bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical processes in polymer burning and its retardation. II. An ESR study of flame retardation of polypropylene
Authors: Tkáč A. , Špilda I. 
Published: April 2003

AbstractQualitative and quantitative free radical transformations between polypropylene alkyl radicals, oxygen, and brominated flame retardants in the molten and gaseous phases of thermally treated samples are described. By ESR technique it has been proved that, depending on the applied pressure during pyrolysis, highly reactive peroxy radicals or less reactive radicals of the retardant are formed. For flame‐retarded samples, compared with polypropylene without additives, the concentration of the primary alkyl radicals transferred from the molten to the gaseous phase is reduced by two orders of magnitude (from 7 × 1014 to 7 × 1012 spins/0.02 g), whereas the limiting oxygen index [LOI] is raised from 17–18% to 25–26%. The great variety of physical and chemical processes proceeding in molten polymer in the preflame zone and burning gaseous phase calls for use of different retardant types with a programmed release of Br and HBr with the temperature increase. The chain oxidation of the “fuel,” a product of the endothermic decomposition of polymer, determines the temperature of self‐ignition according to the number of initiating alkyl and allyl radicals formed per unit time; the [LOI] index depends more on the length of the kinetic chain of propagation reactions in the stationary process of oxidation at a given pressure.
Cationic copolymerization of β‐pinene and epichlorohydrin
Authors: Martínez F. , Gajardo I. 
Published: April 2003

Abstractβ‐Pinene and epichlorohydrin (ECH) have been copolymerized cationically using BF3(C2H5)2O and SnCl4 as catalysts. Polymerizations were carried out at −80°C in methylenechloride. Monomer reactivity ratios were determined in both catalysts which were r1(ECH) = 1.06 ± 0.15 and r2 (β‐pinene) = 0.32 ± 0.08 in BF3(C2H5)2O and r1(ECH) = 0.33 ± 0.11 and r2(β‐pinene) = 2.03 ± 0.44 in SnCl4. Copolymers of different composition were soluble in acetone and insoluble in methanol. This characteristic was taken to indicate that the polymeric products were real copolymers and not a mixture of two homopolymers of epichlorohydrin and β‐pinene.
Production of a poly(pyridinyl radical) by reduction with 1‐benzyl‐1,4‐dihydronicotinamide and N,N′‐dicyclohexylalloxan
Authors: Endo Takeshi , Okawara Makoto 
Published: April 2003

AbstractIt was found that 1‐ethyl‐4‐carbomethoxypyridinium iodide could be reduced by 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) and N,N′‐dicyclohexylalloxan (DCA) to give 1‐ethyl‐4‐carbomethoxypyridinyl radical. The stable poly(pyridinyl radical) (P‐III) was obtained in a similar manner by the reduction of poly(pyridinyl salt) (P‐II).
Emulsion polymerization and copolymerization of vinyl benzoate
Authors: Plavljanić B. , Janović Z. 
Published: April 2003

AbstractEmulsion polymerization of vinyl benzoate and its copolymerization with vinyl acetate or styrene are described. The effect of the potassium persulfate initiator, and the sodium lauryl sulfate emulsifier concentration on the rate of vinyl benzote homopolymerization and the molecular weight of the polymers was determined. In copolymerization with vinyl benzoate, both comonomers, vinyl acetate and styrene, decrease the initial polymerization rate. With increasing amounts of styrene in the comonomer mixture the polymerization rate increases but with vinyl acetate an opposite effect is observed. Reactivity ratios of copolymerizations were determined. For the vinyl benzoate [M1]‐styrene [M2] comonomer system a r1 = 0.03 and a r2 = 29.58 and for vinyl benzoate [M1]‐vinyl acetate [M2], a r1 = 1.93 and a r2 = 0.20 was obtained. From the vinyl benzoate‐styrene reactivity ratios the Qe parameters were calculated.
Sequence distributions of vinyl chloride‐vinyl acetate and vinyl chloride‐vinyl propionate copolymers
Authors: Okada Tadashi , Hashimoto Kazue , Ikushige Tetsuo 
Published: April 2003

Abstract13C‐NMR spectroscopy was used in a detailed study of vinyl chloride‐vinyl acetate and vinyl chloride‐vinyl propionate copolymers. The NMR spectra of the methylene carbon region showed three split peaks whose intensities changed with composition of the copolymers. These peaks were assigned to diad sequences and the observed diad concentrations were in good agreement with the calculated concentrations in terms of the random copolymerization theory. For the methine carbon spectra of vinyl acetate or vinyl propionate units in the copolymers the degree of splitting of the signal was improved by the addition of tris(1,1,1,2,2,3,3‐heptafluro‐7,7‐diemthyl‐1,4,6‐octanedinata)‐praseodymium as a shift reagent. Four peaks assigned to the methine carbon were interpreted in terms of triad sequence distribution and tacticity.
Cationic oligomerization of anethole: Selective synthesis of dimers and trimers
Authors: Higashimura Toshinobu , Hiza Misao 
Published: April 2003

AbstractA linear unsaturated dimer of anethole [II, (E)‐1,3‐bis(p‐methoxyphenyl)‐2‐methylpentene‐1], was prepared in 98% yield with an acetyl perchlorate (AcClO4) catalyst in a nonpolar solvent (C6H6) at a high temperature (70°C). At 0°C a linear unsaturated trimer was formed in high yield with dimer II. The geometric structure of the linear unsaturated dimers was determined by analysis of the nuclear Overhauser effect (NOE) on their 1H‐NMR spectra. NOE analysis showed that at 0°C with AcClO4, trans‐anethole gives the (E)‐form (II), whereas cis‐anethole yields the (Z)‐form. On the other hand, with a metal‐halide catalyst (BF3OEt2) a cyclic dimer and a cyclic trimer were produced in high yields in a polar solvent [(CH2Cl2)] at 70°C; higher oligomers (≥ tetramer) were scarcely formed. The effect of catalysts on the structure of oligomers was explained in terms of the interaction between a growing carbocation and a counterion.
Preparation of polystyrene with long chain branches via free radical polymerization
Authors: Tung L. H. , Hu A. T. , McKinley S. V. , Paul A. M. 
Published: April 2003

AbstractPolystyrene with random long chain branches has been difficult to prepare. A new approach using small amounts of chain‐transferring monomers to copolymerize with styrene free radically was examined in this work. Of the several comonomers examined, vinylbenzylthiol yielded polystyrene with branched structure. But because of the high chain trnsfer constant, the branches occurred mainly in the low‐molecular‐weight end of the distribution. As a side interest, vinylbenzylthiol was found to be an effective agent for the broadening of molecular weight distribution.
Polymers with improved flammability characteristics. II. Phenolphthalein related copolycarbonates
Authors: Lin M. S. , Pearce E. M. 
Published: April 2003

AbstractAnalysis of phenolphthalein and bisphenol‐A copolycarbonates reveals a linear correlation between oxygen index (OI) and char yield (Y): OI = 0.34Y + 19.6, which can be compared with the empirical equation QI = 0.4Y + 17.5 proposed by D. W. Van Krevelen for other polymers. Analysis also suggests that no chemical interction occurs between the two comonomers during pyrolysis, which leads neither to enhanced char yield nor to enhanced oxygen index. Each copolymer component contributes to the char yield and oxygen index on an additive basis. Study of 4,5,6,7‐tetrabromophenolphthalein and phenolphthalein copolycarbonates shows that some enhancement of char yield does occur and that the lower the char yield, the higher the oxygen index, which is an indication of the predominance of a vapor‐phase bromine effect over that related to char. Study of 4,5,6,7‐tetrabromophenolphthalein and bis‐phenol‐A copolycarbonates is interpreted on the basis of two factors—the char effect that prevails over the vapor phase radical scavenging effect at lower bromine content and the reverse order at higher bromine content.
Preparation and properties of aromatic polypyrazoles from linear bis‐β‐diketones and aromatic dihydrazines
Authors: Imai Yoshio , Nakajima Toshio , Ueda Mitsuru 
Published: April 2003

AbstractThe cyclopolycondensation of linear bis‐β‐diketones with aromatic dihydrazines in dimethyl sulfoxide at 100–150°C produced a series of aromatic polypyrazoles with inherent viscosities up to 0.6 dL/g. All the polymers were highly soluble in a wide range of solvents, which included tetrahydrofuran and chloroform. The polypyrazoles showed excellent thermal stability with 10% weight loss at 410–490°C in air and nitrogen atmosphere.
Linear polythioesters. V. Products of interfacial polycondensation of 4,4′‐di(mercaptomethyl)‐benzophenone with some aliphatic acid dichlorides
Authors: Podkoscielny Wawrzyniec , Kultys Anna 
Published: April 2003

AbstractNew polythioesters by interfacial polycondensation of 4,4′‐di(mercaptomethyl) benzophenone with oxalyl, succinyl, adipoyl, suberoyl, and sebacoyl chlorides were obtained. To determine the optimal conditions for interfacial polycondensation the influence of the following factors on yield and value of reduced viscosity were studied: type of organic phase, the quantitative ratio of aqueous and organic phase, concentration of hydrogen chloride acceptor, molar ratio of reagents, temperature of reaction, rate of acid chloride addition, and contribution of catalyst and emulsifier. A thorough examination was carried out only for polycondensation of dithiol with adipoly and sebacoyl chlorides. The structure of all polythioesters obtained under the model conditions was determined by elementary analysis and infrared spectra. Initial decomposition and initial intensive decomposition temperature were defined from the curves of thermogravimetric analysis. Some mechanical and electrical properties of the polythioesters obtained from 4,4′‐di(mercaptomethyl)benzophenone and adipoyl and sebacoyl chlorides were determined. The molecular weight was not measured because of the low solubility of the obtained polythioesters.
15N‐NMR spectroscopy 32. Synthesis and characterization of polyelectrolytes based on polyaminamides
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractThe titrations of the polyammamides prepared from adipic acid and diethylenetriamine or di(3‐aminopropyl)methylamine were monitored by means of natural‐abundance 15N‐(NMR) nuclear magnetic resonance spectra. Opposite shift effects were found for amine and amide nitrogens upon protonation of the amino groups. These shift effects allow one to distinguish substitutions involving exchange of electric charges from other substitutions without isolation of the polymers. Reactions of the polyaminamides with β‐propiolactone, γ‐butyroslution, methyl‐methane sulfonate, prolyleneoxide, epichlorohydrine, maleic acid anhydride, succinic acid anhydride, carbon dioxide, ethylchloroformate, and methyne sulfonylchloride were carried out in water, and the resulting polyelectrolytes were characterized by means of 15N‐NMR spectra.
Formation and thermal‐induced decay of radical ions in polymer matrices
Authors: Torikai Ayako , Mishina Hitoshi 
Published: April 2003

AbstractThe formation of radical ions in γ‐irradiated polymethyl‐methacrylate (PMMA) matrices at 77°K and thermal‐induced reaction of these radical ions were of studied by optical absorption spectroscopic measurements. The radical ions of stilbene and pyrene were investigated. These radical ions decay according to second‐order kinetics, which means that the neutralization reaction of the cationic species and anionic species participates in the decay process. The kinetic plots consist of two straight lines; that is, fast and slow decay processes are concerned. The activation energies were estimated to be Efast = 2.4 kcal/mol and Eslow = 6.4 kcal/mol, respectively. The probability of recombination reaction depends on the distance between cationic and anionic species.
Spectral and thermodynamic studies of the interaction of binding site probes with poly(vinylpyrrolidone)
Authors: Reeves Richard L. , Harkaway Shelley A. , Sochor Alena R. 
Published: April 2003

AbstractThe binding of two ionic azo dyes (4‐phenylazo‐1‐naphthol mono‐and disulfonate) and a fluorescent probe (2‐p‐toluidinonaphthalene‐6‐sulfonic acid, TNS) to poly(vinylpyrrolidone) (PVP) was studied to obtain information on the nature of the interaction, binding isotherm, and binding site. Sorption of the dyes followed a Langmuir isotherm only at low polymer saturation. Apparent cooperativity in binding was seen at higher saturation. The polymer had a higher intrinsic binding constant but lower binding capacity for the doubly charged dye than for the structurally similar singly charged dye. Both dyes consisted of tautomeric mixtures of hydrazone and azonaphthol forms in equilibrium in the bound and unbound state. The preferential binding of the azonaphthol tautomer of the disulfonate was highly exothermic and accompanied by an entropy decrease. The binding of the hydrazone form was less favored by 1.8 kcal/mol, was weakly exothermic, and accompained by an entropy increase. Increased preference for the azonaphthol tautomer accompanied chain extension from charging the polymer. Chain extension had no effect on the emission frequency of bound TNS. Large differences in binding capacities for similarly charged dyes indicated the existence of specific dye‐site interactions. Arguments are presented against nonspecific hydrophobic interactions as predominant forces responsible for binding.
Photopolymerization initiated by charge‐transfer complex. I. Photopolymerization of methylmethacrylate with the use of quinaldine‐bromine and lutidine–bromine charge‐transfer complexes as photoinitiator
Authors: Mishra Munmaya K. , Lenka Subasini , Nayak Padma L. 
Published: April 2003

AbstractPhotopolymerization of MMA was carried out with quinaldine–bromine (QN–Br2) and lutidine–bromine (LU–Br2) charge‐transfer complexes as initiators. The rate of polymerization Rp increased with rising monomer concentration and the monomer exponent was computed as unity. At first the rate of polymerization accelerated and then reduced as the initiator concentration was increased. The initiator exponent was 0.5. The reaction was carried out at three different temperatures and overall activation energy was calculated at 4.0 kcal/mol. The kinetic data and other evidence indicate that the overall polymerization takes place in a radical mechanism. A suitable mechanism is suggested.
Thermomechanical trnasitions in polyphosphazenes
Authors: Choy I. C. , Magill J. H. 
Published: April 2003

AbstractUnoriented and oriented samples of two phosphazene homopolymers with chemical structure [NPX2]n, where X = CF3CH2O and p‐CH3C6H4O, and three unfilled and filled alkoxy‐type polyphosphazene copolymers, plus one filled aryloxy‐type copolymer were examined with a Rheovibron viscoelastometer. Measurements were made from −120°C to temperatures above the T(1) transition of the respective polymers. The effects of orientation and repeated temperature cycling through the T(1) transition temperatures were studied. The overall physical behavior of these polyphosphazenes was dominated by changes that occurred in the primary softening dispersion and the mesomorphic or T(1) transition region. The enthalpy of the T(1) transition and the T(1) temperature were investigated by differential scanning calorimetry (DSC) as a function of temperature cycling in the T(1) region; for instance, the change in enthalpy in the T(1) region is about an order of magnitude larger than it is at Tm for the unfilled polyphosphazene homopolymers. The Tg's of the polyphosophazenes were also determined. Density measurements were made on oriented and unoriented specimens by the flotation method. Although an increase in density (and crystallinity) was observed when specimens were cycled through the T(1) transition, no significant difference in density was found between oriented and unoriented materials. Some discussion of the molecular origin of the T(1) transition is included.
Polymerization of cyclohexene oxide with Al(acac)3‐silanol catalyst supported by zeolite and porous silica
Authors: Hayase S. , Ito T. , Suzuki S. , Wada M. 
Published: April 2003

AbstractThe polymerization of cyclohexene oxide with Al(acac)3‐silanol catalyst supported by zeolite and porous silica has been investigated. Cyclohexene oxide was also polymerized to a lesser extent by a zeolite‐silanol catalyst and an Al(acac)3‐silica gel catalyst. The catalytic activity of the zeolite‐silanol system varied with the zeolite pore size. The catalytic activity of the Al(acac)3‐silanol system was enhanced by supporting the catalyst with porous silica or zeolite. The Al(acac)3‐silanol catalyst supported by zeolite was especially effective in increasing polymer conversion and molecular weight. Catalytic activity increased with increasing chemical interaction between silanol and porous silica. The molecular weight of the polymers with these catalysts increased in the order zeolite‐silanol> zeolite‐Al(acac)3‐silanol >Al(acac)3‐silanol ≈ Al(acac)3‐silanol supported by porous silica>Al(acac)3‐silica gel.
Thermal degradation of poly[(tetramethyl‐p‐silphenylene) siloxane]
Authors: Ikeda Masao , Nakamura Takashi , Nagase Yu , Ikeda Koji , Sekine Yoshiro 
Published: April 2003

AbstractFor the purpose of studying the mechanism of thermal degradation of poly[(tetramethyl‐p‐silphenylene) Siloxane] (poly TMPS) a series of polymers with silphenylene and siloxane bonds in the main chain were prepared and subjected to thermogravimetry (TG) and pyrolysis study. Analyses of products from poly TMPS degradation (in vacuum at a constant temperature) by gas chromatography (GC), infrared (IR), nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography‐mass spectrometry (GC–MS) revealed that degradation occurs at the silphenylene bonds. The TG curves obtained in He for heating rates of 1,2,2.5,7.5, and 10°C/min were analyzed by the Ozawa method; activation energies of 39 ± 1 and 45 ± 2 kcal/mol were obtained respectively for the initial cleavage of the methyl side group and the later‐stage scission of the main‐chain silphenylene bond which leads to a major weight loss. The results agree with those obtained for other structurally similar polymers.
Dye‐sensitized photopolymerization. I. Photopolymerization of ethyl acrylate by sodium fluorescein‐ascorbic acid system in aqueous solution
Authors: Lenka Subasini , Nayak Padma L. , Mishra Munmaya K. 
Published: April 2003

AbstractThe kinetics of the polymerization of ethyl acrylate (EA) sensitized by dye‐reducing agent systems were investigated. The redox system sodium fluorescein‐ascorbic acid was used for the polymerization. The systems were buffered with phosphate buffer, and the effects of monomer, dye, temperature, etc., on the reaction system were investigated. The polymerization was followed by measurement of monomer disappearance (gravimetrically) and the chain length of the polymer formed (viscometrically). In the light of the experimental results a suitable kinetic scheme was proposed and the composite rate constants were evaluated.
Cationic polymerization by aromatic initiating systems. IV. Synthesis and characterization of α‐ω‐diphenylpolyisobutylene
Authors: Kennedy Joseph P. , Chung David Y. L. 
Published: April 2003

AbstractThe polymerization of isobutylene using ø3Al coinitiator and the tertiary chlorides tert.‐butyl chloride (t‐BuCl) and 2,6‐dichloro‐2,6‐dimethylheptane (Clt‐R‐Clt) initiators has been studied. Polymerization rates with the t‐BuCl/ø3Al and Clt‐R‐Clt/ø3Al initiating systems were high in the −20 to −70°C range. Yields and molecular weights increased with decreasing temperature. As predicted by model experiments the extent of phenylation increases with decreasing temperatures. According to spectroscopic evidence the polyisobutylenes carry phenyl end groups.
Cationic polymerizations by aromatic initiating systems. V. Oxidation and chlorination of α,ω‐diphenylpolyisobutylene and subsequent reaction with living polystyrene anions to form block copolymers
Authors: Kennedy Joseph P. , Chung David Y. L. , Guyot Alain 
Published: April 2003

Abstractα,ω‐Diphenylpolyisobutylenes produced by the Clt‐R‐Clt/ø3Al initiating system have been derivatized. Model chloromethylation of t‐butylbenzene by CH3OCH2Cl in chloroform indicated that beyond ca. 35% yield significant alkylative side reactions occurred. Phenyl end groups (average 1.5 per chain) and unsaturated chain ends (from proton elimination) have been converted to carboxyl end groups by oxidation with RuO4 in chloroform. Subsequently the carboxyl end groups were converted to acyl chloride termini by reaction with SOCl2. The latter end groups were coupled with living polystyryl anions to form isobutylene‐styrene blcok copolymers.
Synthesis of polyphthalimidines with benzylidene group from aminophthalide monomers
Authors: Imai Yoshio , Takahashi Takeyoshi , Ueda Mitsuru 
Published: April 2003

AbstractTwo aminophthalide monomers, 6‐amino‐3‐benzylidenephthalide (I) and 3‐(p‐aminobenzylidene)phthalide (II), underwent self‐polycondensation in o‐phenylphenol at 250°C to yield polyphthalimidines with inherent viscosities up to 0.5 dL/g. These polymers were readily soluble in a variety of solvents such as dimethylformamide, dimethyl sulfoxide, m‐cresol, pyridine, and methylene chloride. The temperatures at which a 10% weight loss occurred by thermogravimetry in nitrogen were 460°C for the polymer derived from I and 490°C for the polymer from II. The glass transition temperature of the polymer from I was 332°C, determined by thermomechanical analysis.
Poly[trans‐1‐(3‐vinyl‐9‐carbazolyl)‐2‐(9‐carbazolyl)cyclobutane]. Synthesis and comparison with poly(9‐ethyl‐3‐vinylcarbazole)
Authors: Inoue Takashi , Tazuke Shigeo 
Published: April 2003

AbstractTrans‐1‐(3‐vinyl‐9‐carbazolyl)‐2‐(9‐carbazolyl)cyclobutane(I) was synthesized. Homopolymerization of I and copolymerization with 9‐ethyl‐3‐vinylcarbazole(II) were conducted cationically. It was found that I polymerized to high molecular weight polymers (< 105) with good yields, although its polymerizability was lower than that of II. Copolymer composition was determined by gel permeation chromatology (GPC) analysis, based on the remaining monomer ratio. Fluorescence spectroscopy indicated that poly(I) did not form excimer. Excimer emission gradually appeared with increasing II content in poly(I‐co‐II) to the homopolymer of II. This difference between poly(I) and poly(II) was attributed to the crowded and sterically distorted chromophore assemblies in poly(I). 1H‐ and 13C‐NMR spectroscopy of cyclobutane groups in poly(I) compared with that in the monomer model compound supported the conclusion derived from fluorescence study.
Cationic polyelectrolytes. III. Nitrile‐group reaction of macromolecular compounds with N,N‐dialkylaminoalkylamines
Authors: Drăgan Stela , Bărboiu V. , Petrariu I. , Dima M. 
Published: April 2003

AbstractThe chemical reaction in aqueous medium of polyacrylonitrile and acrylonitrile–vinyl acetate co‐polymer using asymmetrical diamines of H2N(CH2)mNR2 (m = 2,3) structure was studied. It was found that the nitrile group is modified to an dialkylaminoalkylacrylamide group; also determined were the reaction conditions required to obtain the highest degree of chemical transformation of the nitrile groups. All modified compounds were characterized by analytical spectroscopy (IR and 1H NMR) and by rheological methods. It was also established that glutaronitrile can be used as a low‐molecular‐weight model to study the chemical transformation of nitrile groups in polyacrylonitrile and related polymers.