bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and microstructure of polymers from o‐methacryloyloxybenzoic acid
Authors: San Román J. , Madruga E. L. , Pargada L. 
Published: April 2003

AbstractThe free radical polymerization of o‐methacryloyloxybenzoic acid using acetone and benzene as solvents, in the interval 30–120°C, is investigated. The polymerization in benzene has a precipitant character. However, when acetone is used as solvent, at reaction temperatures higher than 60–70°C, the polymerization deviates from the classic free radical mechanism and, beside the addition of monomer molecules to growing chain ends, the release of salicylic acid and the formation of cyclic anhydride structures of glutaric type in the main chain has been detected. The microstructure of polymers obtained has also been studied by the transformation into the corresponding poly(methyl methacrylate)s.
Spectroscopic studies of photochemical reactions in organic solids: Photopolymerization of 1,4 bis[β‐pyridyl(2)vinyl] benzene
Authors: Ghosh Urmi , Chattopadhyaya S. , Misra T. N. 
Published: April 2003

AbstractThe laser Raman phonon spectroscopic technique has been used to study the photopolymerization reaction of 1,4 bis[β‐pyridyl(2)vinyl] benzene (P2VB). Raman and infrared spectroscopy have been used to study the intramolecular vibrations of the reactant and the product and to characterize them. Absence of any large Stokes' shift between absorption and emission bands of the monomer crystal shows that exciton–phonon coupling is weak, and the reaction is not likely to be phonon mediated. Phonon spectroscopy shows that the reaction proceeds by a heterogeneous mechanism. Sharp phonon bands of the product, however, suggests that the photopoly P2VB lattice is highly ordered.
Soapless emulsion polymerization of methyl methacrylate in water in the presence of barium sulfate
Authors: Konno Mikio , Shimizu Koichi , Arai Kunio , Saito Shozaburo 
Published: April 2003

AbstractTo investigate the kinetics of soapless emulsion polymerization in the presence of a solid phase, polymerization experiments were carried out for the methyl methacrylateK2S2O8H2O system using barium sulfate powder, which is assumed to be chemically inert. Reaction conditions were varied with respect to the ranges of initiator concentration, monomer concentration, agitation speed, and quantity of powder. Experimental results showed that the polymerization rate is greatly affected by the addition of powder. It is concluded that the physical circumstances of the polymerization are changed considerably with the addition of the powder. A conceptual model for the mechanism of the polymerization was proposed to explain the effects of the experimental variables.
Thermotropic polyesters with main chain isomeric naphthylene, trans‐1,4‐cyclohexylene, and 2,5‐pyridinediyl units: The importance of the order of ester linkages in the mesogenic units
Authors: Jin Jung‐Il , Choi E‐Joon , Ryu Seog‐Chul 
Published: April 2003

AbstractTwo new series of thermotropic polyesters were prepared and their mesomorphic properties were investigated. The polymers consist of triad aromatic ester‐type mesogenic units with decamethylene spacers. The mesogenic units of the first series are composed of isomeric dihydroxynaphthalene moieties as the central structure flanked by two p‐oxybenzoyl groups. In the second series the mesogenic units were of reversed ester linkages: the central moieties, derived from 1,4‐naphthalene dicarboxylic acid, trans‐1,4‐cyclohexanedicarboxylic acid, or 2,5‐pyridinedicarboxylic acid, are connected on both sides to p‐phenylene structures. Two low molecular weight model compounds with 1,4‐naphthylene unit at the center of the mesogenic unit were synthesized and their mesomorphic properties were compared with those of corresponding polymers. It was observed both for the model compounds and the polymers containing 1,4‐naphthylene units that the linking order of the ester group in the mesogenic unit exerted a decisive influence on the capability for the formation of a mesophase. Thermal and mesomorphic properties were investigated by DSC, on a polarizing microscope equipped with a hot‐stage, and by visual observation of stir‐opalescence of the melts.
Polyelectrolyte effects on the quenching of pyrene fluorescence in solutions of a pyrene substituted poly(acrylic acid)
Authors: Arora Kartar S. , Turro N. J. 
Published: April 2003

AbstractThe quenching of pyrene fluorescence by nitromethane, Tl+, Cu2+, I−, and 4‐dimethylaminopyridine (DMAP) in aqueous solutions of a pyrene substituted poly(acrylic acid) (1) was influenced by the “polyelectrolyte effect” of 1. The efficiency of quenching in solutions of 1 was measured in terms of the Stern–Volmer constants for dynamic and static quenching which were obtained from comparison of the intensity and lifetime of pyrene fluorescence in solutions of 1 and a monomer model compound. The efficiency of quenching in solutions of 1 was always greater at high pH (9) in comparison to that at low pH (4). The ionization of carboxylic groups in 1 caused an expansion of the polymer mainchain and concomitant exposure of the pyrene molecules to the aqueous phase and quencher. The polyanion domain of 1 favored the condensation of cationic quenchers and could account for very efficient quenching in case of Cu2+ and Tl+. A very efficient quenching of pyrene fluorescence in solutions of 1 by DMAP at high pH was attributed to the hydrophobic interactions of DMAP and pyrene moiety. The iodide ions were less efficient quenchers of pyrene fluorescence due to electrostatic repulsion from the polyanion. The efficiency of quenching by nitromethane was not significantly affected by ionization of the carboxylic groups in 1.
Electronic properties of the linear ladder polymer, poly[4‐(3‐pyridyl),8‐methyl,2,3–6,7‐quinolino] (PPMQ)
Authors: Ruan J. Z. , Litt M. H. 
Published: April 2003

AbstractElectronic paramagnetic resonance (EPR) and conductivity of pristine and iodine‐doped PPMQ were studied. The pristine polymer EPR signal exhibited a Lorentzian line shape. Unpaired spin density measurements indicated that the spin concentrations of the undoped polymer lie in the range of one spin per 150–190 repeat units at room temperature. The peak‐to‐peak width doubled, the line shape became asymmetric and the spin concentration in the polymer increased slightly after doping with iodine. EPR saturation experiments show that the spin lattice relaxation time T1 is sensitive to trace impurity. Considerable reduction of T1 after doping with iodine shows strong coupling between the spin system and N‐iodonium nucleus. Conductivity increases up to 5 orders of magnitude by iodine doping; at room temperature, the best value found was 0.017 S/cm. The activation energy for conductance after doping is about half that of pristine polymer.
Alternating copolymerization of β‐methylstyrene and maleic anhydride
Authors: Vuković R. , Kurešević V. , Fleš D. 
Published: April 2003

AbstractAlternating copolymers of β‐methylstyrene and maleic anhydride were prepared by free‐radical‐initiated polymerization in bulk and in toluene as a solvent. The reactivity ratios k1c/k12 and k2c/k21 were calculated from the change of copolymerization rate with a monomer feed at a constant total monomer concentration according to the generalized model of Shirota and coworkers. From the equation Rp = Rp(f) + Rp(CT) were calculated Rp(f) and Rp(CT), and it was found that in toluene the copolymerization proceeds predominantly by the addition of CT‐complex monomers. Termination occurs predominantly by homotermination of β‐methyl‐styrene macro free radicals, kt22, but the cross termination kt21 is also operative.
High resolution 13C‐NMR spectroscopy of sodium carboxy methyl cellulose
Authors: Chaudhari S. N. K. , Gounden K. C. , Srinivasan G. , Ekkundi Vadiraj S. 
Published: April 2003

AbstractResults of NMR studies on intact sodium carboxy methyl cellulose (SCMC) are presented. Similar studies in the literature are all on partially depolymerized SCMC. The degree of substitution and the relative distribution of substituents at OH‐2, OH‐3, and OH‐6 of anhydro D‐glucose residue in intact SCMC were determined by high resolution 13C‐NMR spectroscopy (125 MHz). It is observed that the degree of substitution at OH‐6 is almost equal to that at OH‐3. In two SCMC samples, which are widely different in molecular weight and degree of substitution (ds), the relative reactivity order of the hydroxyl groups was found to be OH‐2 > OH‐6 ≃ OH‐3. The NMR assignments were based on calculated shifts of carbons of anhydroglucose moiety in an oligosaccharide due to substitution.
Grafting of optically active nucleic acid base derivatives onto poly(vinylamine) as polynucleotide analogs
Authors: Overberger C. G. , Chen C. C. 
Published: April 2003

AbstractPolynucleotide analogs consisting of poly(vinylamine) as the backbone and optically active thymine and adenine derivatives as the pendants were synthesized. The pendants were prepared by the addition reaction of the nucleic acid base to ethyl crotonate followed by hydrolysis. The pendants were resolved using brucine as the resolving agent and an acetone‐water mixture as the fractional crystallization solvent. The active esters of the pendants also were prepared. Poly(vinylamine) was isolated from water employing a weak acid, N‐hydroxysuccinimide (HOSu), to protect the amino group of the poly(vinylamine). Model reactions for grafting were examined. Grafting reactions were carried out by reacting the active esters with the PVAm.6HOSu complex at room temperature.
On the photoreactivity of diacetylene containing thermoplastic block copolymers
Authors: Liang Rong‐Chang , Reiser Arnost 
Published: April 2003

AbstractA group of block copolymers containing diacetylenes as chain extenders in their hard segments was prepared, based on urethanes, esters, ureas, and amides as hard segments and polybutadienes, polyethers, polyesters, and polysiloxanes as soft segments. Almost all block copolymers were photoreactive, but there was a wide range of sensitivities. The photoreactivity of the copolymers was found to depend on the reactivity of the monomer unit, on the width of the diacetylene stacks in the hard segments, and on the degree of phase separation in the solid films.To explore the range of monomer reactivities we prepared 15 crystalline monomers. Urethanes were in general the most reactive, and this was attributed in part to the specific effect of hydrogen bonding which brings about a shortening of the C1 to C4 distance between diacetylenes tend to reduce the photoreactivity.The behavior of identical diacetylene units in the monomer crystal, in the homopolymer, and in the block copolymer is discussed in this paper.
Conformational properties of isotactic poly(2‐hyroxyethyl methacrylate) in the mixed water‐alcohol solvents
Authors: Kim Whan Gun , Jeon Sang Il , Jhon Mu Shik 
Published: April 2003

AbstractConformational properties of isotactic poly(2‐hydroxyethyl methacrylate) (PHEMA) have been studied in mixtures of water and several aliphatic alcohols by viscometry and fluorometry. The highest fluorescence intensity of auramine has been detected in aqueous isotactic PHEMA solution compared with several aliphatic alcohol systems. Upon aliphatic alcohol addition, there was the decrease of fluorescence intensity of auramine. As the number of aliphatic group of alcohol increases, the decrease of fluorescence intensity of auramine has been pronounced. And the sharp increases of the reduced viscosity of isotactic PHEMA in water‐alcohol solvents were observed in the lower region of alcohol volume percentage with the increasing number of aliphatic group of alcohol. Nevertheless, the sharp increase of the reduced viscosity of isotactic PHEMA in ethyleneglycol‐water solvent was obtained even at a low‐volume percentage region of ethyleneglycol at which compact structures exist. Therefore, we consider that the increase of viscosity at this region is due to the hydrophilic side group of polymer‐solvent interaction, forming hydrogen bonds. The experimental results suggest that compact structures of isotactic PHEMA in aqueous solution are caused by hydrophobic interactions by methyl group of polymer backbone, and the hydrophobic interaction by adding alcohols. Finally, our study brings the fact that the solvating sites of alcohols on the isotactic PHEMA molecule are strongly influenced by the number of hydroxyl and aliphatic group in alcohols.
Thermal decomposition processes in aliphatic polysulfides investigated by mass spectrometry
Authors: Montaudo G. , Scamporrino E. , Puglisi C. , Vitalini D. 
Published: April 2003

AbstractThe thermal degradation of four aliphatic polysulfides (polythiomethylene, polythiotrimethylene, polythioethylene, and polythiohexamethylene) was investigated by direct pyrolysis in the ion soruce of a mass spectrometer (DPMS) operating both in electron impact (E.I.) and chemical ionization (C. I.) modes. Flash‐pyrolysis GCMS was also used in the case of polythiomethylene(polysulfide I) to confirm the DPMS results. The overall evidence indicates that the primary thermal decomposition of these polymers yields cyclic sulfides by an intramolecular exchange process. A β‐CH hydrogen transfer reaction, occurring in parallel with the former process, produces primary pyrolysis compounds with SH end‐groups.
Kinetics of polyesterification III: Solid‐state polymerization of polyethylene terephthalate
Authors: Chen Show‐An , Chen Fu‐Lung 
Published: April 2003

AbstractExperimental studies on the solid‐state polymerization (SSP) of polyethylene terephthalate (PET) for the particle sizes of 14–16 mesh at 170–200°C and for the particle sizes of 14–18 mesh at 210–240°C are carried out under a vacuum of about 60 mtorr. Analysis of the data of the concentrations of hydroxyl and carboxyl groups and the number average molecular weight during the SSP allows determinations of the rates of esterification and ester interchange separately. It is found that at the temperature 170–200°C and the particle size 80–100 mesh the SSP is end‐group diffusion limiting, and that at the temperature 210–240°C and the particle size 14–16 mesh the ester interchange is ethylene glycol diffusion limiting and the esterification is predominantely end‐group diffusion limiting due to higher diffusion rate of water. These phenomena are explored by an assistance of the proposed rate expressions for the end‐group diffusion limited reactions and diffusion models for the by‐products, water, and ethylene glycol.
Liquid crystal polymers. VIII. Liquid crystalline polyesters of trans‐4,4′‐stilbenedicarboxylic acid and 1,3‐propanediol
Authors: Jackson W. J. , Morris J. C. 
Published: April 2003

AbstractIn our recent overview of liquid crystalline polyesters of trans‐4,4′‐stilbenedicarboxylic acid (SDA) and aliphatic glycols,1 we reported that “… the 1,3‐propanediol polyester did not exhibit thermotropic liquid crystallinity (no stir opalescence or DSC endotherm above Tm), perhaps because of the relatively high Tm (303°C) for a polymer of a glycol having an odd number of carbon atoms.” We now have studied the melting characteristics of another sample of this polymer more carefully and have concluded that it does exhibit a liquid crystalline mesophase over a very narrow temperature range. In this Note we give the thermal properties of this polymer and the thermal and mechanical properties of an SDA/1,3‐propanediol copolyester which we also injection molded. These properties are compared and contrasted with those of the similar polyester and copolyester prepared with 1,4‐butanediol instead of 1,3‐propanediol.
Isotopic effects in H‐atom abstraction from matrix molecules by methyl radicals in poly(methyl methacrylate). Determination of the scale of relative reagent motions
Authors: Bagryansky V. A. , Tolkatchev V. A. 
Published: April 2003

AbstractThe H‐abstraction by ĊH3 and ĊD3 radicals from PMMA molecules is investigated at 77 and 120 K. The film samples are prepared from the mixture of normal and deuterated PMMA. The reaction is of the first order with respect to radical concentration. Its rate is retarded in time as compared to the exponential law. An analysis of the molecular product ratio for the reaction allows the primary isotopic effect to be estimated. The initial reaction rate depends nonmonotonously on the proportion of the deuterated polymer in the matrix. Namely, there exists a range of isotopic compositions, with the reaction rate increasing with the portion of a deuteropolymer in the mixture. At 77 K the reaction rate of ĊD3 is lower than that of ĊH3 in PMMA of a mixed isotopic composition. This results from the proximity of ĊD3 with unreactive parental macromolecules, which reduces the local H concentrations around ĊD3 as compared to the mean concentration. At 120 K the radical decay rates do not differ. This fact cannot be explained by unfrozen mobilities of radicals at high temperatures or by their migration from parental macromolecules. The phenomenon is interpreted in terms of thermal fluctuations involving a great area around a radical and ensuring its migration within this area. The electron spin echo method is used to estimate the distance between a radical and its parental macromolecule, a ≥ 9.6 Å. This is the lower limit of the reaction accessibility.
Graft copolymerization of methyl methacrylate onto wool initiated by ceric ammonium nitrate–thioglycolic acid redox couple in presence of air. IV
Authors: Shukla J. S. , Sharma G. K. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate (MMA) onto wool initiated by ceric ammonium nitrate (CAN)–thioglycolic acid (TGA) redox couple has been studied at 55 ± 0.2°C under atmospheric oxygen. Grafted copolymer was characterized by IR spectroscopy, scanning electron micrographs, and thermogravimetric analysis. Effect of amines, acid, alkali, oxidizing, and reducing agents were determined experimentally. The molecular weights of grafted poly(methyl methacrylate) and homopolymer was also evaluated.
Polymerization in nonuniform latex particles: Distribution of free radicals
Authors: Chern Chorng‐Shyan , Poehlein Gary W. 
Published: April 2003

AbstractPrevious kinetic studies in emulsion polymerization have almost always involved an assumption of uniform distribution of free radicals in the latex particle. Such an assumption is not likely to reflect reality in many systems that employ water‐soluble initiators because the hydrophilic end‐group of the oligomeric free radical will preferentially stay in the surface layer of the particle. This constrained end‐group location would result in nonuniform distribution of free radicals in the polymerizing latex particles. A Monte Carlo simulation of the growth of a single polymer chain within the latex particle supports this hypothesis. Such a nonuniform distribution of free radicals in the latex particle is expected to have an influence on reaction kinetics and product properties. The mechanism for transport of free radicals out of polymerizing latex particles is reexamined based on the proposed concept, and a modified expression for the desorption rate constant is presented.
Kinetic and ESR studies on the radical polymerization of Di‐n‐butyl itaconate in benzene
Authors: Sato Tsuneyuki , Inui Shukei , Tanaka Hitoshi , Ota Tadatoshi , Kamachi Mikiharu , Tanaka Kohji 
Published: April 2003

AbstractThe polymerization of di‐n‐butyl itaconate (DBI) intiated with AIBN was kinetically investigated in benezene. The polymerization rate (Rp) was expressed by: Rp = k[AIBN]0.5[DBI]1.7. The polymerization showed a considerably low overall activation energy of 15.3 kcal/mol. The initiator efficiency of AIBN in this system decreased with increasing DBI concentration, ranging from 0.34 to 0.55°C, which is ascribable to viscosity effect due to the monomer. From an ESR study, the polymerization system was found to involve two kinds of persistent radicals, namely, primary propagating (III) and propagating (I) radicals. The relative concentration of III to I increased with decreasing monomer concentration. Azo‐nitrile initiators such as AVN and ACN similarly produced two persistent radicals, while MAIB, DBPO, and PBO yielded only propagating radical I as persistent. The MAIB‐initiated polymerization of DBI was also performed in benzene. Similar kinetic features were observed, that is, a higher dependence of Rp on the DBI concentration and a low overall activation energy (14.4 kcal/mol). The following rate equation was obtained at 50°C:Rp = k[MAIB]0.5[DBI]1.6. The initiator efficiency of MAIB decreased with increasing DBI concentration, ranging from 0.32 to 0.53 at 50°C. The concentration of propagating radical I was determined by ESR at 50 and 61°C, from which kp and kt were estimated. The kp value increased with increasing monomer concentration, while the kt one decreased with the DBI concentration. These values are much lower compared with those of MMA.
Ethylene–propylene copolymerization initiated with solubilized Ziegler–Natta macromolecular complexes. I. Determination of kinetic parameters
Authors: Cansell François , Siove Alain , Fontanille Michel 
Published: April 2003

AbstractCopolymerization of ethylene with propylene (E–P) was initiated with soluble polystyrene –butadiene–Li/TiCl4 complexes in toluene leading to vinylic‐olefinic based block copolymers. The activity of the system was measured at a constant ratio r = Li/Ti for different feed compositions. From measurements of the amount of copolymers produced, a direct determination of the efficiency of the catalytic system was made. This efficiency was found to be close to that obtained for homopolymerizations of C2H4 and C3H6 initiated with the same catalytic complex (≃ 80% with respect to the concentration of “carbon‐titanium” bonds).Both the measured values of the efficiency and the determination of the molar masses of the polyolefinic block are consistent with a living character of the system involved in the E–P copolymerization. In such conditions well‐defined linear [styrene]‐b‐[ethylene‐co‐propylene] copolymers were obtained. Furthermore, 13C NMR analyses allowed determination of the comonomer reactivity ratios, the values of which indicate an E–P random copolymerization.From both these values and those of the absolute rate constants of propagation determined for the homopolymerization of C2H4 and C3H6 initiated with the same catalytic system, the absolute rate constants of cross‐propagation were deduced.
Photopolymerization initiated by charge–transfer complex. X. Photopolymerization of methyl methacrylate with the use of isoquinoline–sulphur dioxide charge–transfer complex
Authors: Lenka Subasini , Nayak Padma L. , Nayak Sanjay K. 
Published: April 2003

AbstractAqueous polymerization of methyl methacrylate in visible light was studied using isoquinoline–sulphur dioxide (IQ–SO2) charge–transfer complex as the photoinitiator. Analysis of kinetic and other data indicate that the polymerization proceed via a radical mechanism and the termination is dependent on the initiator concentration. Chain–termination via degradative chain (initiator) transfer appears to be predominant here.
Alternating copolymerization of maleic anhydride with allyl chloroacetate
Authors: Mamedova S. G. , Rasulov N. Sh. , Rzaev Z. M. 
Published: April 2003

AbstractSome regularities of radical alternating copolymerization of maleic anhydride with allyl chloroacetate are studied. The formation of donor–acceptor complexes between comonomers with complexing constant Kc = 0.052 L/mol is found using 1H NMR spectroscopy. The kinetic parameters for this copolymerization reaction are found and the quantitative contribution of monomer complexes to chain‐growth radical reactions is calculated. It is shown that either a “free‐monomer” mechanism (dilute solutions) or a “mixed” mechanism (concentrated solutions) prevails for chain growth during radical copolymerization depending on total monomer concentration. It is found that inhibition of degradative chain transfer in the course of the reaction studied takes place owing to the presence of α‐chlorine atom in the allyl chloracetate molecule and formation of charge transfer complex.