bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co‐oligomerization of ethylene and higher linear alpha olefins. I. Co‐oligomerization with the sulfonated nickel ylide‐based catalytic system
Authors: Kissin Y. V. 
Published: April 2003

AbstractCo‐oligomers of ethylene and a series of linear α‐olefins (propylene, 1‐butene, 1‐hexene, 1‐heptene, 1‐octene, and 1‐decene) were synthesized with a homogeneous catalyst consisting of sulfonated nickel ylide and diethylaluminum ethoxide at 90°C. GC analysis of the co‐oligomerization products allowed complete structural identification of all reaction products, α‐olefins with linear and branched chains, vinylidene olefins, and linear olefins with internal double bonds. The article describes the reaction scheme of ethylene–olefin co‐oligomerization. The scheme includes chain initiation reactions (insertion of ethylene or an olefin into the NiH bond), chain propagation reactions, and chain termination reactions via β‐hydride elimination. Primary and secondary inertions of α‐olefins into the NiH bond in the initiation stage proceed with nearly equal probabilities. Higher olefins participate in the chain growth reactions (insertion into the NiC bond) also both in primary and secondary insertion modes. The primary insertion of an α‐olefin molecule into the NiC bond produces the β‐branched NiCH2CR1R2 group. This group is susceptible to β‐hydride elimination with the formation of vinylidene olefins. However, the NiCH2CR1R2 groups can participate in further ethylene insertion reactions and thus form vinyl oligomerization products with branched alkyl groups. On the other hand, the secondary insertion of an α‐olefin molecule into the NiC bond produces the α‐branched NiCR1R2 bond which does not participate in further chain growth reactions and undergoes the β‐hydride elimination reaction with the formation of linear reaction products with internal double bonds. Most co‐oligomer molecules contain only one α‐olefin fragment. However, the analysis of ethylene‐propylene and ethylene‐1‐heptene co‐oligomers allowed identification of products with two olefinic fragments which are also formed in the copolymerization reactions with small yields.
Synthesis and thermal self‐crosslinking reaction of polymer containing spiro ortho ester and carboxylic acid
Authors: Isobe Naoki , Numasawa Hideki , Nishikubo Tadatomi , Togoshi Hirotaka , Endo Takeshi 
Published: April 2003

AbstractPolymers with both pendant spiro ortho ester and carboxylic acid moieties were synthesized by partial esterification of poly(methacrylic acid), poly(methacrylic acid‐co‐methyl methacrylate), or poly(methacrylic acid‐co‐styrene) with halomethylated spiro ortho esters in the presence of 1,8‐diazabicyclo[5,4,0]undecene‐7 in dimethyl sulfoxide. The extent of esterification increased with increasing reaction temperature. The reaction of polymeric carboxylic acids with chloromethylated spiro ortho esters proceeded to 80% of conversion at 100°C for 120 h. In contrast, the degree of esterification with bromomethylated spiro ortho ester reached 80% at 60°C within 24 h. Thermo‐crosslinking of polymers having pendant spiro ortho ester moiety and carboxylic acid could be effected in films. The rate of spiro ortho ester ring‐opening increased with increasing reaction temperature and with increasing content of carboxylic acid groups in the polymer. Further, the rates of gel production were also measured. The polymer containing an equimolar mixture of spiro ortho ester moieties and carboxylic acids exhibited the highest reactivity. In addition, it was found that thermal crosslinking reaction of the polymer occurred with minimum volume shrinkage.
Microstructure of poly(alkylene phosphates) related to biopolymers (teichoic acids)
Authors: Biela Tadeusz , Kłosiński Paweł , Penczek Stanisław 
Published: April 2003

AbstractThe microstructure of polyphosphites and polyphosphates obtained by the ring‐opening polymerization of asymmetrically substituted 5‐membered cyclic phosphites was studied. It has been established, using 31P NMR, that 4‐substituted 2‐hydro‐2‐oxo‐1,3,2‐dioxaphospholanes underwent polymerization giving polymers with head‐to‐tail dyads as well as head‐to‐head and tail‐to‐tail structures. Analyses of 31P NMR spectra of racemic and optically active poly(2‐hydro‐4‐methyl‐2‐oxo‐1,3,2‐dioxaphospholane) and model compounds estimated the statistical mode of ring scission of cyclic phosphites. Similar results were obtained for the polymerization of 4‐acetoxymethyl‐2‐hydro‐2‐oxo‐1,3,2‐dioxaphospholane, which provided the simplest model of teichoic acid, namely poly(1,2‐glycerol phosphate).
The polymerization of isobutylene by AlCl3 in CH2Cl2 and the role of CH2Cl2 in the initiation reaction
Authors: Toman L. , Spěváček J. , Pokorný S. 
Published: April 2003

AbstractA solution of AlCl3 in CH2Cl2 prepared in advance was used 18 days after the mixing of the components as an initiation system in the polymerization of isobutylene performed in CH2Cl2 in the temperature range between −10 and −20°C. The 1H‐NMR analysis of polyisobutylene (PIB) samples synthesized to low and high conversion showed that it is the initiation reaction and not the transfer reaction to dichloromethane that is responsible for the CH2Cl endgroup in the polymer chain. In case of the transfer to monomer formation of PIB with internal terminal unsaturation [PIBCHC(CH3)2] is preferred to external unsaturation [PIBCH2(CH3)CCH2]. The solutions of AlCl3 in CH2Cl2 showed an absorption band at λmax = 302 nm.
New elastomeric networks based on functionalized ethylene–propylene rubbers and hydroxyl terminated polybutadiene. I. A kinetic study on the monoesterification
Authors: Immirzi Barbara , Laurienzo Paola , Malinconico Mario , Martuscelli Ezio 
Published: April 2003

AbstractEthylene–propylene random copolymers bearing grafted succinic anhydride functions have been reacted with an α,ω‐hydroxyl telechelic polybutadiene to obtain elastomeric interpolymer complexes. A kinetic study has been carried out by infrared techniques to study the influence of the addition of catalyst, stoichiometry, and temperature on the degree of monoesterification reaction.
The electrocopolymerization of styrene with vinyl acetate in an organic solvent
Authors: Calafate Bettina A. L. , Garcia Maria Elizabeth F. , Mano Eloisa B. 
Published: April 2003

AbstractCopolymers of styrene and vinyl acetate were synthesized electrochemically. The reaction system was composed of methylene chloride as the solvent, and a quaternary ammonium salt as the electrolyte. The reactions were run in a divided cell and the influence of current strength, reaction time, and temperature on the yield, molecular weight, and chemical composition of the resulting copolymers was investigated. It was found that the polymer chains were composed mainly of styrene units.
Quinone–amine polymers. II. 1,3‐bis(3‐aminophenoxy) benzene‐p‐benzoquinone oligomers
Authors: Kaleem K. , Chertok F. , Erhan S. 
Published: April 2003

AbstractA novel oligomeric compound has been synthesized by reacting 1,3 bis‐(3‐aminophenoxy)‐benzene (APB) with p‐benzoquinone. A dark reddish brown product has been characterized using UV, IR, and NMR spectra, and elemental analysis. It, too, adheres to metals, as does another polyetheramine‐p‐benzoquinone polymer synthesized in Part I [Prog. Org. Coating, 15, 63 (1987)], and becomes nonwettable after heat curing. However, its moisture adsorption is only 0.1% by weight, as against 3% for the latter product. This makes it a likely candidate for insulating electronic components from moisture.
Superactive and stereospecific catalysts. III. Definitive identification of active sites by electron paramagnetic resonance
Authors: Chien James C. W. , Hu Youliang 
Published: April 2003

AbstractSuperactive Ziegler–Natta catalysts have been prepared from a soluble MgCl2·2‐ethyl hexanol adduct in the presence of organic esters through reactions with TiCl4 and activated with AlEt3/phenyltriethoxy‐silane. Electron paramagnetic spectra (EPR) were used to elucidate the nature and amount of those Ti+3 ions not bridged to another Ti+3 ion; the chlorine bridged Ti+3 ions are EPR silent. The EPR spectra were attributed to two rhombic Ti+3 sites with principal values for the g‐tensors (1.967, 1.949, 1.915; and 1.979, 1.935, 1.887). The total amount of the EPR species, obtained by double integration of the EPR spectra, is in close agreement with the concentration of isospecific catalytic sites determined by radiotagging. This suggests that the nonspecific sites are EPR silent. When o‐phthalic ester was present during the catalyst synthesis, there appears an EPR signal at the free electron g‐value. This signal was attributed to a Ti+3 phthalate species with resonance stabilization and spin delocalization; it is absent in the catalysts made in the presence of monoesters such as ethyl benzoate. The effects of monomer, O2, H2O, and I2 on the EPR spectra were investigated. The changes in the EPR spectral intensity and the total Ti+3 ions, the latter determined by redox titrations during a polymerization or catalyst aging, are described. The results were extensively compared with those observed for supported Ziegler–Natta catalyst prepared with crystalline MgCl2.
Dithiafulvene (1,3‐dithiole): Monomers and polymers
Authors: Mulvaney J. E. , Figueroa Francisco R. , Evans Stacy B. , Osorio Fritz V. 
Published: April 2003

AbstractMonomers and polymers of 2‐benzylidene‐1,3‐dithioles (dithiafulvenes) were synthesized. Polymerization of substituted dithiafulvenes with diacid chlorides, p‐phenylene diisocyanate, or terephthalaldehyde yielded yellow polymers with inherent viscosities ranging from 0.10 to 0.21 dL/g.
Preparation and properties of polyarylates and copolyarylates from phenylindanedicarbonyl chloride and bisphenols
Authors: Yoneyama Masaru , Kuruppu K. D. Athula , Kakimoto Masa‐aki , Imai Yoshio 
Published: April 2003

AbstractA series of polyarylates having inherent viscosities of 0.4–1.1 dL/g was prepared by the two phase polycondensation of 1,1,3‐trimethyl‐3‐(4‐chloroformylphenyl)indanecarbonyl chloride with various bisphenols in an organic solvent–aqueous alkaline solution system in the presence of a phase transfer catalyst. Similarly, copolyarylates of high molecular weights were prepared from a mixture of the phenylindanedicarbonyl chloride, terephthaloyl chloride, and 2,2‐bis(4‐hydroxy‐phenyl)propane. All the polyarylates were characterized by their amorphous nature and high solubility in organic solvents. They gave transparent and tough films by the solution casting. The films had tensile strength of 33–46 MPa, elongation at break of 3–16%, and tensile modulus of 1.2–1.6 GPa. These polyarylates had glass transition temperatures in the range of 205–310°C, and began to decompose at ca. 350°C in air.
Synthesis of regiospecifically meta‐substituted poly(phenylacetylene)s and some of their electrical properties
Authors: Chang Tak‐lung , Holzknecht L. J. , Mark Harry B. , Ridgway Thomas H. , Zimmer Hans 
Published: April 2003

AbstractThe syntheses, characterizations, and electrical properties of four regiospecifically substituted poly(phenylacetylene)s are described. Tungsten(VI) chloride/tetra‐n‐butyltin (WCl6/n‐Bu4Sn) catalyst system (Higashimura–Masuda, H.–M. catalyst) was used to polymerize 3‐bromo‐, 3‐chloro‐, 3‐trimethylsilyl‐, and 3‐trimethylstannylphenylacetylenes in order to obtain high‐molecular‐weight and soluble materials. Characterizations of these polymers were done by IR and UV spectroscopic methods, GPC, DSC, and elemental analysis. The electrical conductivities of the polymers were measured on the surface of pressed pellets by a four‐point probe.
Pyrolysis–gas chromatography mass spectrometry and field ionization mass spectrometry of polyquinones
Authors: Blazso Marianne , Jakab Emma , Szekely Tamas , Plage Bernd , Schulten Hans‐rolf 
Published: April 2003

AbstractLow‐ and high‐molecular mass thermal decomposition products of five polyquinones with different linking aromatic structures have been analyzed by pyrolysis–gas chromatography and by direct (in‐source) pyrolysis–field ionization mass spectrometry. The quantity of carboxyl groups present in the polymer is obtained by the amounts of carbon dioxide found by pyrolysis–gas chromatography. Assuming a radical thermal decomposition mechanism the distribution of ketoacidic and quinonoid segments along the macromolecular ladder could be estimated from the high‐molecular mass products measured by pyrolysis–field ionization mass spectrometry. A random distribution of the two different segments was found for polyquinones with biphenylene and dibenzofuran subunits, while a structure built up of blocks of two or more identical segments was obtained for polyquinones with dibenzothiophene and diphenylmethane subunits. At the same time the anomalous structural moieties in the polyquinone ladders are also clarified with the help of the identification of the unexpected pyroysis products. Oxidated and bis‐dibenzothiophene and bis‐diphenylmethane subunits were found. The observed temperature dependence for the appearances of the thermal degradation products indicates that condensation and elimination reactions are taking place under the described pyrolysis conditions. Condensation in the ketoacidic segments forming new quinonoid segments proved to be important in the polymer which was a 100% poly(ketoacid), but negligible in the polyquinones containing ketoacidic segments up to 60%.
Associative organotin polymers. I. Symmetric trialkyltin fluorides: Synthesis and properties
Authors: Dandge D. K. , Taylor C. , Heller J. P. 
Published: April 2003

AbstractFour novel symmetric tri‐n‐alkyltin fluorides were prepared. In this homologous series, melting point decreases with increase in the carbon chain length while an x‐ray diffraction study shows an increase in amorphousness. 1H‐NMR spectra in cyclohexane, a nonpolar solvent in which these compounds form long polymeric chain, show a peak broadening effect due to high solution viscosity at very low solute concentration. Contrary to this, the spectra in CDCl3, a polar solvent in which these compounds are monomeric, show well resolved and narrow peaks. IR frequencies for SnC vibrations have been assigned.
A theory of green strength in polyisoprene
Authors: Cameron A. , McGill W. J. 
Published: April 2003

AbstractIt is shown that, at −25°C, natural rubber (NR) crystallizes more readily than synthetic polyisoprene (IR), the long induction period for nucleation in IR in particular being dependent on the carbon black loading. Both elastomers form bound rubber with carbon black but not with nonreinforcing fillers such as CaCO3 and glass powder. At room temperature, in the presence of carbon black, NR has good green strength but not IR, while neither rubber has good green strength with nonreinforcing fillers. However, at 0°C CaCO3 filled NR too has good green strength. A theory is proposed to account for the good green strenth characteristics found with certain compounds. In the model rubber molecules, already bound to the carbon black surface, are linked together, at low strains, via stress‐induced crystal lamellae, giving a three‐dimensional network in the compound. Such crystal lamellae are known to grow at right angles to the direction of strain from row nuclei formed at low strains. The coherence provided by the network permits the formation, at higher strains, of stress‐induced crystals in which polymer chains are now aligned in the direction of strain. This leads to an upturn in the stress–strain curve. In the absence of either bound rubber or of crystal lamellae, a long range network structure cannot form and extension of the sample continues at constant stress.
Synthesis and characterization of poly(amide‐sulfonamide)s
Authors: Adduci Jerry M. , Amone Michael J. 
Published: April 2003

AbstractNovel poly(amide‐sulfonamide)s have been prepared by reacting terephthaloyl, isophthaloyl, and sebacoyl chloride with variously substituted dianilines containing preformed sulfonamide linkages. Inherent viscosities of the prepared polymers ranged from 0.19 to 0.58 dL/g. Despite low apparent viscosities, the polymers had film forming properties. Clear, tough, flexible films were obtained from the prepared polymers, in particular the poly(terephthalamide‐sulfonamide)s. Glass transition temperatures, determined by differential scanning calorimetry, ranged from 84 to 247°C. Thermogravimetric analyses of the polymers showed that they have moderate thermal stability with weight losses ranging from 12 to 35% at 350°C.
Second‐order kinetics of enthalpy recovery in polystyrene
Authors: Chang Benjamin Tai‐An , Li J. C. M. 
Published: April 2003

AbstractSecond‐order kinetics were found applicable to the isothermal enthalpy release after quenching from a high temperature. The kinetic behavior was unaffected by different amounts of initial excess enthalpy. The activation enthalpy obtained from the temperature dependence of the second order rate constant was 200 kcal/mol or 837 kJ/mol which could be compared with 736 kJ/mol for volume recovery in a similar temperature range relative to Tg.
Analysis of plasma polymerization of allylamine by FTIR
Authors: Krishnamurthy V. , Kamel Ihab L. , Wei Yen 
Published: April 2003

AbstractThe plasma polymerization of allylamine in an inductively coupled rf plasma reactor is analyzed by Fourier transform infrared spectroscopy. Comparison of the infrared spectra of the as‐received monomer and the plasma polymerized film reveals a conversion of the primary amine in the monomer (CH2NH2) to an imine (CHNH) and a nitrile (CN). Plasma polymerization of ethylenediamine yields the same results, suggesting that this polymerization scheme may be typical of primary amines. Increasing the plasma power seems to increase the proportion of nitrile groups in relation to the imine groups. The infrared spectra of the vapor phase polymerized monomer was similar to that of the substrate‐grafted allylamine film implying a similar structure. Aging of this vapor phase polymer at 120°C for 1 h in vacuum and at 295°C for 15 min in an oxygen free environment reveals nitrile group reaction similar to that observed in polyacrylonitrile. Thermogravimetric analyses of the vapor phase polymers in a nitrogen atmosphere at 20°C/min demonstrated the thermal stability, with the polymer produced at a plasma power level of 50 W retaining 20% of its weight at 1000°C. This was better than the stability shown by the polymer produced at 150 W and is attributed to the ease of nitrile group polymerization in the former.
Synthesis of poly(methyl methacrylate) macromonomer
Authors: Ishizu Koji , Fukutomi Takashi 
Published: April 2003

AbstractAnionic polymerization of methyl methacrylate (MMA) was carried out in tetrahydrofuran (THF) or THF/toluene mixture at −78°C initiated by triphenylmethyl sodium or lithium as initiators. Highly syndiotactic PMMA of low polydispersity (Mw/mn = 1.11–1.17) could be prepared with triphenylmethyl lithium in THF or THF/toluene mixture at − 78°C. Moreover, PMMA macromonomer having one vinylbenzyl group per polymer chain was prepared by the couplings of living PMMA initiated by triphenylmethyl lithium with p‐chloromethyl styrene (CMS) at −78°C. The coupling reaction of living PMMA initiated by triphenylmethyl sodium with CMS was scarcely occurred.
Wavelength sensitivity of acrylonitrile–butadiene–styrene
Authors: Searle N. D. , Maecker N. L. , Crewdson L. F. E. 
Published: April 2003

AbstractThe wavelength sensitivity of unpigmented 100 mil thick ABS exposed to sunlight and filtered xenon are radiation was determined by the sharp cut filter technique based on three types of photochemical changes: bleaching, yellowing and loss in impact strength. Bleaching of the yellow‐colored species formed in the processed material is caused by wavelengths between 380 and 525 nm with maximum color change by the 475–485 nm region. Photochemical yellowing is due to wavelengths between 300 and 380 nm with all wavelengths being almost equally effective. The spectral sensitivity based on change in impact strength shifts from the UV to the visible region as photochemical yellowing progresses. Addition of two stabilizers, a benzotriazole ultraviolet absorber and a hindered amine stabilizer, shifts the wavelength sensitivity based on yellowing to wavelengths shorter than 330 nm, but has no influence on the spectral effects based on impact strength. It is postulated that the rate of yellowing is reduced mainly by the ultraviolet absorber and stabilization against loss in impact strength is due largely to the hindered amine. Differences in rates and spectral response of the three types of photochemical changes indicate that they are due to different initiating mechanisms and thus require different types of stabilization. The significance to stability testing is discussed.
Molecular motions of tactic poly(2‐hydroxyethyl methacrylate) in solutions studied by 13C‐NMR relaxation measurement
Authors: Oh Seok Heon , Ryoo Ryong , Jhon Mu Shik 
Published: April 2003

AbstractThe spin‐lattice relaxation time and the nuclear Overhauser enhancement were measured using Bruker AM 300 spectrometer operating at 75.5 MHz for 13C to investigate the molecular motional characteristics and its tacticity effect for tactic poly(2‐hydroxyethyl methacrylate) (PHEMA) as a function of temperature in dimethyl sulfoxide and methanol solvents. The observed relaxation data have been analyzed for both backbone motion and methyl internal rotation according to the log‐χ2 distribution model and the diamond‐lattice model. The correlation times thus obtained for the molecular motions show that isotactic PHEMA is more flexible than syndiotactic counterpart. The syndiotactic PHEMA seems to have intramolecular hydrogen bonding which restricts the motion of C‐2 carbon at temperatures below 35°C, whereas the isotactic one indicated no hydrogen bonding at all temperatures examined in this study. The methyl group of isotactic PHEMA shows a greater degree of freedom for the internal rotation than that of syndiotactic one. From the temperature dependence of correlation times, the activation energies for both backbone segmental motion and methyl internal rotation are obtained. The activation energies, 20 kJ/mol for backbone motion and 19 kJ/mol for methyl internal rotation, for isotactic PHEMA are substantially lower than the corresponding activation energies of 30 and 32 kJ/mol obtained for syndiotactic one. An examination of these energies indicates that methyl side group and backbone motions in tactic PHEMA are linked together.
Synthesis, characterization, and kinetics studies of organic soluble photosensitive copolyimide
Authors: Lee Hurng‐Rern , Lee Yu‐Der 
Published: April 2003

AbstractA copolyimide synthesized from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, 3,5‐diaminobenzoic acid, and 2,3,5,6‐tetramethyl‐p‐phenylene diamine was found to be soluble in N‐alkyl substituted amides. An organic soluble photosensitive polyimide was obtained by further reaction of the copolyimide with methacrylic acid glycidyl ester. After adding Michler's ketone, the UV spectra absorbance near 360 nm of the copolyimide decreased rapidly upon the irradiation of mercury lamp. Using benzoic acid and methacrylic acid glycidyl ester as model compounds and N, N‐dimethylbenzylamine as catalyst, the mechanism of reaction between the carboxylic group of the copolyimide and epoxy group of methacrylic acid glycidyl ester in N‐methyl‐2‐pyrrolidone was found to have two competitive reactions, namely the auto‐catalytic and the catalytic reactions. The apparent rate constants of each reaction were determined. Comparison of apparent rate constants between the model compound and the polymer reaction system are also reported.