微滴乳液聚合制备纳米SiO2/聚丙烯酸酯复合材料

在硅溶胶中加入八甲基环四硅氧烷(D4)和偶联剂γ-(2,3-环氧丙氧) 丙基三甲氧基硅烷(KH560),以十二烷基苯磺酸(DBSA)催化D4的开环聚合,借助超声强化聚二甲基硅氧烷(PDMS)和偶联剂对硅溶胶的表面改性。将改性硅溶胶及其混合物分散在甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)的混合单体中,实施微滴乳液聚合,制备SiO₂/聚丙烯酸酯纳米复合材料。硅溶胶改性阶段的催化剂中和后成为后续微滴乳液聚合的乳化剂,而伴生的PDMS成为有效抑制单体珠滴Ostwald 熟化的超疏水剂。采用FTIR、TGA、TEM、马尔文纳米粒度仪、水接触角等测试方法对改性纳米粒、复合胶乳和胶乳薄膜进行表征。结果表明,PDMS和偶联剂在SiO₂表面形成了共价键合和包覆,且伴生的PDMS改善了复合胶乳薄膜的表面疏水性,复合粒子是聚合物基体为壳、SiO₂纳米颗粒呈海岛分散的 (多)核-壳结构形态,SiO₂占单体质量分数为3%时,平均粒径约98 nm。

Preparation of nano-SiO2/polyacrylates composites via miniemulsion polymerization

With the ultrasonic assistance, octamethylcyclotetrasiloxane(D4)and a little of silane coupling agent γ-(2, 3-epoxypropoxy) propyltrimethoxysilane (KH560) were sufficiently mixed with silica sol and the in-situ ring-opening polymerization of D4 and co-condensation with KH560 on the surface of silica nanoparticles, catalyzed by dodecylbenzene sulfonic acid (DBSA), were enhanced as well. The polydimethylsiloxane (PDMS) modified silica was obtained. The PDMS-modified silica sol was dispersed in the mixed monomers of methylmethacrylate (MMA) and butylmethacrylate (BA). Then miniemulsion polymerizations of the acrylate monomers containing PDMS-modified silica sol were carried out, with PDMS as hydrophobe to inhibit the Ostwald ripening of the monomer droplets and neutralized DBSA as emulsifier, both preexisted in the PDMS-modified silica sol. The SiO₂/polyacrylates composite latex was obtained via miniemulsion polymerization. FTIR, TGA, TEM, Malvern Nanosizer and water contact angle tests were utilized to characterize the modified silica and the composite latex. The results show that silica is grafted and encapsulated by PDMS and KH560 with chemical bonds and is well dispersed in monomers, and the generated PDMS improves the hydrophobicity of the film of nanocomposite latex. The average size of nanocomposite particles with a (multi)core-shell structures is 98 nm when the silica mass fraction is 3% of the monomers.