bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steric hindrance in the amine–epoxide reaction
Authors: Glover Donald J. , Duffy James V. , Hartmann Bruce 
Published: April 2003

AbstractThe effect of steric hindrance on the reaction of silicon‐containing aliphatic amines with phenylglycidyl ether (PGE) has been studied using 13C‐NMR, a technique described by Sojka and Moniz [J. Appl. Polym. Sci., 20, 1977 (1976)]. It was found that steric hindrance produced a large change in the reaction rate of the primary and secondary amine hydrogens, thus leading to a separation of the polymerization and cross‐linking reactions.
Radical reactivity of α‐trifluoromethylstyrene
Authors: Ueda Mitsuru , Ito Hiroshi 
Published: April 2003

Abstractα‐Trifluoromethylstyrene (TFMST) does not undergo radical homopolymerization with azobis(isobutyronitrile) (AIBN) in bulk at 60°C. Low‐temperature initiation was not effective either. Radical copolymerization of TFMST (M2) with styrene (ST, M1) has yielded monomer reactivity ratios as follows: r1 = 0.60 and r2 = 0.00. It has been found that the cyclohexyl radical generated by reaction of cyclohexylmercuric chloride with sodium borohydride adds to the β‐carbon of TFMST 7.5 times faster than that of ST. Combination of the copolymerization analysis and the “mercury method” has allowed us to estimate Alfrey–Price Q and e parameters for TFMST to be 0.43 and 0.90, respectively. Thus, due to the strongly electron‐withdrawing effect of the trifluoromethyl group, this styrene is highly electron deficient. In spite of the favorable electronic effect, however, the ceiling temperature appears very low, presumably due to the steric hindrance.
Reactions and polymerization of 1‐trityl‐4‐vinylimidazole
Authors: Schiavone R. J. , Overberger C. G. 
Published: April 2003

Abstract1‐Trityl‐4‐vinylimidazole was prepared by direct tritylation of 4(5)‐vinylimidazole and polymerized using a free radical initiator. Poly(1‐trityl‐4‐vinylimidazole) was hydrolyzed using aqueous acetic acid to give poly[4(5)‐vinylimidazole]. The poly[4(5)‐vinylimidazole], which was obtained from the hydrolysis of poly(1‐trityl‐4‐vinylimidazole), was compared with poly[4(5)‐vinylimidazole] prepared directly from 4(5)‐vinylimidazole for differences in stereochemistry. The stereochemistry of both polymers was found to be similar by high‐resolution NMR. Thus, the trityl does not influence the stereochemistry of poly[4(5)‐vinylimidazole]. The reaction of 1‐trityl‐4‐vinylimidazole with n‐butyllithium gave 2‐lithio‐1‐trityl‐4‐vinylimidazole. This intermediate was used to prepare 2‐substituted 4(5)‐vinylimidazoles, which are new monomers that can be polymerized using free radical initiators.
Laser desorption/fourier transform mass spectra of poly(phenylene sulfide), polyaniline, poly(vinyl phenol), polypyrene, and related oligomers: Evidence for carbon clusters and feasibility of physical dimension measurement
Authors: Brown Charles Eric , Kovacic Peter , Welch Kenneth J. , Cody Robert B. , Hein R. E. , Kinsinger James A. 
Published: April 2003

AbstractLaser desorption/Fourier transform mass spectra of poly(phenylene sulfide), polyaniline, poly(vinyl phenol), polypyrene, poly(p‐phenylene), poly(1‐methyl‐2,5‐pyrrolylene), poly(1‐phenyl‐2,5‐pyrrolylene), and poly(2,5‐thienylene) are compared. Poly(phenylene sulfide) fragments at CS bonds during analysis, but rearrangement is minor. Evidence is found for dibenzothiophene moieties within the polymer chains. Unambiguous determination of the structure of polyaniline is not possible. Rearrangement appears to accompany chain scission. Completely aromatic polymers do not undergo similar reactions during analysis. Species with more carbons than can be accounted for by an integer multiple of six‐membered rings arise from side reactions during dehydrocoupling of aromatic monomers. Carbon clusters, which are observed in the spectra of some aromatic polymers, appear to arise from laser volatilization and multiphoton ionization of large polynuclear components that are formed during synthesis. Negative ions of about 40–120 carbons and positive ions with about 120–400 atoms are detected. The results also suggest that the physical dimensions of some polymer molecules might be measured by Fourier transform mass spectrometry.
Synthesis of poly(1,3,4‐oxadiazole)s by direct polycondensation of dicarboxylic acids with hydrazine sulfate using phosphorus pentoxide/methanesulfonic acid as condensing agent and solvent
Authors: Ueda Mitsuru , Sugita Hiroya 
Published: April 2003

AbstractA convenient method for the synthesis of poly(1,3,4‐oxadiazole)s of high molecular weights has been developed. These polymers were prepared readily by the direct polycondensation of dicarboxylic acids with hydrazine sulfate (1) using phosphorus pentoxide/methanesulfonic acid (PPMA) as both a condensing agent and solvent. Polycondensation of aliphatic dicarboxylic acids with 1 proceeded even at room temperature and produced poly(1,3,4‐oxadiazole)s with inherent viscosities up to 1.4 dL/g. The synthesis of aromatic poly(1,3,4‐oxadiazole)s from aromatic dicarboxylic acids containing phenyl ether structures was carried out by a one‐pot procedure because the preactivation of dicarboxylic acids was required. The synthesis of 2,5‐disubstituted‐1,3,4‐oxadiazoles by the reaction of carboxylic acids with 1 in PPMA was studied to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(1,3,4‐oxadiazole)s showed 10% weight loss both in air and in nitrogen at 440–490°C.
Formation and reaction of polyenesulfonic acid. I. Reaction of polyethylene films with SO3
Authors: Ihata Jyoji 
Published: April 2003

AbstractThe surface of polyethylene (PE) film was sulfonated by reaction with gaseous SO3. The structure of the sulfonated PE films was determined on the basis of spectroscopic data such as IR, UV, and resonance Raman spectra. It was confirmed that a PE film and SO3 gave unsaturated sulfonic acids and that, as the reaction proceeded, the elimination of sulfurous acids took place to form sulfonic acids having highly conjugated CC unsaturated bonds.
Formation and reaction of polyenesulfonic acid. III. Preparation and photoreaction of 1,3,5‐hexatriene‐1,6‐disulfonic acid
Authors: Ihata Jyoji 
Published: April 2003

AbstractAs a model for the reaction between polyethylene films and gaseous SO3, n‐hexane was allowed to react with gaseous SO3 to give 1,3,5‐hexatriene‐1,6‐disulfonic acid (HTDS), which was isolated from the reaction products by column chromatography. Furthermore, it was found that an aqueous solution of HTDS‐Na was sensitive to UV, which eliminated one of the sulfonic acid groups by a radical mechanism. sulfonic acids having less than three conjugated double bonds were not sensitive to UV.
Synthetic study of aromatic polybenzoxazinone derived from methylene‐4,4′‐diaminodiphenyl‐3,3′‐dicarboxylic acid
Authors: Padma S. , Mahadevan V. , Srinivasan M. 
Published: April 2003

AbstractPolybenzoxazinones were prepared in two successive steps from methylene‐4,4′‐diaminodiphenyl‐3,3′‐dicarboxylic acid and azodicarbonyl chloride in 40–60% yield. These polymers were characterized by molecular weight and IR and NMR spectra. Their physical properties like solubility, viscosity, and thermal stability were also studied in detail.
Grafting onto carbon black by the reaction of reactive carbon black having masked isocyanate or acyl azide group with functional polymers
Authors: Tsubokawa Norio , Kobayashi Kazuhisa , Sone Yasuo 
Published: April 2003

AbstractAlthough isocyanate group (NCO) introduced onto carbon black surface was inactivated rapidly upon storage, it could be stabilized by masking the NCO group with active hydrogen compounds such as acetylacetone, diethyl malonate, and sodium hydrogensulfite. Upon heating these carbon blacks having masked NCO group at 150°C, the NCO group was regenerated on carbon black by the decomposition of the masked NCO group. On the other hand, acyl azide (CON3) group introduced onto carbon black was stable at below 20°C, but readily decomposed to NCO group by heating. By means of the reaction of NCO group on carbon black with functional polymers having hydroxyl, amino, and carboxyl group, these polymers were effectively grafted onto carbon black surface. When carbon black having CON3 group was used as reactive carbon black, the grafting ratio of diol‐type polyethylene glycol (Mn = 8.2 × 103), polyethyleneimine (Mn = 2.0 × 104), polyvinyl alcohol (Mn = 2.2 × 104), and bifunctional carboxyl‐terminated polystyrene (Mn = 1.1 × 105) was determined to be 29.7, 81.7, 32.2, and 50.4%, respectively. The number of grafted polymer chain decreases with an increase in molecular weight of the polymers, because the shielding effect of NCO group by grafted polymer chain is enhanced with an increase in molecular weight of the polymer.
Chemistry of epoxide–polycarbonate copolymer networks
Authors: Yu Yunzhao , Bell J. P. 
Published: April 2003

AbstractDiepoxides and in‐chain carbonate groups react readily in the presence of quarternary ammonium salts, although reaction is not observed without this catalyst. Two moles of epoxide react with each mole of carbonate. When diepoxides and polycarbonates are reacted, a three‐dimensional network of chains crosslinked with carbonate groups is produced; the crosslink density is controlled by adjusting the epoxy/carbonate ratio. Tertiary amines and alkoxides also catalyze the epoxy/carbonate reaction, but these have the undesirable attribute of promoting epoxy polymerization. The presence of oligocarbonates accelerates the epoxy–amine reaction.
Nonclassical urea oligomers. IX. Photo‐reducing nature of binuclear copper complexes of noncyclic pendant‐type urea oligomers
Authors: Araki Takeo , Kubo Yasuo , Hino Atsushi , Yasuda Yohko , Kamachi Mikiharu 
Published: April 2003

AbstractThe octameric oligomers of 1‐(N‐substituted‐carbamoyl)‐aziridine, i.e., N‐ureanized‐oligo‐ethylenimines, form Cu(II) complexes. When the N‐substituents are phenyl(1, 3), methyl(2), and p‐tolyl(4) groups, the main portions of the Cu(II)‐complexes are binuclear. The binuclear oligomer–Cu(II) complexes showed characteristic properties of photo‐reduction of Cu(II) species, giving rise to stable yellow Cu(I) species. The ease of photo reduction strongly depends on the oligomer structures, especially on the nature of the pendant‐urea groups, i.e., 4 > 1,3 > 2. In the series of aromatic type urea‐oligomers, highly stable photo‐radicals were observed in ESR. By using an optically active oligomer (3) the molecular requirements for these characteristic properties were investigated with circular dichroism and cyclic voltammometry. And one of the plausible structures was deduced as the model of binuclear Cu(II) sites surrounded by oligomeric environments.
Telechelic sulfate ionomers. I. Preparation and solution and thermal properties
Authors: Hegedus R. D. , Lenz R. W. 
Published: April 2003

AbstractNew telechelic ionomers with zinc and sodium sulfate salt terminal groups on hydrogenated polybutadiene (HPB) backbones (I) were prepared from hydroxyl‐terminated hydrogenated polybutadiene (HTHPB) of three different molecular weights (1350, 2100, and 3200 g/mol). Quantitative acid‐base titration, elemental analysis, and NMR spectroscopy were used to verify the structure, and further characterization included differential scanning calorimetry (DSC) and solution viscometry. The DSC results indicated that the ionomers are free of impurities within the limit of the resolution of the method. Glass transition temperatures determined by DSC indicated that the elevation in glass transition temperature by ionic crosslinking was most strongly dependent on the molecular weight of the backbone of the telechelic ionomer. The solution viscometry results showed that the sulfation reaction did not cause either covalent crosslinking or chain scission. Furthermore, the solubility characteristics of the sulfate‐terminated hydrogenated polybutadiene (STHPB) oligomers were shifted towards a preference for polar solvents by the presence of salt groups. The lower molecular weight ionomers of the series showed polyelectrolyte‐like extension at very dilute concentrations in polar solvents. The onset of polymer gelation in hexane was observed for the ionomers which had the highest molecular weight backbones.
Synthesis of functionalized linear poly(divinylbenzene). III. Synthesis of polymeric delocalized carbanion of poly(divinylbenzene) and its reactions
Authors: Aoshima Sadahito , Higashimura Toshinobu 
Published: April 2003

AbstractA polymeric delocalized carbanion of poly(divinylbenzene) [poly(DVB)] (2) was obtained by the proton abstraction with alkyllithium from the acidic methine moieties (HA) of linear poly(DVB) (1), which was prepared by the polymerization of DVB initiated by acetyl perchlorate. The formation of polyanion 2 was confirmed by UV–visible spectroscopy (λmax = 630 nm) and the reaction with methyl iodide to give methylated poly(DVB). Delocalized polyanion 2 reacted with various electrophilic reagents in THF at 60°C, to yield poly(DVB) derivatives having pendant trimethylsilyl, vinyl, vinyloxyl, hydroxyl, and carboxyl groups. Proton abstraction with base and subsequent reactions with electrophiles were also studied with the linear unsaturated dimer of styrene (1,3‐diphenyl‐1‐butene), as a model for poly(DVB) 1.
Chemical modification of polynorbornene. I. Sulfonation in dilute solution
Authors: Planche J. P. , Revillon A. , Guyot A. 
Published: April 2003

AbstractThe sulfonation of dilute solutions of polynorbornene (PN) in CCl4 has been carried out using SO3–triethylphosphate complexes of various stoichiometries dissolved in dichloroethane (DCE) or trifluoro‐trichloro‐ethane (TTE). This leads to an electrophilic substitution, with very few side reactions, yielding high sulfonation ratios (ca. 85%). The initial reaction is first order in both reactants (PN and SO3) and has an activation energy of 17.5 kJ mol−1. The reaction becomes diffusion‐controlled after ca. 30 min at room temperature due to the precipitation of the partially sulfonated polymer. The initial rate is almost independent of the isomeric structure (cis or trans) and the molecular weight of the polymer, as well as on the stoichiometry of the SO3–TEP complex; it is higher when TTE is used as solvent. The final sulfonation ratio is strongly dependent on the concentration of SO3 and seems to be controlled by the conditions of diffusion inside the precipitated solid.
Radiation‐induced copolymerization of hydrophilic monomers: Synthesis and thermal properties
Authors: Ramakrishna M. S. , Deshpande D. D. , Babu G. N. 
Published: April 2003

AbstractThe radiation‐induced bulk copolymerization of 2‐hydroxyethyl methacrylate (HEMA), 2‐hydroxypropyl methacrylate (HPMA), and N‐vinyl‐2‐pyrrolidone (NVP) with methacrylic acid (MAA) was studied by using 60Co γ‐radiation at a dose rate of 0.16 ± 0.02 M rads/h. The copolymer composition was estimated from the carboxylic acid content and the reactivity ratios were determined by Kelen–Tüdós. In all the systems MAA was found to be the most reactive. The copolymers were characterized by intrinsic viscosity measurements in dimethyl formamide (DMF) at 30 ± 0.1°C. The thermal behavior of the copolymers was evaluated.
The initiation of vinyl polymerization by tetrakis (trialkyl‐phosphite) nickel (o) derivatives
Authors: Hargreaves Keith 
Published: April 2003

AbstractThe study of the polymerization of vinyl monomers initiated by zero‐valent nickel phosphite derivatives in the presence of organic halides has been extended to tetrakis (triethylphosphite) nickel (o) and tetrakis (tri 2‐chloroethylphosphite) nickel (o). A kinetic study with methyl methacrylate and carbon tetrachloride shows that the polymerization proceeds by a free radical process and that the mechanism of initiation resembles that previously reported for the corresponding triphenylphosphite and carbonyl derivatives. The primary process which becomes rate determining at sufficiently high carbon tetrachloride concentration is the nonreversible SN1 scission of an alkylphosphite ligand. These alkylphosphite initiators are considerably more active than the corresponding carbonyl derivatives, but are less active than the corresponding triphenyl‐phosphite derivative. The difference in activities between the aryl and alkylphosphite derivatives has been accounted for by differences in steric over‐crowding of these molecules.
γ‐Irradiation of Nylon 6
Authors: Gupta Mool C. , Pandey Rajbahadur R. 
Published: April 2003

AbstractViscosity, Infra‐red, NMR spectral measurement technique, density measurement, and electrical conductivity were used to study the changes that occured during γ‐radiolysis of Nylon 6. It was observed that it undergoes chain scission and crosslinking, but chain scission predominates over crosslinking in air irradiation. From melting temperature, density measurement, and the use of the Flory equation the enthalpy of fusion of Nylon 6 is 11.86 and 13.84 kJ/mol in an inert atmosphere and in air irradiation, respectively. The indirect effective band gap decreases and electrical conductivity increases when Nylon 6 is irradiated with γ‐rays.
Synthesis, microstructure, and copolymerization studies of 2‐chloroethyl α‐chloroacrylate
Authors: Pathak Chandrashekhar P. , Patni Mahendra J. , Babu Gaddam N. 
Published: April 2003

AbstractPoly(2‐chloroethyl α‐chloroacrylate) was synthesized by radical initiation, and its microstructure was evaluated using carbon‐13 NMR. Methyl methacrylate (M1) and 2‐chloroethyl α‐chloroacrylate (M2) were copolymerized in toluene at 55°C using azobisisobutyronitrile as initiator. The reactivity ratios are 0.37 ± 0.28 and 1.21 ± 2.26, The thermal properties of these copolymers have also been reported.
Kinetics and mechanism of the benzoin isobutyl ether photoinitiated polymerization of styrene
Authors: Lipscomb N. Thornton , Tarshiani Yassin 
Published: April 2003

AbstractThe kinetics of the photopolymerization of styrene in bulk and in dilute systems in the presence of benzoin isobutyl ether as photoinitiator have been examined. The values of the intensity exponent, calculated at different temperatures or at different styrene concentrations, and the monomer exponent, calculated at various intensities, showed significant departure from those predicted by the ideal kinetic scheme, particularly at high intensity, at low temperature, or at low styrene concentrations. Low molecular weight polymer was the dominant product when high light intensity or low polymerization temperature was used. As the temperature was raised, however, or as the intensity was reduced, a high molecular weight polymer became progressively more important. Kinetic and molecular weight data suggest that at low temperature, high intensity, and/or at low monomer concentration, the benzoyl radical is the dominant initiating species; and the benzyl ether radical was consumed mainly in the termination step. At low intensity, high temperature and/or high monomer concentration, however, it appears that both benzoyl and benzyl ether radicals initiated polymerization.
XPS analysis of NH3 plasma‐treated polystyrene films utilizing gas phase chemical modification
Authors: Nakayama Youichi , Takahagi Takayuki , Soeda Fusami , Hatada Kenji , Nagaoka Shoji , Suzuki Jirou , Ishitani Akira 
Published: April 2003

AbstractGas phase chemical modification (GCM) is found to be more preferable as a pretreatment for the XPS surface analysis of polymer materials than the conventional liquid phase treatment because it can circumvent problems such as solvent contamination and swelling. We have tried the quantification of the surface composition successfully by estimating the yield of the reaction from model samples. GCM was then applied to correlate the surface composition of NH3 plasma‐treated polystyrene films with their cell‐affinity. The amount of primary‐amine and that of carboxylic acid were directly determined by GCM. Although the amount of primary‐amine, 15–20% of total nitrogen, did not depend on the treatment intensity, the total amine content for the treated samples increased with the plasma treatment intensity. The quantity of carboxylic acid generated was found to be very small. All treated samples had better cell‐affinity than the control. The sample N2 (of medium treatment) showed the best cell‐affinity. The most strongly treated sample N3, with larger amine content than N2, showed worse cell‐affinity because of the interference by the sputtered SiO2 on the surface.
Studies on some radical transfer reactions by entrapping the radicals as polymer end groups. II. Reactions of ȮH radicals with amino acids
Authors: Pramanick Dinabandhu , Sarkar Jyotish , Bhattacharyya Ramanath 
Published: April 2003

AbstractThe reaction of ȮH radicals with a number of aliphatic amino acids has been studied by entrapping the resultant radicals as end groups of poly(methyl methacrylate) that have been detected and estimated by the sensitive dye partition technique. The rate constants of the reaction (in mol−1 L S−1) of 7 amino acids at 25°C and at pH 1.00 have been determined as 8.33 × 108 for glycine, 2.56 × 109 for β‐alanine, 2.01 × 109 for β‐alanine, 3.99 × 109 for 4‐amino butyric acid, 7.56 × 109 for (1+) valine, 1.42 × 1010 for (1−) leucine, and 5.98 × 1010 for 6‐amino caproic acid. Glycine, α‐alanine, β‐alanine, and 4‐amino butyric acid produced radicals that underwent deamination and incorporated only carboxyl‐bearing end groups in the polymer. The other amino acids, leucine, valine, and 6‐amino caproic acid, produced at least two types of radicals, radicals that underwent deamination and those that remained intact, and incorporated in the polymer both carboxyl‐ and amine‐bearing end groups but in different amounts. The latter type of radicals were about 29% from 6‐amino caproic acid, 23% from leucine, and 18% from valine. The change of pH from 0.80 to 2.72 did not produce any significant change in the end group profile of the polymer obtained, indicating no appreciable change in the rate of the reaction of ȮH radicals with the simplest amino acid glycine in the pH range studied.
Synthesis, physical, and thermal properties of linear poly(dialkoxyphosphinyl‐s‐triazine)s
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractA novel class of linear poly(dialkoxyphosphinyl‐s‐triazine)s were prepared by interfacial or solution polycondensation reactions of various diamines such as ethylenediamine, hexamethy‐lenediamine or bis(4‐aminocyclohexyl)methane with 2‐dialkoxyphosphinyl‐4,6‐dichloro‐s‐triazines. The latter were synthesized by reacting cyanuric chloride with an equimolar amount of trialkyl phosphite. The phosphorous‐containing polymers were characterized by inherent viscosity measurements as well as by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. The thermal properties of polymers were investigated by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Pyrolysis of all polymers was exothermic. Polymers were stable up to 150–200°C both in nitrogen and air atmosphere. They afforded 16–42% char yield at 700°C under anaerobic conditions.