bluuebunny/crossref_metadata_2025_split huggingface dataset:
γ Radiolysis of poly(4,4′‐isopropylidene diphenylene sebacate)
Authors: Gupta Mool C. , Srivastava Ashok K. 
Published: April 2003

AbstractPoly‐(4,4′‐isopropylidene diphenylene sebacate) (PIDPS), a condensation product of bisphenol‐A and sebacic acid, was irradiated with 60Co γ rays. Viscosity, end‐group analysis, and IR spectral measurement techniques were used to study the chemical changes occurring during γ radiolysis. It is observed that PIDPS undergoes random chain scission owing to weak links which may be present or be incorporated by the oxygen from air. The G value of random chain scission is estimated to be 9, whereas the enthalpy of fusion is found to be 6.2 kcal/mol repeat unit of PIDPS.
Polyaromatic ether‐ketones containing various biphenylene units as crosslinking sites
Authors: Sutter A. , Schmutz P. , Marvel C. S. 
Published: April 2003

AbstractPolyaromatic ether‐ketones were prepared from diphenyl ether, isophthaloyl dichloride, and small amounts of 2,6‐, 2,7‐, 1,5‐, and 1,8‐dicarboxylic acid chloride of biphenylene, respectively, by Friedel–Crafts reaction. Biphenylene units were incorporated as crosslinking sites. Crosslinking is achieved by curing the polymers at 310–350°C for several hours. While the uncured resins are soluble in concentrated sulfuric acid, the fully crosslinked polymers are completely insoluble.
Mechanism of alternating copolymerization of methyl methacrylate with styrene in the presence of diethylaluminum chloride
Authors: Zubov V. P. , Lachinov M. B. , Ignatova E. V. , Georgiev G. S. , Golubev V. B. , Kabanov V. A. 
Published: April 2003

AbstractA kinetic study of the propagation mechanism of the alternating copolymerization of styrene (St) with methyl methacrylate (MMA) in the presence of a complexing agent (diethylaluminum chloride, DEAC) in bulk and in tetrachloroethylene solutions at a molar ratio DEAC/MMA = 0.5 has been carried out. It has been shown that the copolymerization is a chain radical process characterized by a short active‐center lifetime, bimolecular termination, and high rate of chain transfer to the complexed MMA. A kinetic scheme has been proposed for the propagation mechanism of alternating copolymerization in the presence of a complexing agent not requiring independent measurements of the equilibrium constant of complexation. It has been found that spontaneous and UV‐initiated copolymerizations in the system have different mechanisms of initiation and a common mechanism of propagation. The propagation proceeds by addition of single monomers as well as donor‐acceptor complexes of the comonomers to the propagation radicals, with the first mechanism being predominant. Inclusion of the monomers in the complex leads to an increase of the St reactivity and to a decrease of the MMA reactivity in propagation to the corresponding macroradicals in comparison with the reactivity of the free monomers. A number of kinetic and statistical parameters of the propagation reaction have been calculated.
Plasma polymerization. VI. An ESCA investigation of the RF plasma polymerization of perfluoro‐2‐butyl tetrahydrofuran
Authors: Clark D. T. , Abrahman M. Z. 
Published: April 2003

AbstractPerfluoro‐2‐butyl tetrahydrofuran was polymerized by an RF glow discharge technique and detailed ESCA studies were made of the resultant films. The rate of film deposition was sensitively dependent on the W/FM parameter and the site of deposition. The ESCA data show that the molecular rearrangement accompanying plasma polymerization and the oxygen functionality is at a significantly lower level than the starting material. Under appropriate conditions plasma polymerization produces material with a C:F stoichiometry of 1:2, although the ESCA data show that the polymer is drastically different from PTFE. ESCA studies are also reported on thin films of the monomer studied at low temperature.
The chemistry and kinetic behavior of Cu‐Cr‐As/B wood preservatives. II. Fixation of the Cu/Cr system on wood
Authors: Pizzi A. 
Published: April 2003

AbstractThe kinetic behavior of a Cr6+/Cu2+ system in its reaction with wood has been elucidated. The same reactions with carbohydrates and lignin of wood for CrVI alone are still present. Approximately 20% of the copper is fixed to the guaiacyl units of lignin in the form of copper chromate; the remaining copper forms complexes with cellulose and mainly with the guaiacyl units of lignin. The CrVI/lignin guaiacyl unit complexes already found for the treatment of wood with CrO3 are still the main CrVI complexes formed. Copper chromate is present as [Cu(H2O)2(guaiacol)]CrO4(guaiacol) complexes, and CuCrO4 bridges between different guaiacyl units of the lignin network appear to be likely. Substantial interference of the Cu2+ ions in the second‐zone reactions of CrVI with wood occurs. The amount of CrVI and CrIII fixed onto lignin and cellulose compares well with experimental values. Rate constants, energies of activation, and Arrhenius equations of the various reactions have been obtained. The amount of Cu2+ interference in the reaction has also been calculated.
Quantitative NMR measurements in copolymers of vinylidene chloride and acrylonitrile: The effect of saturation and varying nuclear Overhauser enhancements
Authors: Henrichs P. M. , Hewitt J. M. , Schwartz L. J. , Bailey D. B. 
Published: April 2003

AbstractSpin‐lattice relaxation times and nuclear Overhauser enhancements (NOE) for 13C nuclei in copolymers of acrylonitrile and vinylidene chloride were measured at 20.1 and 67.9 MHz. In the CCl2 region of the spectrum T1 and NOE values of the various resonances are equal within experimental error and are invariant to changes in composition. The T1 and NOE values of the CCl2 region, however, are not equal to those of the CH or CN region. As a result compositions cannot be calculated by direct comparison of the areas in the CCl2 region and either the CH or the CN region. Discrepancies can be corrected for the CH resonances by multiplication of the area by an empirical constant. A similar constant for the CN region is composition‐dependent at 20.1 and 67.9 MHz. A chemical shift anisotropy mechanism is postulated as important for relaxation of the CN resonances. The overall influence of variable T1 and NOE values on quantitative determination of polymer composition is considered.
Water‐soluble copolymers. IV. Random copolymers of acrylamide with sulfonated comonomers
Authors: McCormick C. L. , Chen G. S. 
Published: April 2003

AbstractRandom copolymers of acrylamide with sodium‐2‐sulfoethyl methacrylate and with sodium‐2‐acrylamido‐2‐methylpropane sulfonate were synthesized in aqueous solutions utilizing persulfate initiators. Copolymer compositions were determined by elemental analysis and by infrared spectroscopic methods. Monomer reactivity ratios were calculated using Fineman–Ross, Kelen–Tüdos, and/or Mayo–Lewis techniques at appropriate conversions. The copolymer microstructure, including mean sequence length distributions, was calculated from reactivity ratios. Membrane osmometry and viscometry measurements were utilized to estimate molecular weight and size. The large dimensions of these polyelectrolytes in aqueous solutions, as well as their inherent hydrogen bonding capacity and pseudoplasticity, make these copolymers excellent candidates for application as mobility control agents in enhanced oil recovery.
Exactly alternating silarylene–siloxane polymers. II. The condensation polymerization of arylenedisilanols and bisureidosilanes
Authors: Dvornic Petar R. , Lenz Robert W. 
Published: April 2003

AbstractA new method for the preparation of exactly alternating silarylene–siloxane polymers by the low temperature step‐growth condensation polymerization reaction of arylenedisilanols and bisurei‐dosilanes in chlorobenzene was investigated. To obtain high molecular weight products 1H NMR spectroscopy and gel permeation chromatography were used to monitor the polymerization reaction. By using these procedures 12 different polymers were prepared from 1,4‐bis(dimethylhydroxysilyl)‐benzene, 4,4′‐bis(dimethylhydroxysilyl)phenyl ether, bis(1,1‐tetramethylene‐3‐phenylureido)‐dimethylsilane, and bis(1,1‐tetramethylene‐3‐phenylureido)‐methylvinylsilane monomers. The polymers were obtained in high yields, purities, and molecular weights.
Alternating copolymerization of α‐methylstyrene and maleic anhydride
Authors: Javni I. , Fleš D. , Vuković R. 
Published: April 2003

AbstractAlternating copolymers of α‐methylstyrene (α‐MeSt) and maleic anhydride (MAn) were prepared by free‐radical‐initiated polymerization in bulk, benzene, or butanone as solvents. By applying the generalized model described by Shirota and co‐workers, the reactivity ratios k1c/k12 and k2c/k21 were calculated from the change of copolymerization rate with monomer feed at constant total monomer concentration. From the equation Rp = Rp(f) + Rp(CT) were calculated Rp(f) and Rp(CT), and it was found that in benzene the reaction proceeds predominantly by the addition of CT‐complex monomers, while in butanone, cross propagation of free monomers predominates. Termination occurs predominantly by homotermination of α‐MeSt macro free radicals, kt22, although the cross termination kt21 is also operative.
Soapless emulsion polymerization of methyl methacrylate in water in the presence of calcium sulfite
Authors: Arai Masahiko , Arai Kunio , Saito Shozaburo 
Published: April 2003

AbstractA kinetic study performed on the polymerization of the MMA‐K2S2O8‐CaSO3‐H2O system shows that two different shapes of the time‐conversion curve were obtained according to the presence or absence of calcium sulfite powder in the reaction mixture. In the absence of the powder, the polymerization behavior is similar to that of the MMA‐K2S2O8‐H2O system reported earlier. An attempt was made to apply the kinetic model of the rate of polymerization and the self‐nucleation model of polymer particle formation in soapless emulsion polymerization to the present system. One is able to express the experimental time‐conversion curves reasonably well. The other can account for the number of polymer particles formed in polymerizations initiated with potassium persulfate alone or calcium sulfite alone but not that in polymerization initiated by both. In the latter case the rate of radical generation and the ionic strength were appreciably enhanced compared with the former. These enhancements might affect the mechanism of polymer particle formation; certain nucleations, such as an aggregative nucleation, might occur simultaneously in addition to the self‐nucleation. In the presence of the solid phase the time‐conversion curves were similar to that of emulsion polymerization rather than soapless emulsion polymerization, and the molecular weight of polymer formed was smaller than in the absence of the solid phase. It was shown experimentally that the rate of polymerization was remarkably enhanced by an increase in the solid content, whereas the molecular weight of polymer was only slightly affected. As a result, it is considered that calcium sulfite solid provides an important polymerization locus and probably also plays a significant role in radical generation.
Adhesive interface interactions between primary aliphatic amine surface conditioners and polyamic acid/polyimide resins
Authors: Linde H. G. 
Published: April 2003

AbstractThe interface reactions of 3‐aminopropyltriethoxysilane treated surfaces, with the polyamic acid/polyimide resin formed from pyromellitic dianhydride and oxydianiline, were defined in bulk reactant systems and by FTIR analysis on the surface layers of germanium internal reflection plates. Adhesion between these interfacial layers is the result of chemical bonding, which proceeds through initial carboxylate salt formation between the amino function of the silylated surface and the car‐boxylic acid present in the polyamic acid. Heating results in dehydration and amide formation, which is followed by preferential incorporation of the alkyl, surface‐bound amine (stronger base), over the aromatic polymer amine, in an imide linkage. Aromatic imides formed before or during thermal curing may also be preferentially opened in a modified Ing‐Manske reaction and reclosed to the more stable surface‐bound alkylimide. Apparently polymer scission at the aromatic amide linkages occurs in this adhesion process, preferentially bonding surface‐bound alkyl amines to one end of a shortened polymer chain.
Coenzyme models. 32. Catalytic activity of polymer‐bound thiazolium ions as estimated by flavin trapping technique
Authors: Shinkai Seiji , Hara Youichiro , Manabe Osamu 
Published: April 2003

AbstractThree thiazolium‐containing polymers, Th‐7, Th‐33, and Th‐18‐Py [where Th‐x and Py mean x mol % thiazolium unit and pyridinium unit (54 mol %), respectively], were synthesized from partially p‐chloromethylated polystyrene. The catalytic activities of these polymer catalysts in acyloin condensation of aldehydes and decarboxylation of α‐keto acids were estimated kinetically by oxidative trapping of the key intermediate by flavin (flavin‐trapping technique). In aqueous solution at 30°C, the catalytic activity of Th‐18‐Py and Th‐33 in condensation of p‐chlorobenzaldehyde was comparable with that of the cationic‐micelle‐bound thiazolium ion, whereas Th‐7 and a monomeric thiazolium compound (N‐benzylthiazolium bromide) scarcely exhibited any catalytic activity. The catalysis of the polymer‐bound thiazolium ions was sensitively suppressed by increased ionic strength. These results suggest that the pendent thiazolium ion is activated by the relatively high charge density along the polymer chain: the cationic environment is able to facilitate dissociation of the thiazolium ion to the ylid form and deprotonation of the thiazolium‐aldehyde adduct to the key intermediate.
Synthesis and properties of poly(imide‐sulfonate)s
Authors: Choi Kil‐Yeong , Choi Sam‐Kwon 
Published: April 2003

AbstractPolycondensations of N,N′‐bis(hydroxyalkyl)pyromellitic diimides, N,N′‐bis(hydroxyphenyl)‐pyromellitic diimides, N,N′‐bis(hydroxyalkyl)‐3,3′,4,4′‐benzophenonetetracarboxylic diimides and N,N′‐bis(hydroxyphenyl)‐3,3′‐4,4′‐benzophenonetetracarboxylic diimides with aromatic disulfonyl chlorides were carried out in pyridine to produce poly(imide‐sulfonate)s. The resulting polymers had inherent viscosities in the range of 0.25–0.38 dL/g. These poly(imide‐sulfonate)s were insoluble in common organic solvents and had relatively good thermal stability. The TGA data showed 10% weight losses at 253–365°C and residual weights at 500°C were 22–72% in nitrogen.
Studies on the kinetics of ceric–thiourea‐initiated aqueous polymerization of methyl methacrylate. I. Mechanistic features in moderately acid solution
Authors: Pramanick D. , Chatterjee A. K. 
Published: April 2003

AbstractThe kinetics of the aqueous polymerization of methyl methacrylate by a ceric‐thiourea initiator system in moderately acid solution (pH 2.15) was studied. The rate of polymerization was proportional to 0.41 power of ceric concentration, 0.32 power of thiourea concentration, and 1.18 power of monomer concentration. The degree of polymerization was smaller than expected from the rate of polymerization. Initiation efficiency was less than one. There was no evidence of any ceric ion termination in the concentration range of 2.50 × 10−4–2.00 × 10−3M studied. The results are explained in terms of partial primary radical termination; the principal mode of termination, however, was bimolecular.
Diffusion‐controlled vinyl polymerization. II. Limitations on the gel effect
Authors: Soh S. K. , Sundberg D. C. 
Published: April 2003

AbstractIt is frequently observed that the gel effect in vinyl polymerizations decreases in intensity at about the 50‐70% conversion level. This is apparent in both rate and molecular weight data. It is postulated that there should be a limitation on the decrease in the termination rate constant to explain this effect. As an extension of the general theory of chain length dependent termination behavior, a general treatment of the gel effect with a limiting value of the termination rate constant is presented. A specific model is proposed for this limited rate constant which is based on the simple consideration that as translational movement of macroradicals becomes increasingly difficult the contributions made by segmental motion derived solely from the propagation reaction will be the prevailing mechanism. The termination reaction changes from chain length dependent to chain length independent during this transition period.
Preparation and characteristics of photocross‐linkable poly(vinyl alcohol)
Authors: Ichimura Kunihiro , Watanabe Shoji 
Published: April 2003

AbstractThe reaction of poly(vinyl alcohol) with styrylpyridinium and quinolinium salts which contain formyl group produced water‐soluble photosensitive polymers. The sensitivity was high, although the content of the styryl groups was extraordinarily low. Spectroscopical studies revealed that the high sensitivity is due to the aggregation of photofunctional group in the polymer matrix which leads to cyclodimerization on exposure to ultraviolet (UV) light.
Mechanisms of pyrolysis for a specifically labeled deuterated urethane
Authors: Voorhees Kent J. , Lattimer Robert P. 
Published: April 2003

AbstractThe pyrolysis products of a model urethane prepared from trimethylolpropane (TMP) propoxylated with 3, 3, 3‐d3‐propylene oxide and PAPI have been extensively studied by gas chromatography in conjunction with electron‐impact, chemical‐ionization, and field‐ionization mass spectrometry. The isotope distributions for some of the lower‐molecular‐weight species (determined by electron‐impact and/or field‐ionization mass spectrometry) showed a greater amount of H/D mixing than was expected from previously postulated concerted mechanisms. The deuterium distributions of the higher‐molecular‐weight TMP species were, in general, consistent with previously described mechanisms. The results from this study support the proposal that pyrolytic degradation of urethanes occurs mainly by a systematic sequence of concerted reactions. However, the deuterium distributions in some compounds indicate that free‐radical reactions are important in the formation of some pyrolyzates.
Synthesis of aromatic polyamide‐phthalimidines from chloroformylphthalides and aromatic diamines
Authors: Imai Yoshio , Takahashi Takeyoshi , Ueda Mitsuru 
Published: April 2003

AbstractNew polymer‐forming monomers, 3‐benzylidene‐5‐chloroformylphthalide and 3‐benzylidene‐6‐chloroformylphthalide, were synthesized by the Perkin reaction of trimellitic anhydride with phenylacetic acid, followed by chlorination. The polycondensation of these monomers with aromatic diamines in N‐methyl‐2‐pyrrolidone at 200°C afforded aromatic polyamide‐phthalimidines having inherent viscosities of 0.2‐0.5 dL/g. All the polymers were readily soluble in m‐cresol, pyridine, dimethylformamide, and dimethyl sulfoxide. Glass transition temperatures of some of the polymers were in the range of 255–282°C. The polyamide‐phthalimidines began to lose weight at around 300°C in both air and nitrogen atmospheres, with 10% weight losses being recorded at 435–475°C in nitrogen by thermogravimetry.
Vinyl polymerization by lithium organocuprates
Authors: Han Y. K. , Park J. M. , Choi S. K. 
Published: April 2003

AbstractVinyl polymerizations initiated by lithium organocuprates under several conditions were investigated. It was observed that this catalyst was effective in the polymerization of specific monomers such as α,β‐unsaturated nitrile and carbonyl analogues. The rate of polymerization was rapid but retarded by the addition of pyridine, nitrobenzene, or hydroquinone. Polymerization of methyl methacrylate (MMA) with lithium di‐n‐butylcuprate as initiator produces predominantly isotactic poly(methyl methacrylate) (PMMA) in toluene. The overall activation energy was estimated as 3.5 kcal/mol deg. Lithium di‐n‐butylcuprate exerts a higher stereoregulating effect on the addition of monomers than other organolithium initiators. It is proposed that polymerization proceeds via a coordinated anionic mechanism.
Solvent effects on the synthesis of ion‐exchange membranes by radiation‐induced graft polymerization of methyl α,β,β‐trifluoroacrylate
Authors: Omichi Hideki , Okamoto Jiro 
Published: April 2003

AbstractMethyl α,β,β‐trifluoroacrylate (MTFA) was grafted onto polyethylene (PE) film and fluorine‐containing films to make ion‐exchange membranes. In the case of PE the grafting yield was not influenced by the presence of trifluorotrichloroethane (Freon 113) in the reaction mixture, while the presence of methanol decreased the grafting yield. The transversal distribution of graft chains in the film observed by electron‐probe x‐ray microanalysis showed that when the grafting was carried out in the presence of Freon the amount of graft chains in the central part of PE film was much larger than that at the film surface and that the grafts obtained in the absence of Freon were located mainly at the film surface. The electric resistance of the graft PE film obtained in the presence of Freon decreased more than that of the one obtained in the absence of Freon. The weight loss of the graft films in H2O2 solution was negligibly small.
Characterization of aromatic polymers (benzenoid and heterocyclic) by cross‐polarization, magic‐angle 13C‐NMR spectroscopy
Authors: Brown Charles Eric , Khoury Issam , Bezoari Massimo D. , Kovacic Peter 
Published: April 2003

AbstractThe cross‐polarization, magic‐angle 13C‐NMR spectra of solid samples of poly(p‐phenylene), its nitro derivative, polymerized biphenyl, poly(p‐phenylene sulfide), poly(1‐methyl‐2,5‐pyrrolylene), poly(1‐phenyl‐2,5‐pyrrolylene), poly(2,5‐thienylene), and poly(2,5‐selenienylene) and the high‐resolution 13C‐NMR spectrum of poly(m‐phenylene) in solution are presented and assigned. In all cases the chemical shifts are similar to those of model compounds in solution. In most instances the resonances of the nonprotonated carbon atoms in the solid polymers are more intense than those of the protonated carbons and appear to depend on the charge distribution in the molecular orbitals.
Plasma polymerization. VIII. A comparative study of the plasma polymers produced from inductively coupled plasmas excited in the fluorobenzenes
Authors: Clark D. T. , Abrahman M. Z. 
Published: April 2003

AbstractAn ESCA investigation has been made of the plasma polymers produced from the isomeric tri‐, di‐, and monofluorobenzenes in inductively coupled plasmas. Comparison is drawn with other published data on perfluoro‐, pentafluoro‐, and isomeric tetrafluorobenzenes. The data reveal that extensive molecular rearrangement accompanies polymerization and that proportionately the C:F stoichiometry shows a decrease in fluorine content relative to the monomer in going from perfluoro‐ to monofluorobenzene. Internal stress, critical surface tensions, and coefficients of friction are compared for the plasma polymers.
Functional monomers and polymers. XCVII. Synthesis of oligomer models of polyethyleneimine derivatives containing pendant thymine bases
Authors: Inaki Yoshiaki , Sakuma Yo , Suda Yasuo , Takemoto Kiichi 
Published: April 2003

AbstractA series of oligomer models of polyethyleneimine derivatives having pendant thymine bases were prepared by the reaction of carboxyethyl derivatives of thymine with oligomer amines using an activated‐ester method. It was found that the hypochromicity values obtained from UV spectra and pKa values obtained from spectrophotometric titrations depend on the chain length of the oligomers and the thymine content of the polymers.
Longitudinal volume viscosity of epoxide prepolymers
Authors: Lesbats J. P. , Legros R. , Aleman J. V. 
Published: April 2003

AbstractVolume flow of epoxide prepolymers and the effect of compression rate, temperature, and molecular weight on it are described. An increase in longitudinal volume viscosity with decreasing volume deformation, increasing compression rate, and increasing temperature has been observed. The molecular weight seems to have no influence.