Polyacrylate/SiO₂ nanocomposites prepared by combining non-aqueous sol–gel process and miniemulsion polymerization

Abstract

In this paper, Polyacrylate/SiO₂ nanocomposites were successfully prepared by combining non-aqueous sol–gel process of traethylorthosilicate (TEOS) and miniemulsion polymerization of acrylates. Firstly, the kinetics of non-aqueous sol–gel process of TEOS with formic acid (FA) as the catalyst was studied, which indicated that it was beneficial to obtain spherical silica sol particles when the molar ratio of FA to TEOS was above 6. According to the kinetics, the silica sol was prepared and in situ modified by 3-methacryloxypropyltrimethoxysilane (MPTMS), then in the presence of modified silica sol, the miniemulsion polymerization of acrylate was conducted and finally Polyacrylate/SiO₂ nanocomposite emulsion was obtained. The kinetics of the polymerization was discussed by measuring the conversion rate of monomers. The diameters and morphologies of the composite latex particles were analyzed by Nano particle analyzer and Transmission electron microscopy (TEM). Mechanical properties and glass transition temperatures (Tg) of the composite films were characterized by tensile test and differential scanning calorimetry (DSC). The results showed that the kinetics of the polymerization was similar as normal miniemulsion polymerization, however the introduction of silica sol reduced the homogeneity and the stability of the monomer droplets, the diameter and size distribution of the composite latex particles increased with the increasing content of silica. The morphologies of the composite latex particles were core-shell structures with silica particles encapsulated by polyacrylate. The introduction of nano-silica improved the mechanical properties and T_g of the composite films.