甲基丙烯酸甲酯/苯乙烯在硅片表面的RAFT接枝聚合

将3-(2-二硫代苯甲酸基丙酰氧基)丙基二甲基甲氧基硅烷化学键合于硅片表面.以甲基丙烯酸甲酯和苯乙烯为单体,在硅片表面进行可逆加成-断裂链转移(RAFT)接枝聚合.X-射线光电子能谱仪证实聚甲基丙烯酸甲酯(PMMA)、聚苯乙烯(PS)、苯乙烯/甲基丙烯酸甲酯的共聚物(poly(MMA-co-St))都接枝到硅片表面.但3个体系表现出不同的性质,甲基丙烯酸甲酯的RAFT聚合可控性差,分子量比设计分子量大得多,分子量分布指数宽,接枝密度仅为0·03chains/nm2;苯乙烯均聚合的活性/可控性好、分子量分布窄,接枝密度提高到0·21chains/nm2;共聚合体系综合了两个均聚体系的优点,分子量分布较窄,接枝密度最高为0·31chains/nm2,聚合物膜厚随转化率、数均分子量基本呈线性增长.

RAFT GRAFTING POLYMERIZATION OF MMA/St FROM SURFACE OF SILICON WAFER

Polystyrene(PSt),polymethylmethacrylate(PMMA) and copolymers(poly(MMA-co-St)) were grafted from silicon wafer via RAFT agent that was anchored to the surface.X-ray photoelectron spectroscopy showed that while the polymers were successfully grafted,the control of polymer molecular weight(MW) behaved very differently.The Si-PMMA system yielded MW much higher than the theoretically targeted,broad molecular weight distribution and low grafting density(ca.0.03 chains/nm2).In contrast,the Si-PSt system gave MW close to the theoretical value with polydispersities around 1.3.The grafting density increased to 0.21 chains/nm2.In Si-poly(MMA-co-St) system,the polymer layer thickness increased linearly with monomer conversion and molecular weight of free polymer in solution,suggesting that the RAFT copolymerization grafting of MMA and St from silicon wafer was well controlled.The MW was close to the theoretical value.The grafting density reached 0.31 chains/nm2,which was higher than those obtained in their homo-polymerizations.