bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical copolymerization of 3‐tri‐n‐butylstannylstyrene with several vinyl monomers
Authors: Al‐Diab Salem S. S. , Suh Hwan‐Kyu , Mark James E. , Zimmer Hans 
Published: April 2003

AbstractThe free radical homopolymerization and copolymerization of 3‐tri‐n‐butylstannylstyrene (3‐BTS) with styrene (ST), ethyl acrylate (EA), methyl methacrylate (MMA), vinyl acetate (VA), and acrylonitrile (AN) were carried out using 2,2′‐azobisisobutyronitrile (AIBN) at 60°C. It was found that the yield of conversion to poly(3‐BTS) increased with the molar ratio of initiator to monomer as well as with polymerization time. The conversion at equilibrium after 50 h was about 40%. The compositions of copolymer samples were determined from elemental analyses. Monomer reactivity ratio and Q‐e values were calculated. The copolymers of 3‐BTS‐MMA and 3‐BTS‐AN were found to be alternating. The copolymers of 3‐BTS with MMA, EA and AN were not soluble in any of a large number of organic solvents tested. The insolubility is believed to be due to formation of intermolecular coordination among the tributylstannyl moiety and the carbonyl or cyano groups of the polymer. These copolymers, however, were “soluble” in trihaloacetic acid, but this solubility was due to a cleavage of the trialkyltin moiety from the phenyl groups. The glass temperatures, Tg, and melting temperatures Tm, of the various polymers were also studied.
Effect of fluorine substituents on the properties of nylon copolymers
Authors: Kiyotsukuri Tsuyoshi , Tsutsumi Naoto , Sandan Tadamasa , Nagata Minoru 
Published: April 2003

AbstractNylon 610/65F and nylon 610/65 copolymers were prepared by melt polycondensation from the diethylester of sebacic acid (10) and hexafluoroglutaric acid (5F) or glutaric acid (5) with hexamethylene diamine (6). Reduced specific viscosities of nylon 610/65F were lower than those of nylon 610/65. The crystallinity measured by WAXS and the melting point measured by DTA were depressed by the copolymerization. The melting point depression of nylon 610/65F was much larger than that of nylon 610/65. The thermal decomposition temperature measured by TG was also depressed significantly for nylon 610/65F. The residue at 600°C was increased by the fluorine substitution. The copolymers with higher fluorine content became flame retardant. The solubility was appreciably affected by the fluorine substitution. The contact angle for nylon 610/65F varied in a complicated manner with increasing 65F content and tended to be higher than the corresponding nylon 610/65.
Synthesis and properties of new polyimides containing flourinated alkoxy side chains
Authors: Ichino T. , Sasaki S. , Matsuura T. , Nishi S. 
Published: April 2003

AbstractA series of new polyimides containing fluorinated alkoxy side chains are prepared from novel fluorinated alkoxy diamines. The dieletric constant at 1 kHz in the fluorinated polyimides decreases from 3.3 to 2.6 as fluorine content increases. The refractive index also changes from 1.58 to 1.48, dependent on the fluorine content. In addition, the fluorinated polyimides exhibit lower water absorption than the reference polyimides prepared from m‐phenylenediamine.
Gel permeation chromatographic analysis of polyurethane prepolymer synthesis kinetics. I. The effect of catalyst
Authors: Thompson Corley M. , Taylor Sue G. , Mcgee William W. 
Published: April 2003

AbstractPolyurethane prepolymers are a complex mixture of oligomers. The proportion of the various species in this mixture determines the handling properties of the prepolymer as well as the physical properties of the final polyurethane. An analytical method has been developed that gives a clear and sensitive picture of both the reaction kinetics and the concentrations of the oligomeric species in the prepolymer mixture. The analytical method is applied to the polypropylene glycol/tolylene diisocyanate/catalyst system. The expected changes in reaction rates and in the formation of higher oligomers in the prepolymer were observed when catalyst was added at three different polyol molecular weights. An alternative equation for predicting the number average degree of polymerization is developed for the cases where reactant ratios are significantly less than one. An empirical equation is derived that permits expressing the reaction kinetic data in a linear plot. This equation is used to express the results of this work.
Studies of reactions with polymers. V. The reaction mechanism and resultant structure of PVA with PAN in DMSO without any catalyst
Authors: Hu Chun‐Min , Chiang Wen‐Yen 
Published: April 2003

AbstractThe reaction of polyacrylonitrile with poly(vinyl alcohol) in dimethyl sulfoxide without any catalyst was studied, and it showed that the adjacent nitrile groups on polyacrylonitrile could be linked up to form conjugated carbon‐nitrogen sequence by the presence of poly(vinyl alcohol). However, no such reaction occurred when poly(vinyl alcohol) was replaced by i‐propanol or poly(vinyl alcohol) graft copolymers. The structure of the resulting polymers were proposed by means of IR, UV, 1H, and 13C‐NMR spectroscopies. On the basis of the results, the effect of polymer feed and polymerization condition on this reaction were discussed. The compositions were determined by elemental analysis. The viscosity and thermal analysis of the products were also determined. At feed weight ratios of poly(vinyl alcohol) to polyacrylonitrile above one‐half, gels were obtained.
Preparation and characterization of wet poly(vinyl chloride)‐polypyrolle composite film
Authors: Uosaki Kohei , Okazaki Kentaro , Kita Hideaki 
Published: April 2003

AbstractWet poly(vinyl chloride) (wPVC) coated glassy carbon (GC) electrode was prepared by casting a DMF solution of poly(vinyl chloride) on glassy carbon and immersing it in methanol, and then in water. The wPVC coated GC (wPVC/GC) electrode showed electrochemical activity in aqueous solution; therefore, it was possible to obtain a wPVC/polypyrolle (PPy) composite by electropolymerization from aqueous solution of pyrolle (Py) into the wPVC matrix on the electrode. PPy segregated in wPVC matrix and the mechanical properties of PPy was improved by forming a composite without changing the electrochemical properties of PPy. The PPy/wPVC ratio can be controlled by controlling the concentration of PVC in DMF solution.
Emulsion polymerization of vinyl acetate initiated by potassium persulfate‐cyclohexanone sodium bisulfite redox pair system
Authors: Badran A. S. , Moustafa A. B. , Yehia A. A. , Shendy S. M. M. 
Published: April 2003

AbstractThe emulsion polymerization of vinyl acetate using potassium persulfate and cyclohexanone sodium bisulfite as redox pair initiation system was studied. The rate of polymerization, maximum conversion, and the number of polymer particles produced were found to change with redox initiator, monomer and emulsifier concentrations, and temperature variation. The rate of polymerization was found to be dependent on the initiator, the monomer, and the emulsifier concentrations to the 0.88, 0.22, and 0.20 powers, respectively. The K2S2O8–NaHSO3 redox system was found to decrease maximum conversion and doesn't form a stable emulsion. The apparent arrhenius activation energy (Ea) estimated for the polymerization system was 65.6 kJ/mol. The viscosity average molecular weights for some obtained poly(vinyl acetate) were determined.
Mechanistic studies of the electrochemical polymerization of pyrrole: Deuterium isotope effects and radical trapping studies
Authors: Lowen Stephen V. , Van Dyke John D. 
Published: April 2003

AbstractThe mechanism of the electrochemical polymerization of pyrrole and pyrrole‐d4 has been studied by an examination of the kinetic deuterium isotope effect. The kinetic rate constants of the reaction were measured by cyclic voltammetry, UV/visible specrophotometric analysis of polymer growth, and quantitative gas chromatographic analysis of monomer uptake. All three techniques demonstrated no primary isotope effect, from which it is concluded that proton loss or abstraction is not involved in the rate‐determining step of the polymerization. Furthermore no consistent secondary effect could be observed, suggesting that the rate‐determining step is free of hybridization changes or hyperconjugative effects in the transition state. A radical trap experiment revealed that polymer formation is completely inhibited by the presence of a radical trap and thus a reaction with the scavenger is more favorable than coupling with another radical cation or a neutral monomer molecule. Previously proposed mechanisms are examined and compared in light of the present study. Oxidative coupling is favored as the mechanism for electrochemical polymerization of pyrrole and related compounds. For this mechanism the rate‐limiting step must be either oxidation of monomer or radical cation coupling.
Synthesis of difunctional initiator via the Peterson reaction
Authors: Lee Day‐Chyuan , Chung T. C. 
Published: April 2003

AbstractThis paper presents an improved method to prepare divinylphenyl compounds which are a useful class of precursors in preparing difunctional organolithium initiators. In the past, most of the divinylphenyl compounds reported were prepared from reactions of phosphorus‐substituted carbanions with aldehydes and ketones (Wittig reaction). The phosphorus by‐product of the Witting reaction was difficult to be completely removed from the final products. In this paper, we apply the Peterson reaction (silane substituted carbanions) to the synthesis of divinylphenyl compounds. This reaction appears to be operationally simpler and cleaner than the Wittig reaction since the by‐product of silane is easily removed by silica Gel chromatography. The syn‐elimination of β‐hydroxylsilane is complete and clean under NaH condition with no detectable isomers in the final product. The reaction of the divinylphenyl compound with S‐butylithium forms a difunctional organolithium initiator which is used to prepare triblock copolymers with the desirable microstructure in each block.
Alternating copolymerization of 2,4‐dicyano‐but‐1‐ene and isoprene. II. Mechanism of copolymerization
Authors: Cowie J. M. G. , Cree S. H. , Ferguson R. 
Published: April 2003

AbstractA careful compositional analysis of copolymers formed during the reaction of 2,4‐dicyano‐but‐1‐ene with isoprene has shown that the products are highly alternating over a broad feed range. The mechanism of alternation has been explored using four models, the terminal, complex‐participation, penultimate, and restricted penultimate. Nonlinear least‐squares analysis of the data for each model, followed by a statistical test to gauge the improvement of data fitting by each compared with the terminal model has been carried out. The statistical analysis is based on calculating the probability that one model has been carried out. The statistical analysis is based on calculating the probability that one model is significantly better than another, from the incomplete β‐function. This indicates that the restricted penultimate model gives the best description of the data and that significant charge‐transfer complex participation can be discounted.
Preparation and polymerization of the two isomeric (chloromethyl)oxetanes
Authors: Wicks Douglas A. , Tirrell David A. 
Published: April 2003

Abstract2‐(Chloromethyl)oxetane was prepared in 8% overall yield from 2‐propen‐1‐ol by protection of the alcohol with dihydropyran, epoxidation, ring expansion with dimethylsulfoxonium methylide, acid deprotection, and chlorination with triphenylphosphine in CCl4. 3‐(Chloromethyl)oxetane was prepared in 22% overall yield by hydroboration‐oxidation of 3‐chloro‐2‐chloromethyl‐1‐propene followed by base‐catalyzed cyclization. Each of the oxetanes was converted to the corresponding elastomeric homopolymer by treatment with a triethylaluminum–acetylacetone–water mixture. Poly[2‐(chloromethyl)oxetane] was found to be similar to polyepichlorophydrin in reactivity toward benzoate ion, whereas poly[3‐(chloromethyl)oxetane] is more reactive by a factor of 2.
The synthesis and morphology of semi‐interpenetrating polymer networks based on polyurethane–polydimethylsiloxane system
Authors: Xiao H. , Ping Z. H. , Xie J. W. , Yu T. Y. 
Published: April 2003

AbstractA series of semi‐interpenetrating polymer networks (semi‐IPNs) based on polyurethane and polydimethylsiloxane were prepared. They are formed by crosslinking the polydimethylsiloxane prepolymer with 3‐aminopropyltriethoxysilane in the presence of linear polyurethane. Investigations were carried out by swelling measurement, dynamic mechanical analysis, Fourier transform infrared experiments, and scanning electron microscopy. It is concluded that the crosslinking of the polydimethylsiloxane network is restricted by the presence of the polyurethane, and the grafting level between the two components is low. The system is phase separated, and there is dual phase continuity in the midrange composition.
Polymerizable viscoelastic fluids
Authors: Peiffer D. G. 
Published: April 2003

AbstractRheological, elongational flow, and scanning electron microscopy measurements have been performed on cationic monomers associated with specific counterions. The monomers are formed through the reaction of allyl bromide and a variety of dimethylalkylamine derivatives. The results show that above a specific monomer–counterion concentration, highly elongated structures are formed in solution. These structures are adequately described as polymerizable rod‐like micelles. The physical properties of these fluids are interpreted in terms of a micellar sphere to rod transition which gradually occurs over a specific concentration range (>1g/dL, in general). At higher concentrations, these rod‐like entities are capable of interacting with each other. Therefore, even though the forces holding the structures together are certainly weaker than a chemical bond, polymeric‐like properties are observed in these polymerizable viscoelastic fluids.
Phase separation in polystyrene latex interpenetrating polymer networks
Authors: Sheu H. R. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractPolystyrene/polystyrene latex interpenetrating polymer networks (IPNs) were prepared by seeded emulsion polymerzation of styrene–divinylbenzene mixtures in crosslinked monodisperse polystyrene seed latexes. The resulting latexes comprised uniform nonspherical particles, which were formed by separation of the second‐stage monomer from the crosslinked seed network during swelling and polymerization. The kinetics of phase separation were investigated by examining the changes in particle morphology using optical microscopy, which revealed that the phase separation was induced by the relaxation of the polymer chains before polymerization began and was enhanced by increased conversion. The thermodynamics of phase separation were investigated by analysis of the free‐energy changes during swelling and polymerization, and the phase separation was described by a nucleation‐and‐growth mechanism. The results of this study have been applied to the design and synthesis of a series of uniform nonspherical particles of different morphology.
Uniform nonspherical latex particles as model interpenetrating polymer networks
Authors: Sheu H. R. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractPolystyrene/polystyrene latex interpenetrating polymer networks (IPNs) were prepared by seeded emulsion polymerization of styrene–divinylbenzene mixtures in crosslinked monodisperse polystyrene particles. The resulting latexes comprised uniform nonspherical particles, e.g., ellipsodal and egg‐like singlets, symmetry and asymmetric doublets, and ice cream cone‐like and popcorn‐like multiplets. The nonspherical particles, which were formed by separation of the second‐stage monomer from the crosslinked seed network during swelling and polymerization, are excellent models for studying phase separation in IPN's. The degree of phase separation increased with increasing degree of crosslinking of the seed particles, monomer/polymer swelling ratio, polymerization temperature, and seed particle size, and with decreasing divinylbenzene concentration in the swelling monomer. The results were consistent with a thermodynamic analysis based on the elastic‐retractile force of the polymer network, the monomer/polymer mixing force, and interfacial tension force.
Crosslinkable aromatic polyketones with maleimide pendent groups
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractA novel class of crosslinkable aromatic polyketones with maleimide pendent groups were synthesized by Friedel–Crafts polymerization from 5‐maleimido‐isophthaloylchloride and various aromatic reagents. The synthesized polyketones showed a poor solubility. They were characterized by inherent viscosity measurements and infrared (IR) spectroscopy. Differential thermal analysis (DTA) revealed that their crosslinking occurred at relatiively lower temperatures (167–253°C) than did thermal polymerization of ordinary bismaleimides. The thermal‐and thermooxidative stability of crosslinked resins were evaluated by dynamic thermogravimetric analysis (TGA) as well as by isothermal gravimetric analysis (IGA). They were stable in N2 up to 303–329°C and formed anaerobic char yield 50–62% at 800–C. The thermal stability of crosslinkable polyketones was significantly increased after curing.
Thermostable laminating resins based on aromatic diketone bis‐ and tetramaleimides
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractTwelve structurally different bis‐ and tetramaleimides were synthesized by Friedel–Crafts reaction between 4‐maleimido‐benzoylchloride or 3,5‐bismaleimido‐benzoylchloride and various aromatic reagents. They were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Crosslinked resins were obtained by curing the monomers at 250°C/6 h. Thermal characterization of monomers and cured resins was accomplished by differential thermal analysis (DTA), dynamic thermogravimetric analysis (TGA), and isothermal gravimetric analysis (IGA). Tetramaleimides were polymerized at lower temperatures than did the respective bismaleimides. The cured resins were stable up to 317–385°C in N2 atmosphere and formed an anaerobic char yield of 52–66% at 800°C.
Synthesis and mesogenic properties of four series of polyesters derived from dicarboxylic and dihydroxylic aromatic monomers
Authors: Barberá Joaquín , Navarro Fernando , Oriol Luis , Piñol Milagros , Serrano José Luis 
Published: April 2003

AbstractSome members of four series of polyesters were synthesized by the direct polycondensation of two types of dicarboxylic acids (4,4′‐dicarboxy‐α,ω‐diphenoxyalkanes and 4,4′‐dicarboxy‐α,ω‐dibenzoyloxyalkanes) with two types of bisphenols (4,4′‐dihydroxy‐α,ω‐diphenoxyalkanes and 4,4′‐dihydroxy‐α,ω‐dibenzoyloxyalkanes) using tosyl chloride in pyridine in the presence of N, N‐dimethylformamide. The 1H‐NMR spectra of the polymers synthesized showed that these polymers have an ordenated structure. The mesogenic properties of these polymers were studied by optical microscopy and differential scanning calorimetry. Many of the polymers show nematic mesomorphism.
Liposome formation of selectively‐polymerized diene‐containing phospholipids and their postpolymerization
Authors: Takeoka Shinji , Ohno Hiroyuki , Iwai Hidetaka , Tsuchida Eishun 
Published: April 2003

AbstractSmall and large unilamellar liposomes composed of 1,2‐bis(2,4‐octadecadienoyl)‐sn‐glycero‐3‐phosphorylcholine (DODPC) are prepared by sonication and extrusion, respectively. They are polymerized with water‐insoluble radical initiator, azobis(isobutyronitrile) (AIBN) which can selectively polymerize diene groups in 1‐acyl chains of the lipids. Polymerized liposomes are freeze‐dried to obtain the polymerized liposome powder. There are two methods to redisperse lyophilized liposomes into water. The extrusion is an effective method to disperse them because the energy at extrusion is necessary only for redispersion, whereas the excess energy at sonication gives damage on liposome structure. There is no difference in stability between polymerized liposomes before and after redispersion with extrusion. DODPC polymers, obtained from free radical‐initiated polymerization with AIBN, are linear and have polymerizable diene groups in 2‐acyl chains. The liposome powder is therefore soluble in organic solvents. Reconstruction of polymerized liposomes is performed with lipid polymers having low or high molecular weight. The lipid polymers having high molecular weight provide stable large unilamellar liposomes by ethanol injection, but unstable small unilamellar liposomes are formed by sonication. The liposomes reconstructed from lipid polymers having low molecular weight are unstable regardless of their size. After reconstruction of liposomes selectively polymerized by AIBN, diene groups in 2‐acyl chains are polymerized by water‐soluble radical initiator or UV‐irradiation to yield highly crosslinked structure. Their stability is improved remarkably by this postpolymerization.
The effect of masked isocyanates on the moisture absorption of MY 720/DDS epoxy resin
Authors: Lonikar S. V. , Rungsimuntakul N. , Gilbert R. D. , Fornes R. E. 
Published: April 2003

AbstractSeveral masked isocyanates were prepared with variations in both the type of isocyanate and masking group. They were characterized by elemental analysis and NMR spectroscopy, and their unblocking temperatures were determined. In general, higher unblocking temperatures were obtained using acyclic and cyclic aliphatic isocyanates and fluorinated phenols. Those with unblocking temperatures in the range of 120–180°C were incorporated into MY 720/DDS epoxy resin prior to cure. Highly fluorinated variations were incompatible with the resin. IR and DSC analyses showed that residual functional groups in the epoxy resin reacted with the masked isocyanates. Reductions in moisture absorption as high as 65% were obtained depending on the masked isocyanate. DMA studies showed that the Tg of the epoxy resin is lowered by incorporation of the masked isocyanate but the elastic modulus (E′) is relatively unchanged at temperatures below Tg.
Miniemulsion copolymerization of vinyl acetate and butyl acrylate. IV. Kinetics of the copolymerization
Authors: Delgado Joaquin , El‐Aasser Mohamed S. , Silebi Cesar A. , Vanderhoff J. W. 
Published: April 2003

AbstractThe copolymerization kinetics of conventional emulsions and miniemulsions of 50:50 and 25:75 molar ratios vinyl acetate–butyl acrylate monomer mixtures were studied using sodium hexadecyl sulfate as surfactant. Hexadecane was the cosurfactant used in the preparation of the miniemulsions, and ammonium persulfate was the initiator used in the polymerizations. The rate of polymerization showed four regions which extended to different conversions depending on the type of emulsion used (conventional or miniemulsion). The rate of polymerization for the miniemulsion process was always slower than for the conventional process. The dependence of the rate on the initiator concentration was higher for the miniemulsion process. The number of particles nucleated in the miniemulsion copolymerization process was lower than in the conventional emulsion copolymerization process. The initiator and surfactant concentration dependence of the number of particles were 0.8 and 0.25 for the miniemulsion copolymerization process and 0.0 and 0.68 for the conventional emulsion copolymerization process respectively. These effects were attributed to the different particle nucleation mechanism operating in each process.