bluuebunny/crossref_metadata_2025_split huggingface dataset:
A reassessment of the 1H‐NMR spectra of styrene/methyl methacrylate copolymers
Authors: Uebel J. J. , Dinan F. J. 
Published: April 2003

AbstractThe methoxy 1H‐NMR assignments in the 2.1–3.7δ region for styrene/methyl methacrylate copolymers have been assessed in terms of pentad sensitivity. Several of the methoxy resonances suggested by this study differ from literature assignments. The evidence in support of these reasignments is based on a comparison of calculated and observed triad distributions and on the good agreement of the value of the reactivity ratio rM calculated from individual triads with that obtained by classical methods. A new procedure for the determination of the tacticity coefficient σ is applied.
The use of acrylic acid‐co‐nylon substrates for immobilizing enzymes
Authors: Abdel‐Hay F. I. , Beddows C. G. , Gil M. H. , Guthrie J. T. 
Published: April 2003

AbstractA number of poly(acrylic acid)‐co‐nylon graft copolymers were prepared. Two approaches were used. The first involved the direct, radiation‐induced grafting of acrylic acid onto the nylon, while the second involved the hydrolysis of polyacrylonitrile‐co‐nylon graft copolymers. All the resulting poly(acrylic acid)‐co‐nylon graft copolymers coupled large amounts of protein when the carbodimides CMC and EDAC were used as coupling agents. However, when the enzymes β‐galactosidase and trypsin were immobilized, the retention of activity was relatively low. A number of reasons for this effect can be postulated, some of which were investigated. From the evidence, it would appear that the major reason is that the carboxylic acid groups are fixed to a “rigid” backbone, which allows them to interact with the enzyme after the establishment of an initial covalent attachment. Additionally, with acid phosphatase, it was observed that the enzyme interacted with immobilized carboxylic acid groups before coupling occurred.
Ziegler–Natta polymerization of butadiene: Kinetic and molecular weight study
Authors: Honig J. A. J. , Burford R. P. , Chaplin R. P. 
Published: April 2003

AbstractThe effect of reaction conditions on conversion and molecular weight in the polymerization of butadiene initiated by cobalt octoate/diethylaluminum chloride/water was studied. The polymerization exhibited complex kinetics with respect to cobalt concentration. The molecular weight, as a function of conversion, was investigated. Chain transfer to aluminum alkyl was of only minor importance.
Liquid crystal polymers. 14. Synthesis and properties of thermotropic poly(1,4‐alkylphenylene terephthalates)
Authors: Dicke Hans‐Rudolf , Lenz Robert W. 
Published: April 2003

AbstractA series of terephthalate polyesters was prepared from substituted hydroquinone monomers that contained a single cyclic or branched alkyl group. All the polymers were crystalline with melting points well below 400°C that decreased as the size of the cycloalkyl substituent increased. Most of the polymers had clearing temperatures below 400°C and all formed nematic melts. Copolyesters that contained equimolar amounts of two different substituted hydroquinone monomers, which were crystalline and had broad temperature ranges for nematic phase formation, were also prepared.
Synthesis of polyester by direct polycondensation with triphenylphosphine
Authors: Yasuda Satoshi , Wu Guo‐Chuang , Tanaka Hozumi , Sanui Kohei , Ogata Naoya 
Published: April 2003

AbstractDirect polycondensation reactions of various dicarboxylic acids and diols were carried out at room temperature with triphenylphosphine and polyhalo compounds to obtain polyesters in good yield. Reaction conditions including solvent, temperature, concentration of monomer, amount of reagents, and effect of matrix on direct polycondenation were investigated. A combination of triphenylphosphine and hexachloroethane was found to be satisfactory for the polyester synthesis. The addition of matrix polymers such as poly(4‐vinylpyridine) in the reaction system enhanced the direct polycondensation reaction, and a polyester with a solution viscosity of 2.24 was obtained from bisphenol A and isophthalic acid under the optimum condition.
Etude par RMN 13C à 62,89 MHz des branchements éthyles dans les copolymères ethylène‐butène et polyéthylène basse densité
Authors: Grenier‐Loustalot Marie‐Florence 
Published: April 2003

AbstractCarbon 13 nuclear magnetic resonance spectra (at 62,89 MHz) were obtained for a series of branched heavy alcanes (12‐ethyl tricosane, 11,20‐diethyl tricontane, 11,18‐diethyl octacosane, 11,17‐diethyl heptacosane, 11,16‐diethyl hexacosane, 9,12‐diethyl heneicosane, 5,7‐diethyl docosane, 6,7‐diethyl docosane, 2 éthyl‐hexyl‐12 tricosane), which provide a model set for describing the ethyl branched sequences in ethylene butene copolymers and low‐density polyethylene (LDPE). For ethylene‐butene copolymers we do not detect any head‐to‐head polymerization of butene as reported recently (the existence of a 1,2‐ethyl pair has not been confirmed by the low‐field signal at 41,3 ppm), but only isolated ethyl and 1‐3‐diethyl branches. The three peaks observed in the methyl region (broad signal) of the spectrum are assigned to butene centered triads, as opposed to branches in positions having different tacticities as reported earlier. Carbon 13 nuclear magnetic resonance spectra of high‐pressure polymerized low‐density polyethylene have been measured at 62,89 MHz. On the basis of Willbourn's double back biting mechanism, two kinds of complex branches, the 1,3‐ethyl pair and 2‐ethyl‐hexyl, have been assigned. Finally, these results suggest that the ethyl branches in low‐density polyethylene are not isolated branches.
Etude par RMN 13C à 62,89 MHz de ramifications longues d'alcanes lourds branchés. Modèles de PEbd et des copolymères éthylène‐α oléfines
Authors: Freche Patrick , Grenier‐Loustalot Marie‐Florence 
Published: April 2003

AbstractA series of 12‐alkyl tricosanes (four compounds) was examined by use of 13C nuclear magnetic resonance at 62,89 MHz as model compounds for isolated short‐ and long‐chain (C5, C6, C7, C8) branches in low‐density polyethylene and ethylene‐α olefin copolymers. An array of 13C resonances was observed and we note that the 13C chemical shifts became insensitive to branch length with octyl and longer branches at this field.
Photocycloaddition of cis‐cyclooctene to low‐molecular‐weight polystyrene and some aromatic model compounds
Authors: Beckewitz F. , Heusinger H. 
Published: April 2003

AbstractThe product formation of 1,3 cycloaddition of cis‐cyclooctene to a low‐molecular‐weight polystyrene as well as to some monoaromatic and diaromatic model compounds is investigated. Information on the structure of the products mainly with respect to the number of phenyl rings attacked within the molecules is obtained by mass spectrometry.
Morphology and grafting in polybutylacrylate‐polystyrene core‐shell emulsion polymerization
Authors: Min T. I. , Klein A. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractThe morphology of polybutylacrylate–polystyrene (PBA–PS) core‐shell latex particles prepared by seeded emulsion polymerization was investigated as a function of the addition method of styrene (St). The thin layer chromatography/flame ionization detector (TLC–FID) technique was used to characterize the morphology of the core‐shell latexes. It was found that grafting PS to the PBA core occurs during seeded emulsion polymerization. The percentage of grafting depended on the method of addition of St, being greatest for the batch reaction, less for the preswollen batch reaction, and least for the semibatch reaction. Upon aging the PBA core‐polymer migrated out of the latex particles with a low degree of grafting to form dumbellshaped particles, whereas the PBA–PS core‐shell particles with a high degree of grafting remained spherical because of the emulsifying ability of graft copolymer.
Vinyl polymerization. 416. Polymerization of vinyl monomer initiated by polyethyleneglycol
Authors: Ouchi Tatsuro , Hosaka Yoshifumi , Beika Nobuaki , Imoto Minoru 
Published: April 2003

AbstractThe polymerization of vinyl monomer initiated by polyethyleneglycol (PEG) in aqueous solution was carried out at 85°C with shaking. Acrylonitrile (AN), methyl methacrylate (MMA), and methacrylic acid were polymerized by PEG–300 (M̄n = 300), whereas styrene was not. The effects of the amounts of monomer and PEG, the molecular weight of PEG, and the hydrophobic group at the end of PEG molecule on the polymerization were studied. The selectivity of vinyl monomer and the effect of the hydrophobic group are discussed according to “the concept of hard and soft hydrophobic areas and monomers.” The kinetics of the polymerization was investigated. The overall activation energy in the polymerization of AN was estimated as 37.9 kJ mol−1. The polymerization was effected by a radical mechanism.
Plasma polymerization. IX. A systematic investigation of materials synthesized in inductively coupled plasmas excited in perfluoropyridine
Authors: Clark D. T. , Abu‐Shbak M. M. 
Published: April 2003

AbstractThe RF plasma polymerization of perfluoropyridine was investigated for a range of operating parameters. The stoichiometries of the resulting thin films indicated a predominance of rearrangement mechanisms in their formation in which both nitrogen and fluorine were retained at approximately the same level as in the starting monomer. In appropriate cases a comparison was drawn with plasma polymers produced under comparable conditions from perfluoro and pentafluorobenzenes. Although the plasma polymer films from the benzenes have a low critical surface tension, that for the pyridine system changes with time, and the surface becomes completely wettable with water. This is attributed to surface hydrolysis of the plasma polymer films produced from perfluoropyridine.
The analysis of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO® resin) in mixtures of PPO resin, polystyrene, and copolymers of PPO resin and polystyrene
Authors: White D. M. , Hallgren J. E. 
Published: April 2003

AbstractA method of determining the quantity of ungrafted poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO®Trademark of General Electric Company.
resin) in mixtures of such polyphenylene oxide or PPO resin, polystyrene (PS), and graft copolymers of PPO resin and PS is described. The technique is a combination of physical and chemical separations and gel permeation chromatographic (GPC) analysis. The extent of grafting on PPO resin and the quantity of ungrafted PPO resin were calculated from molecular weight data and compositional analysis.
Free‐radical copolymerizations of N‐arylmaleimides. II
Authors: Patel J. D. , Patel M. R. 
Published: April 2003

AbstractFree‐radical copolymerization of methyl acrylate (MA) with N‐p‐chlorophenylmaleimide (NPCMI) and N‐p‐bromophenylmaleimide (NPBMI) initiated by AIBN in cyclohexanone solution at 75°C was studied. The copolymer composition has been determined from the nitrogen content and NMR spectra of the copolymers. The reactivity ratios have been calculated by ML, FR, KT, and JJ methods. Q and e values of NPCMI and NPBMI have also been calculated by the Alfrey–Price Q‐e scheme.
Novel high‐temperature‐resistant metal phthalocyanine imide copolymers
Authors: Achar B. N. , Fohlen G. M. , Parker J. A. 
Published: April 2003

AbstractNew metal phthalocyanine imide copolymers with high thermal stability, based on the reaction between metal (11) 4,4′,4″,4‴‐phthalocyaninetetraamine, 4‐aminophenylether, and 1,2,4,5‐benzenetetracarboxylic dianhydride, were prepared. Infrared (IR) spectra, thermogravimetric analysis (TGA), and viscosity measurements were used to characterize these polymers. All polymers exhibited good thermal and thermooxidative stability at polymer decomposition temperatures (PDT) greater than 500°C in air and nitrogen atmosphere. Another attractive feature is their high char yields—60–75% at 800°C in nitrogen atmosphere. The ratio of the polymer decomposition temperatures in air and nitrogen atmospheres, (PDTair)/(PDT), varied from 0.94 to 0.98. These polymers have promising applications in heat‐stable films, fibers, and coatings.
Solid‐state polymerization studies of conjugated diacetylenes deca‐2,8‐diene‐4,6‐diyne‐1,10‐diol and derivatives
Authors: Khandelwal P. K. , Talwar S. S. 
Published: April 2003

AbstractThe title diacetylenic compound (D3) and its derivatives dibenzoate (D3B), dinitrobenzoate (D3mNB), ditosylate (D3PTS), and diurethane (D3PU) were synthesized and their solid‐state reactivity examined under irradiation and thermal stimulation. D3, D3B, and D3PTS crystallized in reactive phases. The thermal and irradiation polymerization behavior of D3 and D3B was examined further by time‐conversion curves.
Effects of ionizing radiation on linear aromatic polyesters
Authors: Bell Vernon L. , Pezdirtz George F. 
Published: April 2003

AbstractThe influence of chemical structure on the response of aromatic polyesters to high‐energy ionizing radiation was studied. Systematic variations of polymers related to poly(ethylene terephthalate) were subjected to γ radiation, and the competitive chain scission and crosslinking reactions were determined by measuring changes in intrinsic viscosity and molecular weights. It was found that an increase in the paraffinic glycol segment of polyterephthalates facilitated crosslinking, while the protective nature of aromatic groups was demonstrated by modifying the dibasic acid segments. The influence of substituents on the terephthalate moiety was mixed: electronegative groups led to chain scission (as evidenced by decreased viscosities), but electropositive substituents exerted a stabilizing effect on polymer viscosity. In almost all cases, number‐average molecular weights were decreased by exposure to γ radiation, regardless of viscosity behavior. Crystalline melting temperatures of the polymers generally were decreased by the combined radiation effects of chain scission and crosslinking.
Structure of chlorinated poly(vinyl chloride). XII. Configuration and reactivity of low‐molecular‐weight models of poly(vinyl chloride) in the course of chlorination
Authors: Lukáš R. , Jakeš J. , Palečková V. , Pokorny S. , Kolínský M. 
Published: April 2003

AbstractThe chlorination of poly(vinyl chloride) (PVC) was investigated by means of low‐molecular‐weight models of PVC—a dimer and trimer of PVC, viz., 2,4‐dichloropentane (2,4‐DCP) and 2,4,6‐trichloroheptane (2,4,67‐TCH). Chlorinations of stereoisomeric mixtures of 2,4‐DCP and 2,4,6‐TCH have revealed that the d,1 form of 2,4‐DCP (syndio‐2,4‐DCP) is more reactive in the chlorination than the meso form of 2,4‐DCP (iso‐2,4‐DCP), while in the case of the chlorination of 2,4,6‐TCH the reactivity of stereoisomers decreases in the order iso‐> hetero‐>syndio‐2,4,6‐TCH; consequently, analogous structures of stereoisomers of 2,4‐DCP and 2,4,6‐TCH react in a reverse order and not in the same one. The qualitative order of reactivities of stereoisomers may be correlated formally with the magnitude of their dipole moments. The reactivity of stereoisomers of 2,4‐DCP and 2,4,6‐TCH decreases with increasing dipole moment.
Thermoswitching property in TCNQ salts of ionenes containing poly(ethylene oxide) segments
Authors: Takizawa Yoshio , Aiga Hirotsugu , Watanabe Masayoshi , Shinohara Isao 
Published: April 2003

AbstractIonene polymers characterized by the alternating structure of ionene and crystalline poly(ethylene oxide) (PEO) segments were prepared as a function of PEO segment size. A microstructure of these ionenes and their 7,7,8,8‐tetracyanoquinodimethane (TCNQ) salts were investigated with x‐ray diffraction patterns, thermal scanning behavior, and polarizing micrographs. On the basis of this microstructure, the change in resistivity with temperature was studied. In Arrhenius' plots of the resistivity the simple salts in which the spherulites consisting of the PEO segments were observed showed a sharp decrease in resistivity with a rise in temperature [critical temperature resistor (CTR)] at about the melting point of the PEO segments, whereas the other simple salts in which the spherulites were not observed showed linear temperature dependence. The switching properties were confirmed similarly in repetitive heating/cooling cycles. This CTR characteristic was attributed to an increase in continuity in the conduction paths by melting spherulites. The apparent switching properties were not observed in the complex salts.
Bis‐, tris‐, and tetrakis‐maleimidophenoxy‐triphenoxycyclotriphosphazene resins for fire‐ and heat‐resistant applications
Authors: Kumar Devendra , Fohlen George M. , Parker John A. 
Published: April 2003

AbstractNovel fire‐ and heat‐resistant polymers was obtained by the thermal polymerization of various maleimidophenoxy‐triphenoxycyclotriphosphazenes. These polymers, in which the cyclic triphosphazene structure is preserved, have thermal stability to 350°C and char yields of 82–78% at 800°C in nitrogen and 78–71% at 700°C in air. Two groups of monomers were synthesized by reacting tris(4‐aminophenoxy)‐tris(phenoxy)cyclotriphosphazene with maleic anhydride alone or in combination with benzophenonetetracarboxylic or pyromellitic dianhydride. The structures of cyclic phosphazene‐trimeric precursors and the polymers were characterized by Fourier‐transform infrared, proton nuclear magnetic resonance, and elemental analysis. The thermal stabilities of the polymers were evaluated by thermogravimetric analysis.
Head‐to‐head vinyl polymers. X. Cyclopolymerization of o‐dimethacryloyloxybenzene
Authors: Ohya Takahiro , Otsu Takayuki 
Published: April 2003

AbstractTo clarify the possibility of preparing a polymer that contained head‐to‐head (h–h) methyl methacrylate (MMA) unit radical cyclopolymerization of o‐dimethacryloyloxybenzene (o‐DMB) was investigated. p‐Dimethacryloyloxybenzene (p‐DMB) was also used in comparison. When the polymerizations were carried out with higher monomer concentrations than ca. 0.5 mol/L, benzene‐insoluble polymer was produced. The extent of cyclization (fc) in benzene‐soluble polymer increased with a decrease in the monomer concentration and an increase in the polymerization temperature. The 1H‐NMR and 13C‐NMR spectra of poly(MMA) derived from poly(o‐DMB) by hydrolysis and methylation were in fairly good agreement with those of ordinary head‐to‐tail (h–t) poly(MMA). Therefore, it was concluded that the intramolecular propagation in cyclopolymerization of o‐DMB was mainly performed by a h–t mechanism. However, the initial and maximum degradation temperatures of the poly(MMA) were observed to be somewhat higher than those of the ordinary poly(MMA), which suggests that a minor amount of the h–h unit was formed.
Glow discharge polymerization in the mixture of tetramethylsilane and ammonia gas
Authors: Inagaki N. , Nejigaki K. , Suzuki K. 
Published: April 2003

AbstractColorless, transparent, and filmy polymers prepared from mixtures of tetramethylsilane (TMS) and ammonia gas (NH3) were investigated by elemental analysis, infrared (IR) spectroscopy, and ESCA. These polymers contained a large amount of nitrogen residues in the form of amine, amide, and amine oxide groups. Their concentration varied with the composition of the starting TMS/NH3 mixtures. The mixing of NH3 gas with TMS influenced the chemical state of Si residues and accelerated the oxidation of Si atoms to form silicon oxides such as SiO, Si2O3, and SiO2. The polymers formed by glow discharge polymerization in the TMS/NH3 mixtures were combinations of Si‐ and N‐containing polymers and silicon oxides.
Reactive oligomers. I. Preparation and polymerization of ethylene glycol bis(methyl fumarate)
Authors: Matsumoto Akira , Jiang Guang‐Jie , Oiwa Masayoshi 
Published: April 2003

AbstractEthylene glycol bis(methyl fumarate) (EGBMF) was prepared as a new type of divinyl compound and reactive oligomer: a needle crystal, m.p. 104.5°C. Homopolymerization of EGBMF was carried out in dioxane with 0.1 mol/L AIBN at [M] = 1 mol/L and 60°C; the rate of polymerization was estimated to be 4.44 × 10−6 mol/L s in a good agreement with diethyl fumarate (DEF). The cyclization constant Kc was obtained as 1.64 mol/L, being rather low compared with diallyl oxalate which is 1,9‐diene having two ester groups analogous to EGBMF. Gelatin occurred at about 35% conversion. Finally, the copolymerization of EGBMF (M1) with diallyl phthalate (DAP) (M2) is tentatively explored with the intention of the improvement of allyl resins in mechanical properties; remarkable rate enhancement was observed for copolymerization. The monomer reactivity ratios were estimated to be r1 = 0.96 and r2 = 0.025, the r1 value being reduced compared with the DEF‐DAP copolymerization system. These results are discussed from the standpoint of steric effect on the polymerization of fumarate as an internal olefin.
Ignition of low‐density polyethylene slabs by a small flame
Authors: Clark Ferrers R. S. 
Published: April 2003

AbstractSlabs of low‐density polyethylene (LDPE) were exposed to the wake of a lean hydrogen‐oxygen flat flame. The ignition delay and initial flame velocity after the ignition were measured at several gas‐air equivalence ratios and distances from the igniting flame. When ignition occurred, the surface temperature was far lower than that required for pyrolysis in the absence of oxygen. Small amounts of char formed on the polymer surface during the delay, consistent with the involvement of oxygen in solid‐phase preignition processes. Plots of In(delay) versus 1/(absolute temperature) were linear and the activation energy was derived from the Arrhenius equation, 64 ± 10 kJ/mol. Initial rates of flame development decreased with increased separation between the polymer and the igniting flame, but unlike those reported for poly(methyl methacrylate), they were independent of the duration of the preceding delay except when the polymer was very close to the flame. The results are explained by a model in which both the ignition delay and the subsequent rate of flame development depend on the concentration of species associated with the chain‐propagation steps of the combustion process.
Thermal stability of poly(vinyl bromide) and vinyl bromide‐methyl acrylate copolymers. I
Authors: Diab M. A. 
Published: April 2003

AbstractThe thermal stability of PVB and five VB‐MA copolymers with different compositions was studied by thermogravimetric analysis in dynamic nitrogen. The reactivity ratios of the copolymers were determined by using NMR techniques. It was found that r1(VB) = 0.5 ± 0.1 and r2(MA) = 7.3 ± 0.3. The stability of VB increases as the MA concentration in the copolymer compositions increases. Apparently, the formation of lactone and anhydride structures has a stabilizing effect. The stability imparted to the degrading copolymers by lactone and anhydride structures is insufficient to produce stability comparable to that of PMA itself.
Radiation‐induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. II. Studies on bromine labeling
Authors: Bhattacharyya S. N. , Maldas D. 
Published: April 2003

AbstractFormation of the active sites on irradiated trunk polymer, for example, cellulose acetate, was determined by taking recourse to bromine labeling and the G values of active sites were accordingly evaluated. The G value was as well determined through analysis of peroxide. It has been concluded that the G value measured by bromine labeling corresponds to accessible radicals, while that evaluated through measurement of peroxide accounts for the total. The number‐average molecular weights of the graft chains were calculated and these were found to be dependent on monomer composition.