda Osamu , Tabata Yoneho , Machi Sueo 
Published: April 2003

AbstractHomopolymerizations and copolymerizations of perfluorovinyl acetic acid (FVA) and its methyl ester (MFVA) were carried out by γ radiation at a temperature of 25°C, a dose rate of 1 × 106 rad/hr, and FVA/α‐olefin and MFVA/α‐olefin ratios of 10/90‐90/10 in the monomer mixture. FVA and MFVA gave small quantities of brown and greasy low‐molecular‐weight homopolymers. The polymerization rates of both FVA and MFVA were extremely small, as shown by the maximum G value of monomer consumption of 12. FVA and MFVA reacted with α‐olefin to form waxlike copolymers. The copolymerization rates of both FVA and MFVA with α‐olefin were remarkably larger than those of the homopolymerizations, particularly with ethylene. The polymer compositions of FVA/ethylene or MFVA/ethylene was nearly 1/2 over a wide range of the monomer compositions. The Mayo–Lewis method gave negative r1 (FVA) and r1 (MFVA). The polymer composition curves could be well interpreted by introducing the penultimate model.
Fundamental considerations on the mechanism of copolymerization of trioxane and ethylene oxide initiated with boron trifluoride dibutyl etherate
Authors: Collins G. L. , Greene R. K. , Berardinelli F. M. , Ray W. H. 
Published: April 2003

AbstractA comprehensive mechanistic scheme that accounts for the unique experimental features of the copolymerization of bulk trioxane (TOX) with 2% (wt/wt) ethylene oxide (EO) was developed. The formation of the primary initiating species is shown as the diffusion‐limited reaction of trace water with boron triflouride dibutyletherate [BF3O(Bu)2] to form a Bronsted acid. This acid complexes principally with the more basic EO and partly with the less basic TOX. The acid‐complexed TOX depolymerizes to formaldehyde which can react with acid‐complexed EO in an insertion reaction to form an acid‐complexed dioxolane. Further insertion of formaldehyde yields an acid‐complexed trioxepane. This sequence is generalized into a propagation scheme that involves propagation by expansion and ring opening. Displacement of complexed dioxolane and trioxepane can occur in the event that the more basic EO attacks the oxonium‐active site at the reactive position outside the oxonium ring. These displacement reactions account for the observation of formation of dioxolane and trioxepane. The polymerization of formaldehyde is not considered significant until all EO has been consumed. During the latter stages of polymerization, cyclic oxonium‐active sites are transformed into oxocarbenium sites that are stabilized by complexation with the polymer chain. This complexation is the origin of the phenomena of transacetalization and hydride transfer.
Studies of the formation of thermosetting resins. XII. Computer simulation of the reactions of phenols with formaldehyde
Authors: Ishida Shin‐Ichiro , Tsutsumi Yoshitomo , Kaneko Katsumasa 
Published: April 2003

AbstractThe mechanism of the reaction of phenols with formaldehyde was studied by computer simulation. At first starting molecules were stored in a computer and the hypothetical reaction yielded conditions like the reactivity ratio of hydroxymethyl group to formaldehyde and that of orthohydrogen to parahydrogen. The molecular weight distribution of the hypothetical product in the computer was compared with that of the prepared resin determined from GPC measurement. Reaction mechanisms were discussed. We also confirmed, by computer simulation, that the rate of methylenation is larger than that of hydroxymethylation in an acid‐catalyzed system and that the reactivity ratio of hydroxymethyl group to formaldehyde is 5–12 for the reaction of phenols such as o‐cresol, p‐cresol, and phenol with formaldehyde. The opposite results were obtained in a base‐catalyzed system. It also became apparent that information regarding molecular structures, such as the number of branches, the number of phenolic nuclei in the longest chain, and the number of o,o′‐,o,p′‐ and p,p′‐methylene linkages, can be obtained by computer simulation. The most probable values of these factors for 10 mer of a phenol–formaldehyde condensation molecule are 2, 7, 2, 5, and 2.
Polyethylenimine catalysts containing an isolated apolar binding site: Solovolysis of p‐nitrophenyl esters
Authors: Pavlisko J. A. , Overberger C. G. 
Published: April 2003

AbstractThe preparation dodecane‐block‐poly[ethylenimine‐graft‐4(5)‐methylimidazole] copolymers and related model compounds has been described and such polymers have been described and such polymers have been demonstrated to be efficient catalysts for the hydrolysis of activated phenyl esters in aqueous solutions. Polymeric catalysts that contain isolated apolar blocks exhibited enhanced catalytic activity for the hydrolysis of the p‐nitrophenyl esters of acetate and butyrate compared with polymer model compounds. This rate enhancement was atributed to the apolar binding of substrate within the apolar polymer regime. Twenty‐to 100‐fold increases in the second‐order rate constants were observed for the hydrolysis of the longer‐chain p‐nitrophenyl esters. This is indicative of a significant hydrophobic interaction. The contribution of the apolar block to the hydrophobic interaction was masked in the hydrolysis of the p‐nitrophenyl caproate and p‐nitrophenyl laurate substrates. In both instances the dominant contribution to the hydrophobic interactions was ascribed to a substrate‐imidazole intermediate rather than the apolar block of the catalyst. The pH‐rate profiles for the hydrolysis of p‐nitrophenyl esters by the various catalysts indicated an absence of any cooperative interactions between imidazole residues or amine groups.
Cationic metal nitrosyl complexes. IV. Polymerization of olefins with dinitrosyl iron complexes
Authors: Ballivet‐Tkatchenko D. , Billard C. , Revillon A. 
Published: April 2003

AbstractThe polymerization of styrene was performed with new cationic iron complexes, (Fe(N‐O)2Sn)+PF6−(BF4−, CIO4−), where Sn represents solvent molecules such as CH2Cl2, THF, and MeCN. Kinetic experiments showed a first‐order dependence of (Rp)0 on the monomer and iron complex concentrations. The molecular weight determinations suggested that the termination process is fast and occurs by chain transfer to monomer. An extension of this polymerization to α‐methylstyrene, isobutene, tetrahydrofuran, and styrene‐methylmethacrylmate system emphasized the cationic nature of the reaction.
Functional monomers and polymers. XCIII. Photochemical reactions on the acrylic and methacrylic copolymers containing thymine bases
Authors: Kita Yasuo , Uno Taizo , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractPhotodimerization of Polyacrylic and polymethacrylic derivatives with different pendant thymine unit content was studied in dimethylformamide solution. The quantum efficiency of thymine base for the photodimerization increased with increasing thymine content in the copolymers. The quenching study, which used isoprene as the quencher, revealed that the photodimerization resulted from excited singlet state increases with increasing thymine content. The photochemical results were discussed in terms of self‐association of thymine bases in the polymer chain.
Complexation of metal ion with poly(1‐vinylimidazole) resin prepared by radiation‐induced polymerization with template metal ion
Authors: Kato Masayuki , Nishide Hiroyuki , Tsuchida Eishun , Sasaki Takashi 
Published: April 2003

AbstractPoly(1‐vinylimidazole) (PVI) resin was prepared with Ni2+, Co2+, or Zn2+ as a template to study the adsorption of metal ions. The metal‐1‐vinylimidazole complex was copolymerized and crosslinked with 1‐vinyl‐2‐pyrrolidone by γ‐ray irradiation and the template metal ion was removed by treating the polymer complex with an acid. These PVI resins adsorbed metal ions more effectively than the PVI resin prepared without the template. The number of adsorption sites (As) and the stability constant (K) of Ni2+ complex were larger for the PVI resin prepared with the Ni ion template, caused by the smaller dissociation rate constant of Ni ion from the resin. The composition of the Ni2+ complex in the resin remained constant. This suggests that the complexation proceeded via a one‐step mechanism.