bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and polymerizations of methyl 3,3‐difluorocyclobutene‐1‐carboxylate and methyl 3,3,4,4‐tetrafluorocyclobutene‐1‐carboxylate
Authors: Hall H. K. , Okamoto Y. , Padias A. Buyle , Deutschman A. , Berry J. W. 
Published: April 2003

AbstractTwo new monomers, methyl 3,3‐difluorocyclobutene‐1‐carboxylate (MDFC) and methyl 3,3,4,4‐tetrafluorocyclobutene‐1‐carboxylate (MTFC), were synthesized. Under free radical conditions, MDFC gave homopolymer; MTFC did not. Copolymerizations of these monomers showed them to behave as very electron‐deficient monomers, MTFC more so than MDFC. MDFC copolymerized with various vinyl ethers and styrenes to give high yields of almost 1:1 copolymers. Acrylonitrile copolymerized in lower yield with less incorporation of MDFC; trimethylethylenetricarboxylate did not copolymerize. Bicyclobutane‐1‐carbonitrile copolymerized well. MTFC copolymerized with the very electron‐rich monomers t‐butyl vinyl ether and p‐methoxystyrene, leading to alternating and nearly alternating copolymers, respectively, and even styrene tended to give almost 1:1 copolymers. Acrylonitrile gave only polyacrylonitrile, and trimethylethylenetricarboxylate did not react with MTFC under free radical conditions. The reaction of MTFC with the electron‐rich monomers t‐butyl vinyl ether and p‐methoxystyrene occurred spontaneously via charge transfer complexes. Thermally, the copolymers were rather stable, those of MTFC more so than those of MDFC.
The termination reaction in free radical copolymerization. I. Methyl methacrylate and butyl‐ or dodecyl methacrylate
Authors: Ito K. , O'driscoll K. F. 
Published: April 2003

AbstractUsing a spatially intermittent reactor, the absolute rate constant for the termination reaction in free radical copolymerization has been measured for the monomer pair methyl methacrylate (MMA)–butyl methacrylate (BMA). For the pair MMA–dodecyl methacrylate (DMA) the relative rate constant for termination has been measured. In both cases the termination rate constant was a monotonically changing function of the monomer feed composition. This function can be well approximated by a simple calculation of the enchained monomer units' contributions to the average segmental friction coefficient of the copolymer chain. An attempt to apply a previously derived theoretical treatment based on penultimate unit effects produced physically unrealistic results.
Stereochemistry in cationic polymerization of alkenyl ethers. III. Effect of the alkoxy group on the steric structure of polymers
Authors: Hirokawa Yoshitsugu , Higashimura Toshinobu , Matsuzaki Kei , Kawamura Tokiji , Uryu Toshiyuki 
Published: April 2003

AbstractPropagation mechanism in the cationic polymerization of alkenyl ethers was investigated through the effect of the bulkiness of alkoxy groups on the steric structure of a polymer. In polymerization with BF3O(C2H5)2 in toluene at −78°C, trans‐propenyl ethers having less bulky alkoxy groups–methyl, ethyl, and benzyl propenyl ethers–produced a stereoregular polymer having a threo‐meso structure, and the cis isomer a nonstereoregular one having threo‐meso and racemic structures. On the other hand, in the polymerization of propenyl ethers having bulky alkoxy groups–isopropyl and 1‐methylpropyl propenyl ethers–the trans isomer yielded a nonstereoregular polymer with threo‐meso and racemic structures, and the cis isomer a stereoregular one with a erythro‐meso structure. This result suggests that a bulky alkoxy group plays an important role in determining the steric structure of the polymer by repulsion between the alkoxy groups of a growing chain end and of a monomer. The effect of solvent polarity on the steric structure of a polymer was also studied.
Allylation of phenoxides by crown ethers and their polymers
Authors: Akabori Sadatoshi , Miyamoto Shigeo , Tanabe Hideo 
Published: April 2003

AbstractAllylation of sodium phenoxide in the presence of crown ethers produces a high ratio of O/O + C allylation when conducted in water, phenol, benzene, or diethyl ether. The striking increase in the product ratios is attributed to specific complexation of the crown ethers that facilitate the dissociation of the ion pair aggregate of the sodioderivative in benzene or diethyl ether. The crown ethers may act as a phase transfer catalyst when the reaction is run in water. Furthermore, the O/O + C ratios of the allylation strongly depend on the kind of crown ethers used. To examine their effect the allylation of sodium phenoxide was studied with various crown ethers, such as 18‐crown‐6, benzo‐18‐crown‐6, benzo‐15‐crown‐5, poly(vinylmonobenzo‐15‐crown‐5), and poly(vinylmono‐benzo‐18‐crown‐6), as catalysts. It was found that among these crown ethers poly(vinylmono‐benzo‐15‐crown‐5) was the most effective catalyst.
Stereoselectivity of the cyclooctene ring‐opening polymerization
Authors: Syatkowsky A. I. , Denisova T. T. , Ikonitsky I. V. , Babitsky B. D. 
Published: April 2003

AbstractThe stereoselectivity of the cyclooctene ring‐opening polymerization in the presence of the tungsten hexachloride–tetraisobutylalumoxane (TBAO) catalyst system has been studied. The reaction conditions have been established in which the polymer chain isomerization is reduced to a minimum. Under these conditions the stereoselectivity is determined by an individual act of the monomer molecule insertion. The dependence of stereoselectivity on monomer concentration, number of active sites, and temperature has been investigated. The results obtained suggest that the cyclooctene polymerization is selective in favor of the geometrical configuration of the starting cycloolefin (the “retention” effect) by analogy with the previously reported metathesis of acyclic olefins. Considerations which support the idea that cis and trans units are reproduced by the same type of active sites are discussed. The experimental evidence indicates that in this case the stereoselectivity is determined by the difference in kinetics of two reaction paths of the monomer molecule insertion that lead to the formation of cis and trans units.
Pyrolysis/Gas chromatography/mass spectrometry of polymers: Polyisopropenylcyclohexane and copolymers with its aromatic counterpart, α‐methylstyrene
Authors: Gritter Roy J. , Gipstein E. , Adams Gary E. 
Published: April 2003

AbstractFlash pyrolyses at 400, 650, and 900°C of polyisopropenylcyclohexane (PIC) and copolymers, produced by partial hydrogenation of poly‐α‐methylstyrene (PAMS), have shown that the decomposition of the PIC or IC sequences is complex. In comparison, PAMS and AMS sequences give only depolymerization to monomer at the two lower temperatures but a more complex degradation at 900°C, based on the products identified. It is interesting to note that traces of decalin solvent initiated the depolymerization of PAMS and the AMS sequences in the copolymers at 400°C. The products identified by copolymer pyrolyses indicated that no reaction occurred between S and IC units during decomposition. Average sequence data on the copolymers could not be determined because of the facile unzipping of the AMS sequences and the greater thermal stability of the IC sequences. The fragmentation pattern did indicate that partial hydrogenation of PAMS had produced random copolymer and not a blend of two homopolymers.
X‐Ray diffraction technique to assess radiation damage in semicrystalline polymers. I. Isotactic poly(methyl methacrylate)
Authors: Kusy R. P. , Greenberg A. R. 
Published: April 2003

AbstractBy using x‐ray diffraction the total damage to a semicrystalline polymer is determined after exposure to high‐energy ionizing radiation. By rearrangement of the first‐order dependence of the fractional change in crystallinity on the dose the number of chemical and/or physical changes per 100 eV of energy absorbed [i.e., G(–units)] is computed. In the present effort on isotactic poly‐(methyl methacrylate) (PMMA) the value of G(–units) ≈ 15 confirms previous results obtained by cryoscopy, and thereby yields a ratio of ca. 8:1 for chemical plus physical (i.e., total damage) versus chemical damage alone. From nuclear magnetic resonance (NMR) results, a partition of the physical damage into configurational and conformational changes yields G values of 6 and 7, respectively.
Influence of antimony catalysts with hydroxyethoxy ligands on polyester polymerization
Authors: Maerov S. B. 
Published: April 2003

AbstractThe effectiveness of antimony polymerization catalysts for polyester, with varying numbers of hydroxyethoxy ligands on antimony, was studied. The ligand number, ranked in decreasing effectiveness was 5 = 3 > 2 > 1 ≫ 0. Results for this series of compounds are consistent with a mechanism in which antimony bonds with polyester chain ends to catalyze intermolecular condensation.
Amorphous polyacrylonitrile: Synthesis and characterization
Authors: Joh Yasushi 
Published: April 2003

AbstractAmorphous polyacrylonitrile was successfully synthesized with bis(pentamethyleneimino)magnesium in heptane at 70°C. The amorphousness of the polymer increased with rising polymerization temperature and was favored by the nonpolar solvent. The polymer showed regular head‐to‐tail sequences which were confirmed by converting the polymer into polyacrylic acid and polymethylacrylate. The amorphous PAN produced a broad x‐ray diagram with a maximum at 2θ = 16.1° and a less intense halo at 2θ = 27.5°. This pattern did not change after heat treatment. The synthesis of amorphous PAN strongly supports Imai's hypothesis that polyacrylonitrile consists of paracrystalline and amorphous phases. The amorphous PAN also tends to support Minami's assignment of the two absorptions in the temperature dependence of the dynamic loss tangent; the absorption at the lower temperature (110°C) is due to molecular motions in the paracrystalline phase and the absorption at the higher temperature (160°C) is attributed to the molecular motions in the amorphous region.
Polyelectrolytes conformational probes: Auramine O and ethidium bromide interactions with hypercoiling maleic acid–olefin copolymers
Authors: Fenyo J. C. , Mognol L. , Delben F. , Paoletti S. , Crescenzi V. 
Published: April 2003

AbstractTwo cationic dyes—auramine O (AuO) and ethidium bromide (EBr)—have been tested for their ability to respond to conformational states of maleic acid–olefin copolymers in aqueous solution. The fraction of bound dye and the intensity of fluorescence of AuO are extremely sensitive to the presence of polyelectrolyte compact coils and to changes in ionic strength and counterion species. A related behavior is shown by the shift in the absorption visible spectrum of EBr, whereas its fluorescence seems to depend somewhat on the “structure” of the compact coils. These properties of the two dyes, which find a convincing correlation with viscosity and equilibrium thermodynamic data for the copolymers considered, are thus proved to be useful in probing the degree of compactness of polyelectrolyte coiled conformations in dilute aqueous solutions.
Investigations on the kinetics of copolymerization of vinyl acetate with acrylonitrile by Co(acac)3–Al(C2H5)3 catalyst system
Authors: Sharma Y. N. , Gandhi V. G. , Bhardwaj I. S. 
Published: April 2003

AbstractVinyl acetate and acrylonitrile were copolymerized with Co(acac)3‐Al(C2H5)3 catalyst system in benzene at 40°C. The rate of copolymerization is linearly proportional to monomer concentration and catalyst concentrations up to a certain value. The overall activation energy was found to be 11.3 kcal/mole. The effect of hydroquinone on the rate of copolymerization indicates the presence of free radicals in this system. The possibility of simultaneous formation of coordinate anionic and free radical active sites has been proposed.
Synthesis of poly(ester carbonate) copolymers
Authors: Prevorsek D. C. , Debona B. T. , Kesten Y. 
Published: April 2003

AbstractThe synthesis of poly(ester carbonate) copolymers based on bisphenol A, terephthalic acid, and phosgene is reviewed, and a new synthetic route is described leading to polymers which are different from those obtained by methods described in the literature. The most important features of the new method are quantitative incorporation of the dicarboxylic acid into the polymer and absence of undersirable side reactions. Synthesis of the random copolymer in which the dicarboxylic acid and carbonic acid groups are present in about equal molar amounts is discussed. Solution properties, effects of M̄n and copolymer composition on Tg, sequence length distribution, the effect of ester interchange reactions on molecular weight distribution, and effects of monofunctional chain termination on molecular weight of the final product are also discussed.
Functional monomers and polymers. LIX. Properties and function of Cu(II) complexes of the copolymers having pendant sulfide and imidazolyl groups
Authors: Sato M. , Shindo H. , Kondo K. , Takemoto K. 
Published: April 2003

AbstractThe Cu(II) complexes of copolymers having pendant sulfide and imidazolyl groups were prepared by a free radical copolymerization of ethylvinylsulfide with vinylimidazole, and their properties and function were studied spectrophotometrically in comparison with those of poly[4(5)‐vinylimidazole]. The complexes were found to be effective as catalysts for the oxidation of hydroquinone. Visible and ESR spectra of the Cu(II)‐copolymer complexes were similar to those of the Cu(II)‐homopolymer complexes, while the catalytic activity for the oxidation was different between these complex systems. A rapid reaction followed by a slow reaction, particularly at high ethylvinylsulfide content in the copolymers, was observed in the Cu(II)‐copolymer complex systems, but a continuous reaction proportional to the reaction time was observed in the Cu(II)‐homopolymer complex systems. The reoxidation rate of Cu(I) to Cu(II) complex, which was little affected by the concentration of imidazolyl group, decreased with a rise of the ethylvinylsulfide content in the copolymer. It was suggested that the sulfur atom of the sulfide group was weakly coordinated to Cu(II) but strongly to Cu(I), and an electron transfer reaction from substrate to the Cu(II) complex was increased, while reoxidation reaction of the Cu(I) complex was decreased in the copolymer complex systems.
Poly‐α‐ester degradation studies. VI. Thermal degradation of poly(3‐pentylidene carboxylate)
Authors: Cooper D. R. , Molloy R. , Sutton G. J. , Tighe B. J. 
Published: April 2003

AbstractThe thermal degradation of poly(3‐pentylidene carboxylate) has been studied kinetically over the temperature range 200–300°C using thermogravimetry, gas evolution analysis, and rheogoniometry together with isolation and analysis of the reaction products. The observed behavior is completely different from that previously reported for poly(isopropylidene carboxylate) and poly(methylene carboxylate). Whereas in the latter cases the decomposition occurs by a first‐order intramolecular ester interchange process characterized by an activation energy in the region of 27 kcal mole−1, poly(3‐pentylidene carboxylate) decomposition occurs by random chain scission superimposed on a first‐order hydrogen abstraction process. The activation energy associated with this decomposition reaction is in the region of 47 kcal mole−1, and the major degradation products are cis‐ and trans‐2‐ethyl crotonic acid.
Thermal cis–trans isomerization of cis–transoidal polyphenylacetylene
Authors: Simionescu C. I. , Percec V. 
Published: April 2003

AbstractSolution and solid‐state thermal cis‐trans isomerization of cis–transoidal polyphenylacetylene was investigated. At temperatures higher than 120°C, cis‐trans thermal isomerization in solution is accompanied by cyclization, aromatization, and scission of the polymer chain. Both spectral and kinetics data showed that at temperatures lower than 120°C, not only cis‐trans thermal isomerization takes place but also intramolecular cyclization.
Radiation‐induced polymerization at high dose rate. I. Isobutyl vinyl ether in bulk
Authors: Hayashi Kanae 
Published: April 2003

AbstractBulk polymerization of isobutyl vinyl ether was studied at 25°C in a wide dose rate range, 8.2‐277 rad/sec by γ rays and 8.8 × 103‐2.2 × 105 rad/sec by electron beams. At low dose rate, 8.2‐277 rad/sec, only the radical polymerization took place. At high dose rate exceeding 8.8 × 103 rad/sec, cationic polymerization was found to occur in addition to the radical polymerization. DPn of the product at high dose rate was 9‐10. Further drying of the monomer increased Rp, and molecular weight of the product formed by cationic mechanism also increased.
Thermal degradation of a series of polyester polyurethanes
Authors: Grassie N. , Zulfiqar M. , Guy M. I. 
Published: April 2003

AbstractA series of polyester polyurethanes with a range of polyester contents was prepared from an ethylene glycol/propylene glycol/adipic acid polyster, butane diol, and methylene bis (4‐phenyl isocyanate) (MBPI). They were thermally degraded under vacuum and the products of degradation were identified. The urethane linkages decompose first as the temperature is increased and the stability increases with polyester content. Reaction mechanisms were proposed which account for the principal features of the reaction and the products of degradation.
Polyacrylamide. I. Polymer content and hydrolysis level determination by potentiometric titration
Authors: St. Kenyeres J. , Ursu V. 
Published: April 2003

AbstractA method of determining the degree of hydrolysis by potentiometric titration of polyacrylamide (PAA) with HCl and NaOH was developed. From the titration curves and the control of the degree of purity it is possible to calculate the level of hydrolysis and the quantity of pure acid contained in the PAA of a commercial product.
Block copolymers of polystyrene and poly(dimethyl siloxane). I. Synthesis and characterization
Authors: Bajaj P. , Varshney S. K. , Misra A. 
Published: April 2003

AbstractThe block copolymers of the ABA type, poly(dimethyl siloxane‐b‐styrene‐b‐dimethyl siloxane), were synthesized by the anionic polymerization of styrene and cyclic siloxane monomer, hexamethyl cyclotrisiloxane (D3) or octamethylcyclotetrasiloxane (D4), with lithium or sodium biphenyl as initiator. The effect of initiator concentration, gegenion, and the polymerization temperature for styrene on molecular weight distribution (MWD) was investigated. Gel permeation chromatography (GPC) data show broader MWD of polystyrene prepared by sodium biphenyl in comparison to that produced by lithium biphenyl. The block copolymers have been characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectra. The influence of dimethylsiloxy units on thermal stability of the copolymers has also been discussed.
Copolymerization of liquid sulfur with certain olefinic systems and structure‐property studies on the polymeric materials
Authors: Bordoloi Binoy K. , Pearce Eli M. , Blight L. , Currell B. R. , Merrall R. , Scott R. A. M. , Stillo C. 
Published: April 2003

AbstractLiquid sulfur–olefinic reactions at 140°C forming crosslinked polysulfide polymers have been investigated. A systematic approach to the characterization and some structure–property studies on these new polymeric materials has been presented. The olefinic systems of interest are endo‐and exo‐dicyclopentadiene and an oligomeric alkenyl polysulfide. Equimolar S8–olefinic system copolymers are amorphous and they show no tendency for sulfur crystallization. A correlation has been drawn between chemical structure and glass transition temperature of the copolymers and terpolymers. Mechanical properties and, in particular, chemical stress relaxation of the crosslinked polysulfide polymers have been investigated.
2‐methyl‐3‐methylenecyclobutene‐1‐carbonitrile: A corrected structure and a new methylenecyclobutene monomer
Authors: Hall H. K. , Snider S. C. 
Published: April 2003

AbstractThe correct structure of the compound originally reported as 3‐methylene[2.1.0]bicyclopentane‐1‐carbonitrile is 3‐methylene‐2‐methylcyclobutene‐1‐carbonitrile. This new monomer undergoes free radical polymerization in the expected 1,5 manner.
New processable polyaromatic amides curable by intramolecular cyclization. XVI
Authors: Sankaran V. , Lin Shiow‐Ching , Marvel C. S. 
Published: April 2003

AbstractNew Processable Polyaromatic amides were prepared from 2,2′‐diiododiphenyl‐4,4′‐dicarbonyl dichloride (I) and several aromatic diamines. Phenylethynyl groups were introduced in these polymides by replacing the iodine groups with copper phenyl acetylide. On thermal curing, 2,2′‐di(phenylethynyl)biphenyl group undergoes intramolecular cyclization to form 9‐phenyl dibenzanthracene derivative. The cured polymers showed increased heat and chemical stabilities. No melting points were observed for all the polymers below 500°C. The viscosity of the polymers was decreased on substitution of the iodine by phenylethynyl groups.
Influence of the tacticity on thermal degradation of PVC. IV. Degradation in solution in comparison with degradation at solid state
Authors: Millan J. , Martinez G. , Mijangos C. 
Published: April 2003

AbstractFour fractions of PVC were obtained by successive extractions with appropriate solvents from PVC samples prepared in bulk at 60, 40, 0, and −50°C. Then they were carefully characterized, especially as far as stereoregularity is concerned. The samples were submitted to thermal degradation both at solid state and as solutions in dioctyl phthalate. The type of the polyene sequence distribution in degraded samples was determined by both the UV‐visible spectroscopy and the number of chain scissions resulting from the ozonization reaction. The degradation rate was proved to rise together with the syndiotactic sequence content in agreement with results in Parts I–III, obtained only with degradation at solid state. On the other hand, The content of the long polyenes relative to that of the short polyenes in the degraded polymers was found to be higher, and the number of chain scissions through ozonization reaction lower, when the syndiotactic sequence content is high. These results enable us to conclude that the actual mechanism of the PVC thermal degradation depends markedly on the tacticity distribution regardless of whether the degradation occurs either at solid state or in solution.
Reactions of stabilizer compounds. IV. ESR studies of the formation of stable nitroxyl radicals in the photooxidation of polypropylene containing hindered amine light stabilizers
Authors: Hodgeman Daryl K. C. 
Published: April 2003

AbstractESR studies of the formation of stable nitroxyl radicals in the photooxidation of polypropylene containing 2,2,6,6‐tetramethyl‐4‐hydroxypiperidine (II) and the commercial light stabilizer bis(2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate (III) are described. Spectra of the stable nitroxyl radicals in solid polymer and in solution after extraction from the polymer were obtained. The extract from photooxidized polypropylene containing the bifunctional stabilizer (III) showed only the mononitroxyl radical. The possible formation of polymer‐bonded nitroxyl radicals from (III) is discussed.
Sequence distribution in polyethylene/tetramethylene terephthalate copolyesters by 13C‐NMR
Authors: Newmark Richard A. 
Published: April 2003

Abstract13C‐NMR gives sequence information in copolyesters synthesized from ethylene glycol (EG), 1,4‐butane diol (BD), and methyl terephthalate (TP). The EG‐TP‐EG and BD‐TP‐BD blocks are distinguishable from the unsymmetrical diester sequence EG‐TP‐BD. The carbonyl and aromatic quaternary carbons of terephthalate have different chemical shifts but identical relaxation times and nuclear Overhauser enhancements in the three different triad sequences. Peak areas indicate random copolymerization of the three copolyesters studied.