摘要:

AbstractThe kinetics of the emulsifier‐free emulsion copolymerization of styrene and sodium styrene sulfonate have been examined over a range of comonomer compositions. The rate of polymerization was found to increase dramatically in the presence of small amounts of sodium styrene sulfonate. This increase is attributed to the increased number of particles formed when sodium styrene sulfonate was present and to a gel effect enhanced by ion association. At low concentrations of functional comonomer, where a monodisperse product was obtained, a homogeneous nucleation mechanism of particle generation is proposed. At higher concentrations, broader and then bimodal size distributions were obtained, and this is ascribed to significant aqueous phase polymerization of sodium styrene sulfonate. The water‐soluble homopolymer is supposed to act as a locus of polymerization. The occurrence of this aqueous phase side reaction and the generation of secondary particles makes impossible the preparation of highly sulfonated polystyrene latexes by batch or seeded batch emulsion copolymerizat

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300201

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractSolid‐state13C NMR spectroscopy has been used to determine the decrease in CC bonds, formation of crosslinks and cis to trans isomerization during the γ irradiation of (a)>99%cis, 1,4‐polybutadiene, (b) 54%trans, 41%cis, 1,4‐polybutadiene, and (c) 86% 1,2‐polybutadiene.G(‐cisCC) andG(‐transCC), were similar and decreased with dose from ≈ 40 for 0‐1 MGy to 5 for 5‐10 MGy.G(‐double bonds) andG(crosslink) were comparable, indicating that crosslinking occurred through the double bonds.G(crosslink) was much higher than values derived from physical properties, confirming that NMR measures the total of inter‐ and intramolecular crosslinking (cyclization). The 1,2 polybutadiene was much more sensitive to crosslinking, and a value ofG(‐CC) = 240 was obtained at low doses. Crosslinking evidently proceeds by a kinetic chain reaction in

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300202

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel two‐step method for the synthesis of polybenzothiazoles has been developed starting from 2,5‐bis(isoprophylthio)‐1,4‐phenylenediamine and aromatic dicarboxylic acid chlorides. The low‐temperature solution polycondensation of these monomer pairs inN‐methyl‐2‐pyrrolidone afforded the aromatic polyamides with pendant isopropylthio groups having inherent viscosities in the range of 0.8 and 2.4 dL/g. The soluble precursor polyamides were subjected to thermal cyclization to the corresponding polybenzothiazoles along with the elimination of propylene and water. The resulting polymers were als

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300203

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel betaine internal salt (3) has been synthesized by the reaction of pyridine with 1‐methyl‐2‐bromo‐4,5‐dicyanoimidazole (1). The reaction of pyridine with1serves as a model for the reaction of poly(4‐vinylpyridine) with1. The reaction of poly(4‐vinylpyridine) with1gives betaine salt substituted polymers which were characterized by IR, NMR, UV‐visible spectroscopy, and viscometry. The substituted polymers were compared to the model compound (3) and to unsubstituted poly(4‐vinylpyridine) in order to determine polymer structure and the degree of substitution. One of the substituted polymers shows polyelectrolyte behavior. Thermal characterization of the substituted polymers shows two exothermic transitions at 260 and 340°C attributed to chemical reactions of

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300204

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel AB‐type block copolymer composed of dextran and polyamide sequences was prepared through the following two approaches. One is a coupling reaction of a terminal functional group introduced in the dextran chain with that in the polyamide chain, such as the reaction of an amine group with an acyllactam group or that of a lactone group with an amine group at the corresponding chain ends. The other is an anionic polymerization of a bicyclic lactam activated with a trimethylsilylated dextran derivative having an acyllactam end group. The latter procedure was found to be more effective for the preparation of the block copolymer having a high molecular weight polyamide sequenc

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300205

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe preparation of poly(4‐oxy‐1,4‐phenylenesulfonyl‐4,4′‐biphenylene‐4‐sulfonylphenylene) (PBP) has been accomplished by the base mediated, polycondensation reaction between two biphenyl containing monomers. The bisphenol, 4,4′‐bis[(4‐hydroxyphenyl) sulfonyl]biphenyl (HSB), was reacted with 4,4′‐bis[(4‐chlorophenyl)sulfonyl]‐biphenyl (CSB) in tetramethylene sulfone solvent. The highest mechanical properties and glass transition temperature was observed for polymer PBP with a reduced viscosity around 1.0 dL/g. Consequently, the current synthesis route provides polymer with higher properties than other historical preparative routes. Blends of PBP with a different poly(ether sulfone) were miscible based on the observance of a single glass transition temperature. TheTgs of the polymer blends exhibited an unusual positive deviation from the weighted line

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300206

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel addition polymerization of 1,4‐benzenediselenol (BDSe) to 1,4‐diethynylbenzene (DEB) was carried out by UV‐irradiation in toluene at 60°C under nitrogen atmosphere. The polymerization proceeded at such a fast rate as to give 60–70% yield for 6 min. A paleyellowish polymer (M̄n= 20000–30000) precipitated with the progress of the polymerization. In the presence of BPO, the polymerization also proceeded rapidly to give the polymer (M̄n= 18000) in 50% yield for 4 min. The polymerwas insoluble in conventional organic solvents. In the IR spectrum of the polymer, the characteristic absorption bands ofcis‐ andtrans‐vinylene groups appeared at 1340 and 940 cm−1, respectively. The microstructures of polymers were evaluated as the cis content was 90% and the trans one was 10%, based on the model adducts of benzeneselenol and ethynylbenzene. The cis ← trans isomerization occurred with UV‐irradiation: thecisvinylene group of the polymer decreased from 90 to 40% for 18 h. The electrical conductivity of the polymer was in the order of 10−13S/cm without dopant, but increased up to 10−5S/cm on I2doping. DSC and TG thermograms of the polymer indicated its decomposition point as 465°

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300207

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractMonodisperse porous polymer particles in the size range of 10 μm in diameter were prepared via seeded emulsion polymerization. Linear polymer (polystyrene seed) or a mixture of linear polymer and solvent or nonsolvent were used as inert diluents. The pore diameters of these porous polymer particles were on the order of 1000 Å with pore volumes up to 0.9 mL/g and specific surface areas up to 200 m2/g. The physical features of the porous polymer particles depended on the diluent type and the crosslinker content, as well as the molecular weight of polymer seed particles. By varying the molecular weight of the linear polymer, monodisperse porous polymer particles with different pore size distribution could be synthesized. Polymer seed with a low degree of crosslinking instead of linear polymer could also be used to prepare monodisperse porous polymer particles with smaller pore volume and pore siz

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300208

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractMonodisperse porous styrene‐divinylbenzene copolymer particles were prepared via seeded emulsion polymerization using a mixture of linear polymer (polystyrene seed) and non‐solvent as inert diluent. Experimental evidence was presented to describe the mechanism of formation of porous polymer particles during the copolymerization and solvent extraction stages, in which porosity was a consequence of phase separation in the presence of diluents. Pore structure formation was investigated by changes in copolymerization kinetics, gel content, crosslinking density, particle morphology, surface area, pore volume, and pore size distribution. The process of copolymerization was presented, based on the concepts of production, agglomeration, and fixation of the interior gel microspheres of polymer particles. A portion of linear polymer used as diluent was found to participate in the network structure while the porous matrix was built‐up. The influence of the removal of the linear polymer from the matrix pores during the solvent extraction process on the porous structure was also disc

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300209

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractPhotoreductions of polymer‐bound anthraquinone in degassed water‐ and 2‐propanolswollen 2‐hydroxyethyl methacrylate hydrogel films were performed at 313 and 334 nm, and in sunlight for the water‐swollen system. The quantum yield at 334 nm for production of anthrahydroquinone was 0.31 in water and 0.94 in 2‐propanol. Results at 313 nm were very similar. A reversible oxygen insensitive side product, indentified as 10‐hydroxyanthrone, was produced simultaneously to the anthrahydroquinone in water‐swollen films, but not for 2‐propanol. A small amount of irreversible side product, believed to be hydroxylated anthraquinone, was also formed in the water system. A photochemical reaction scheme is suggested to account for these observations. Hydrogen peroxide production from photoreduction‐reoxidation cycling of the hy

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300210

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY