The anionic polymerization of octamethylcyclotetrasiloxane （D4） catalyzed by tetramethyl ammonium hydroxide （TMAH） in the presence of water under the conditions of high temperature and oxygen-off was investigated....The anionic polymerization of octamethylcyclotetrasiloxane （D4） catalyzed by tetramethyl ammonium hydroxide （TMAH） in the presence of water under the conditions of high temperature and oxygen-off was investigated. The conversion of polymerization and the molecular mass of the polymer were examined by Gel Permeation Chromatography （GPC）. Based on mechanism analysis,the calculation model of terminated hydroxy concentration （ c OH ） was obtained. And the result of the increase of c OH with conversion was observed by using the model. Then the influence of reaction conditions on the change of the value of c OH with conversion was investigated.The increase of the hydroxy terminated rate was greater than that of the polymerization rate with increasing temperature.The increase of the polymerization rate was greater than that of the hydroxy terminated rate with the concentration of catalyst increasing. With the concentration of water increasing,the polymerization rate decreased and the hydroxy terminated rate increased.展开更多
The microstructures of the hybrid core-shell latex synthesized by emulsion copolymerization of 3-trimethoxysilyl propyl methacrylate（MPS） and styrene were investigated.The polymers obtained under different operating...The microstructures of the hybrid core-shell latex synthesized by emulsion copolymerization of 3-trimethoxysilyl propyl methacrylate（MPS） and styrene were investigated.The polymers obtained under different operating conditions were characterized by（）29Si solid state NMR,FTIR,DSC and elemental analysis.It was found that under a neutral condition all of the MPS monomers were copolymerized into the polymer chain,small part of SiOR groups were hydrolyzed into SiOH groups and crosslinked by hydrogen bonds,the content of crosslinking is increased by MPS addition amount.Under basic condition,part of MPS were hydrolyzed and condensed into oligomers firstly,then these resultants were grafted into the polymer chain as pendent chain by both free radical polymerization and hydrolysis-condensation reaction.And under acidic condition,MPS in the system was easily hydrolyized and acted as crosslinker so that the emulsion became gels rapidly.展开更多
文摘The anionic polymerization of octamethylcyclotetrasiloxane （D4） catalyzed by tetramethyl ammonium hydroxide （TMAH） in the presence of water under the conditions of high temperature and oxygen-off was investigated. The conversion of polymerization and the molecular mass of the polymer were examined by Gel Permeation Chromatography （GPC）. Based on mechanism analysis,the calculation model of terminated hydroxy concentration （ c OH ） was obtained. And the result of the increase of c OH with conversion was observed by using the model. Then the influence of reaction conditions on the change of the value of c OH with conversion was investigated.The increase of the hydroxy terminated rate was greater than that of the polymerization rate with increasing temperature.The increase of the polymerization rate was greater than that of the hydroxy terminated rate with the concentration of catalyst increasing. With the concentration of water increasing,the polymerization rate decreased and the hydroxy terminated rate increased.
文摘The microstructures of the hybrid core-shell latex synthesized by emulsion copolymerization of 3-trimethoxysilyl propyl methacrylate（MPS） and styrene were investigated.The polymers obtained under different operating conditions were characterized by（）29Si solid state NMR,FTIR,DSC and elemental analysis.It was found that under a neutral condition all of the MPS monomers were copolymerized into the polymer chain,small part of SiOR groups were hydrolyzed into SiOH groups and crosslinked by hydrogen bonds,the content of crosslinking is increased by MPS addition amount.Under basic condition,part of MPS were hydrolyzed and condensed into oligomers firstly,then these resultants were grafted into the polymer chain as pendent chain by both free radical polymerization and hydrolysis-condensation reaction.And under acidic condition,MPS in the system was easily hydrolyized and acted as crosslinker so that the emulsion became gels rapidly.
