镍体系(NiCl_2/PPh_3)催化的表面引发反向原子转移自由基聚合制备有机/无机杂化材料

Surface Initiated Reverse ATRP to Prepare Organic/Inorganic Hybrid Composite Catalyzed by NiCl_2/PPh_3 System

考察了以过氧基团改性的纳米SiO2为引发剂,NiCl2/PPh3为催化体系的甲基丙烯酸甲酯(MMA)的反向原子转移自由基聚合(ATRP).通过纳米SiO2与氯化亚砜反应,得到了表面由氯-硅基团改性的纳米SiO2,然后再将其与叔丁基过氧化氢(TBHP)反应,在纳米二氧化硅表面成功引入过氧基团,得到了过氧基团改性的纳米SiO2粒子.结果表明,通过调控Ni2+和Ni+之间的变价关系,使得整个聚合反应具有活性自由基聚合的特征.通过酯交换反应,即将聚甲基丙烯酸甲酯接枝的纳米SiO2杂化粒子与氢氟酸反应,可将聚合物层从二氧化硅粒子表面成功解离.GPC结果表明,该纳米材料聚合物接枝层的分子量基本可控,分子量与单体转化率呈线性关系,ln([M0]/[M])与反应时间成正比,两者成线性关系.AFM分析表明,聚合后聚合物链均匀接枝到纳米SiO2表面,得到了分散稳定的以二氧化硅粒子为核,聚甲基丙烯酸甲酯为壳的核壳杂化粒子.

In this work, reverse atom transfer radical polymerization of methyl methacrylate was investigated by using the peroxide groups treated nano-silica as the initiator and NiCl2/PPh3 as the nickel based catalyst. The introduction of peroxide groups onto the silica surface was achieved by the reaction of hydrogen peroxide with chlorosilyl groups, which were introduced by the treatment of silica with thionyl chloride. The results indicate that through control the relationship of Ni^2＋ and Ni ^＋ , the polymerization was closely controlled and partly has the characteristic of ＂living＂/ controlled radical polymerization. Hydrolysis of silica cores by hydrofluoric acid treatment enabled characterization of cleaved polymer using GPC. The GPC analysis indicated that the MnGPC of PMMA （grafted） increases linearly with the increase of conversion and the molecular weight distributions are relatively narrow. The kinetics of the polymerization showed one order, suggesting that the active species kept constant during the polymerization. AFM results indicate that well-defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined outer polymer layer.