bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure‐reactivity relations of conjugated and unconjugated monomers: Acrylates and methyl vinyl ketone in copolymerization with styrene compared with vinyl esters in copolymerization with ethylene
Authors: Schrijver J. , German A. L. 
Published: April 2003

AbstractThis article describes the copolymerization of methyl vinyl ketone (MVK), methyl acrylate (MA), and methyl methacrylate (MMA) with styrene (St) as reference monomer at 3.4 MPa and 335 K with toluene as solvent. In addition, the effect of pressure on the binary copolymerizations of St‐Ma‐MMA is discussed. It appearsthat in case of conjugated monomers reactivity decreases as the electron‐donating character of the substituents increases, whereas the reverse is found in unconjugated monomers. This is explained by the finding that in conjugated monomers resonance effects induced by polar factors play a dominant role, whereas in unconjugated monomers mainly polar factors are governing the relative reactivities. The r values at 3.4 MPa are compared with those predicted by means of the Q‐e scheme and Patterns. No definite conclusions could be drawn about the applicability and validity of either scheme, although Patterns shows excellent result in case of the H function of Mayo. In vinyl ester copolymerizations and Le Noble and Asano's example of the menshutkin reaction one single factor (polarity and steric hindrance, successively) dominates ΔG#, ΔG and ΔV#. This allows a straight forward interpretation of the result with the Hammond postulate and is in full agreement with Evan's potential‐energy calculations. In conjugated monomers, however, an interplay of reasonance and polar factors is found. The general validity of these findings needs further experimental and theoretical support.
Carbon‐13 NMR of 1,2‐polybutadienes: Configurational sequencing
Authors: Kumar Devendra , Rao M. Rama , Rao K. V. C. 
Published: April 2003

AbstractCarbon‐13 Fourier‐transform spectra (67.88 MHz) of 1,2‐polybutadienes (PBDs) (I–IV) were obtained. The triad and pentad intensities were calculated for the olefinic methylene carbon (C‐1). Bernoullian and first‐order Markov‐chain propagation statistics were tested to fit the experimental data. The pentad placements for the olefinic methine carbon (C‐2) were also assigned using the data calculated for the C‐1 carbon. Fine‐structure splitting due to placements higher than pentads was observed for both C‐1 and C‐2 carbons in PBD samples III and IV.
Azo initiators for the preparation of hydroxyl‐terminated polybutadienes
Authors: Idage B. B. , Vernekar S. P. , Ghatge N. D. 
Published: April 2003

AbstractAzo compounds such as di(4‐hydroxybutyl)‐2,2′‐azobisisobutyrate, di(3‐hydroxybutyl)‐2,2′‐azobisisobutyrate, di(2‐hydroxypropyl)‐2,2′‐azobisisobutyrate, and di(2‐hydroxyethyl)‐2,2′‐azobisisobutyrate were prepared and used as initiators for the preparation of hydroxyl‐terminated polybutadienes (HTPBs) of molecular weight (M̄n) ranging from 2000 to 7500 and functionality between 1.90 and 3.0. The polymers were prepared by free‐radical solution polymerization in dioxane and toluene. The polymers obtained were characterized for their molecular weight, hydroxyl number, functionality, and instrinsic viscosity.
Isomerization of polyamide prepared from bicyclic oxalactam
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi 
Published: April 2003

AbstractAnionic solution polymerization of bicyclic oxalactam, 8‐oxa‐6‐azabicyclo[3.2.1]octan‐7‐one (abbreviated as BOL), at 25°C yields the polyamide with both carbonyl and imino groups at the axial positions in the tetrahydropyran ring. On the other hand, the polyamide obtained by bulk anionic polymerization of BOL at 100°C has more complicated structures, probably due to the isomerizations and side reactions. The most frequent isomerization of the polyamide was the transfer of the carbonyl group adjacent to the tetrahydropyran ring from the equatorial to the axial position in the presence of base or acid catalyst at 25°C. Mechanisms are discussed from the viewpoint of the characteristic bonds in the polyBOL chain.
Polymerization of acrylonitrile initiated by a manganese(III) acetate glycerol redox system
Authors: Senapati Manjushree , Samal Narayan C. , Mishra Ranu , Tripathy Bibekananda , Rout Swoyam P. , Rout Mahendra K. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylonitrile(AN) initiated by manganese(III) acetate in the presence of glycerol was investigated in the temperature range of 30–40°C. The effect of varying the concentrations of glycerol, sulfuric acid, acetic acid, metal ion, and monomer on the rate was studied. A suitable reaction scheme and rate expression have been proposed. Termination was mutual and was caused by the combination of two growing polymer radicals.
Polymerization of cyclohexene oxide with aluminum complex/silanol catalyst. VI. Oligomer and polymer effects
Authors: Hayase Shuzi , Onishi Yasunobu , Suzuki Shuichi , Wada Moriyasu 
Published: April 2003

AbstractThe activity of an aluminum complex/polysilanol polymerization catalyst was examined in order to confirm the dependence of catalytic activation on silanol chain length. Tris (acetylacetonato)–aluminum/silanol increased when silanols with an intramolecular hydrogen bond such as the trimer of diphenylsilanediol, polydiphenyl(4‐vinylphenyl)silanol, and polymeric silanol of silicone were used. However, when tris(ethylacetoacetato)aluminum or tris(salicylaldehydato)aluminum was used, the product obtained from the reaction of a part of the aluminum complex with the polysilanols had to be considered in any explanation of the catalytic activation. The active catalyst with such aluminum complexes was obtained when the silanols that had intramolecular hydrogen bonds and gave the appropriate ratio of the reaction between the aluminum complex and silanol were used.
Synthesis of poly(vinylamine) containing asymmetric nucleic acid base derivatives as grafted pendants
Authors: Overberger C. G. , Kikyotani S. 
Published: April 2003

AbstractThe preparations of new model polymers of polynucleotides with stereoregular poly(vinylamine) (PVAm) backbones and an optically active nucleic acid base derivative as a pending side chain are described. The grafting of (±)‐, (+)‐, and (−)‐2‐(thymin‐1‐yl) propionic acid to linear PVAm prepared either by hydrolysis of poly(vinyl acetamide) or poly(vinyl‐t‐butyl carbamate) has proven to be more difficult than the case of polyethyleneimine. This may be due to a combination of the low solubility and steric factors of PVAm. PVAm formed a complex with oximes such as ethyl‐2‐hydroxyimino cyanoacetate (EHICA), which activates the amino group of PVAm; it became soluble in polar solvents and gave higher percent graft. These carboxylic acid derivatives were grafted onto PVAm through amide bonds by direct coupling with sulfonic acid esters of hydroxybenzotriazoles to give optically active graft polymers. These coupling agents were found to be much superior reagents than DEPC regarding racemization. The related monomer and dimer model compounds were also prepared by the same method from 3‐aminopentane and (−)‐, (+)‐, and meso‐2,4‐diaminopentane, respectively. The dimer models were separated and purified by HPLC to give models for isotactic, heterotactic, and syndiotactic polymer models. The enantiomeric purity of the optically active monomer model was determined by 360‐MHz NMR spectroscopy using optically active shift reagents.
Spectroscopic studies of poly(vinylamine) containing optically active thymine derivatives as grafted pendants
Authors: Overberger C. G. , Kikyotani S. 
Published: April 2003

AbstractThe optical properties of poly(vinylamine) containing optically active (+)‐ or (−)‐2‐(thymin‐1‐yl) propionyl groups as grafted pendants (PT) and the related monomer (MT) and dimer models (DT) were investigated by UV, circular dichroism (CD), and NMR spectroscopy. Highly syndiotactic PT has a smaller hypochromicity versus MT and a larger optical rotation than the less syndiotactic PT in various solutions. These results are attributed to an interaction between the configurational arrangement of thymines, the conformation of the polymers, and base stacking between thymines. The interactions of these polymers with poly(adenylic acid) (polyA) were also studied and the results compared with other vinyl‐type nucleic acid model polymers. The isomers of the optically active dimer models [prepared from meso and (dl)‐2,4‐diaminopentane] were separated. The CD spectra of (+)‐D(−)T in CHCl3 and trifluoroethanol (TFE) displayed extremely solvent‐dependent exciton coupling of the π–π* (B2u) transition of the base chromophore, which was not observed in the other models or polymers, except the meso‐type dimer model (meso)‐D‐(−)T. This coupling decreased with increasing solvent dielectric constant, while UV hypochromicity increased. This behavior as well as the 360‐MHz NMR spectra suggest that (+)‐D(−)T exists in an extended form in solvents of low dielectric constant and gradually assumes a stacked conformation as the dielectric constant increases.
Electrochemical electron‐transfer process of polymers containing N‐methylphenothiazine
Authors: Morishima Yotaro , Itoh Yoshihiro , Koyagi Atsufumi 
Published: April 2003

AbstractFor a fundamental study of the electrochemical behavior of electroactive polymers a series of poly(3‐vinyl‐10‐methylphenothiazine) (polyMPT), copolymers of 3‐vinyl‐10‐methylphenothiazine and methyl methacrylate (MMA) (copolyMPT), and 3‐ethyl‐10‐methylphenothiazine (EMPT) (a related monomer model) were prepared. The methylphenothiazine groups in these compounds showed reversible, one‐electron oxidation waves in the triangular‐were voltammograms. From a detailed comparison of the voltammograms between these polymers and EMPT it was revealed that the electroactive groups in poly MPT were not the “noninteracting” centers in the strict sense, whereas those in copolyMPT, in which the centers are spaced with the MMA segments, were typically noninteracting in nature; that is, in polyMPT the oxidation takes place at the potential 40 m V lower than that of EMPT and copolyMPT exhibited a wave identical to that of EMPT in shape and potential. The exhaustive electron transfer occurred from polyMPT to the electrode. On the other hand, a significant number of centers remained unoxidized in copolyMPT. The self‐exchange electron transfer within the polymer coil facilitates the exhaustive oxidation. For this event the proximity of the centers was an essential factor.
A study of the photochemical response of o‐nitrobenzyl cholate derivatives in P(MMA‐MAA) matrices
Authors: Reichmanis E. , Gooden R. , Wilkins C. W. , Schonhorn H. 
Published: April 2003

AbstractOrtho‐nitrobenzyl cholate esters have been successfully used as photosensitive components in solution inhibition deep UV photoresists. The photochemical behavior of a variety of substituted o‐nitrobenzyl cholate derivaties has been examined and resist sensitivity is related to the quantum yield of the reaction. The most efficient system examined is o, o′‐dinitrobenzyl cholate/P(MMA‐MMA), where the quantum yield of photoreaction is 0.2 and resist sensitivity is ca. 150 mJ/cm2 for a 1.5 μm film. The mode of resist behaviour on irradiation and development is also reported.
Melt spinning of syndiotactic 1, 2‐polybutadiene for preparation of carbon fibers
Authors: Ashitaka Hidetomo , Kusuki Yoshihiro , Asano Yukihiko , Yamamoto Shuji , Ueno Haruo , Nagasaka Akira 
Published: April 2003

AbstractThe thermal crosslinking and loss of vinyl unsaturation of syndiotactic 1, 2‐polybutadiene(s‐PB) at 180–230°C were prevented by stabilizers with 3, 5‐di‐t‐butyl‐4‐hydroxybenzyloxy group. The s‐PB samples (mp 140–198°C and MW 20,000–70,000) that contained the stabilizers could be melt‐spun at a temperature below 220°C into 1‐denier fibers to be used for the preparation of carbon fibers. The s‐PB fibers with higher mp and/or higher MW could be obtained by the addition of a high boiling solvent such as tetralin. The relationship between the molecular structures of s‐PB and the properties of resulting s‐PB fibers, including the degree of molecular orientation measured by birefringence and x‐ray diffraction, is presented. Spun fibers showed small swellings here and there along the fiber axis, which would have resulted from the inhomogeneity of the melt of s‐PB spun at a temperature slightly above the melting point. The gelation was unlikely to occur.
Polyaromatic ether‐sulfone‐ketones with fluorosubstituted p‐cyclophane units as crosslinking sites
Authors: Lin See , Marvel C. S. 
Published: April 2003

AbstractPolyaromatic either‐sulfone‐ketones containing fluoro‐substituted p‐cyclophane units were prepared from isophthaloyl chloride, terephthaloyl chloride, diphenyl ether, diphenoxydiphenyl sulfone, and a small amount of 1,1,2,2,9,9,10,10‐octafluoro‐[2,2]‐p‐cyclophane (type A) or pseudo‐p‐1,12,2,9,9,10,10‐octafluoro‐[2,2]‐p‐cyclophane bis‐acid chloride (type B) by Friedel‐Crafts‐type polymerization. The p‐cyclophane units were incorporated as crosslinking sites. Crosslinking was achieved by curing polymers at 300–350°C for several days. The polymers obtained, containing 1–10 wt % fluoro‐substituted p‐cyclophane units, were moderately soluble in dichloromethane, DMF, and sulfuric acid with inherent viscosities between 0.4 and 0.6. Laminates on glass fiber were made with excellent thermal stability.
The investigation of chemically crosslinked polypropylene by spin‐lattice relaxation time
Authors: Kunert K. A. , Jurkiewicz A. , Piślewski N. 
Published: April 2003

AbstractOur previous NMR investigations of chemically crosslinked polypropylene (PP) were focused mainly on testing the relation between NMR relaxation times as a function of crosslinking compound concentrations and the influence of structural factors found by this method on mechanical and other properties of this polymer.1,2 In these investigations, however, we did not consider the state of mobility of any part of the polypropylene chain under the influence of the network; therefore in this article we have attempted a clarification of this problem.
Optical activity of alternating copolymers of chiral α‐olefins with alkyl acrylates
Authors: Aglietto Mauro , Carlini Carlo , Veracini Carlo Alberto 
Published: April 2003

AbstractThe synthesis of high‐molecular‐weight substantially alternating copolymers of alkyl acrylates with optically active α‐olefins is reported. “Induced optical activity” on the side‐chain ester chromophores, depending on the chemical structure of the chiral α‐olefin, is indicated by CD measurements. Data are reported supporting the conclusion that this induced optical activity is related to a preferential chiral conformation of the macromolecules due to a cooperative effect.
Investigation of the structure of silk film regenerated with lithium thiocyanate solution
Authors: Bhat N. V. , Ahirrao S. M. 
Published: April 2003

AbstractThe Silk fibers of the mulberry (Bombyx Mori) were dissolved in a 70% lithium thiocyanate solution. Dissolved silk was regenerated by casting the films from the solution after dialyzing. The films were investigated by infrared (IR) spectroscopy and x‐ray diffraction analysis. It was found that the freshly prepared film was amorphous. The transformation to the β‐form could be brought about by heating, solvent induced crystallization, ultraviolet (UV) radiation, and prolonged storage. The mechanism of this transformation is discussed.
The synthesis of crosslinked copolymers of maleilated chitosan and acrylamide
Authors: Berkovich L. A. , Tsyurupa M. P. , Davankov V. A. 
Published: April 2003

AbstractBy acylating chitosan with maleic anhydride in formamide medium trisubstituted products (on one amine and two hydroxyl groups of the saccharide unit) have been obtained, as has been confirmed by IR spectroscopy, titration carboxylic groups, and determination of the content of olefin bonds. By copolymerizing trisubstituted maleilated chitosan and acrylamide in water solution crosslinked polymers have been obtained. Their swelling in water decreases with an increase in the share of maleilated chitosan in the initial mixture of reagents and with a decrease in dilution of the initial mixture of reaction components. Consumption of maleilated chitosan double bonds in this case varies from 40 to 70%.
Laser‐initiated copolymerization of maleic anhydride with styrene, vinyltoluene, and t‐butylstyrene
Authors: Sadhir R. K. , Smith J. D. B. , Castle P. M. 
Published: April 2003

AbstractLaser‐initiated polymerization of charge transfer monomer complexes has been investigated using an argon ion laser. The influence of solvents, monomer feed ratio, and irradiation time on the copolymer yield and composition was evaluated. The polymer yield was found to be directly proportional to the irradiation time and the molar concentration of maleic anhydride in the monomer feed. An enhanced rate of polymerization was obtained by substituting electron donating groups in the donor monomer. Polymerization, initiation, and propagation mechanisms, via charge transfer complexes, have been discussed. Comparison of laser‐induced polymerization with UV‐induced polymerization suggests that laser initiation is an energy‐efficient process.
Copolymerization of styrene with [(2‐methacryloyloxy)propoxy]trialkyl(aryl) silanes
Authors: Bajaj P. , Gupta D. C. 
Published: April 2003

AbstractStyrene was copolymerized with [(2‐methacryloyloxy)propoxy]‐trimethylsilane (2‐MAPTMS), [(2‐methacryloyloxy)propoxy]‐dimethylphenylsilane (2‐MAPDMPS), and [(2‐methacryloyloxy)‐propoxy]‐diphenylmethyl silane (2‐MAPDPMS) in toluene at temperatures between 60 and 90°C using azobisisobutyronitrile (AIBN) as initiator. The compositions of the copolymers were determined by silicon estimation. The reactivity ratios were calculated by the Kelen–Tüdös method. The reactivity ratio r1 (styrene) is higher for styrene‐2‐MAPDPMS than for the styrene‐2‐MAPDMPS and styrene‐2‐MAPTMS copolymerzation system. The difference between the activation energies E11 – E12 favors self‐propagation of the polystyryl radical, whereas the ratio of preexponential factors A11/A12 favors cross propagation. For the 2‐MAPTMS radical, the difference E22 – E21 favors cross propagation but the ratio A22/A21 favors self‐addition. The intrinsic viscosities and the theramal behavior of the copolymers were also studied.
Backbone‐assisted reactions of polymers. V. Kinetics of isomerization of poly(chloromethylthiirane) and poly(3‐chlorothietane) in solution
Authors: Zussman Melvin P. , Tirrell David A. 
Published: April 2003

AbstractThe reversible isomerization of poly(chloromethylthiirane) and poly(3‐chlorothietane) represents a new kind of polymer reaction and a new method of copolymer synthesis. In chloroform, in dichloromethane, or in nitrobenzene the reaction is well described by reversible first‐order kinetics. A rate increase of ca. 40% on changing the solvent from chloroform to nitrobenzene is consistent with an isomerization mechanism that involves a rate‐determining attack of the backbone sulfur atom on the neighboring carbon‐chlorine bond and rapid ring‐opening of the thiiranium ion intermediate by chloride ion.
Photocrosslinking of polymethoxymethylstyrene and copolymers containing (2,2‐disubstituted‐1,3‐dioxolan‐4‐yl)methoxymethylstyrene
Authors: Fukuda Hiroyuki , Nakashima Yoshihiro 
Published: April 2003

AbstractMethoxymethylstyrene (MSt), (2,2‐dimethyl‐1,3‐dioxolan‐4‐yl)methoxymethylstyrene (MMSt), and (2‐ethyl‐2‐methyl‐1,3‐dioxolan‐4‐yl)methoxymethylstyrene (EMSt) were synthesized and homopolymerized and copolymerized. The photochemical behavior of resultant homopolymers and copolymers with methyl methacrylate (MMA) and styrene (St) were investigated. The infrared (IR) and ultraviolet (UV) spectra of poly(MSt) showed that new bands ascribed to methyl benzoate residue increase rapidly with irrdiation time in air, but no detectable changes are observed in vacuum. The solubility measurements of poly(MSt) indicate that the main factor in crosslinking is the direct coupling of the benzyl radical generated by UV irradiation, which was confirmed by photopolymerization of MMA by means of benzyl methyl ether. It was also found that copolymers of MMSt or EMSt with MMA or St are easily crosslinked by UV irradiation. From the results of solubility measurements of these copolymers irradiated both in air and in vaccum, it was concluded that not only the 1,3‐dioxolane structure but also the benzyl methyl ether structure takes part in photocrosslinking, as we expected.
Copolymerization of vinyl acetate with ethyl α‐cyanocinnamate
Authors: Kharas Gregory , Kohn David H. 
Published: April 2003

AbstractTrisubstituted ethylene, ethyl α‐cyanocinnamate, is readily copolymerized with vinyl acetate by a conventional radical initiator. Terminal, penultimate, and “complex” copolymerization models were applied by using the data of composition of the copolymers obtained in bulk and by copolymerization in benzene, ethyl acetate, and chloroform. The model based on the participation of the monomer complexes describes satisfactorily the deviation from the terminal copolymerization model. The proton NMR analyses of the monomer mixtures indicate that the interaction between the monomers leads to the formation of weak monomer complexes. Kinetic studies of the initial rate dependence on the total monomer concentration and monomer feed composition enabled us to evaluate the degree of participation of the free uncomplexed monomers and the monomer complex in the propagation reactions. The contribution of the complexed monomers in the propagation stages increases with the increase in total monomer concentration. The initial rate of the copolymerization is proportional to the square root of the initiator concentration, thus confirming the bimolecular termination of the macrochains. The rate constants of the addition reactions of the complex and free monomers were evaluated from the kinetic studies. The quantitative kinetic treatment provided information regarding the relative weight of the termination reaction and indicated that the termination in the system occurs predominantly by the cross‐termination reaction between two growing polymer radicals with different kinds of monomer units at the ends. Additional information on the termination in this system was obtained from viscosity measurements.
Metal(II) 4,4′,4″,4′″‐phthalocyanine tetramines as curing agents for heat resistant epoxy formulations
Authors: Achar B. N. , Fohlen G. M. , Parker J. A. 
Published: April 2003

AbstractPure metal(II) 4,4′,4″,4′″‐phthalocyanine tetraamines (MPTA) have been used to cure epoxy resins in a homogeneous reaction. Infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analytical studies were used to characterize these materials and to evaluate the optimum curing conditions. Considerable improvement in the heat resistance of the epoxy resin cured with MPTA over those cured with other commonly used curing agents was observed. This was expected from the highly aromatic structure of the phthalocyanines. A noteworthy feature of these cured materials is their high anaerobic char yield, 73.5–75%, higher than in any heretofore known cured epoxy systems. Preliminary mass spectral studies on the cured polymers are presented.