高分散性SiO_2/PMMA复合材料的制备与表征——接枝与交联

PREPARATION AND CHARACTERIZATION OF SILICA/PMMA COMPOSITES WITH HIGHLY DISPERSED SILICA——GRAFTING AND CROSSLINKING

以硅烷偶联剂3-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPS)改性SiO2/甲基丙烯酸甲酯(MMA)分散液为原料,通过原位本体聚合制得一系列具有不同SiO2含量和PMMA接枝率的高分散性SiO2/PMMA复合材料,索氏抽提分析复合材料的接枝和交联情况.发现抽提后体系中主要存在3部分物质:抽提液中含游离SiO2的PMMA溶液,附于滤纸袋内表面上含接枝SiO2的PMMA薄膜,溶胀于滤纸袋内含交联SiO2的PMMA凝胶,且PMMA和SiO2在上述3部分中的分配百分率明显受SiO2含量和其表面MPS偶联率的影响.再计算凝胶和薄膜中SiO2的接枝率,氢氟酸刻蚀SiO2后凝胶渗透色谱(GPC)测量相应接枝链的分子量,进而评估不同部分中SiO2颗粒表面接枝链的接枝密度.发现相对于薄膜中的SiO2,凝胶中SiO2表面PMMA接枝率较高、分子量较大、接枝密度稍大.认为上述现象与SiO2颗粒表面由偶联MPS引入的PMMA接枝,以及这些接枝链间的化学键合密切相关.特别是当SiO2含量和MPS偶联率较高时,复合材料的局部乃至整体可形成以SiO2颗粒为交联点的立体交联结构.

A series of 3-（trimethoxysilyl）propyl methacrylate（MPS） modified silica/poly（methyl methacrylate） composites（SiO2/PMMA） with different silica content and PMMA grafting percentage were prepared via in situ bulk polymerization.The grafting and crosslinking status of the composites were analyzed by Soxhlet extraction,and three parts were found：PMMA solution with free silica in extract solvent,PMMA film with connected silica on the inner wall of filter bag,PMMA gel with crosslinked silica in the inner of filter bag.The distribution of PMMA and silica in the above three parts were obviously affected by the silica content and PMMA grafting percentage.Based on the etching of silica by HF,the PMMA grafting percentage,the molecular weight of grafted PMMA and the grafting density of PMMA chain on different silica particles were measured by gravimetric method and gel permeation chromatography（GPC）.The grafting percentage,molecular weight and grafting density of PMMA in gel were more than those in film,and the grafting density of PMMA chain both in gel and in film were close with the one of MPS in silica/MMA dispersion.The above phenomena can be attributed to the grafting of PMMA from the anchored MPS on silica surface and the chemical bonding between the PMMA chains grafted on different silica.Especially,in the case of higher silica content and higher MPS coupling amount,a three-dimensional crosslinked structure with silica as crosslinking point can be easily formed in the part and even in the whole of the SiO2/PMMA composite.The regulation to the grafting and crosslinking structure was of benefit to improving the composites properties,especially to the dispersibility of the accumulated silica on the melting shear field.