Synthesis and Characterization of Silica Aerogel-Dispersed Random Poly(styrene-co-butyl acrylate) Nanocomposites by Atom Transfer Radical Copolymerization: A Reverse Approach

Abstract

Hexamethyldisilazane (HMDS) was employed to surface modification of hydrophilic silica aerogel nanoparticles. Then, the resultant HMDS-modified silica aerogel nanoparticles were used for in situ reverse atom transfer radical copolymerization. Fourier transform infrared spectroscopy, nitrogen adsorption/desorption isotherm, scanning and transmission electron microscopy were employed to evaluate unique characteristics of the HMDS-modified silica aerogel nanoparticles. According to the kinetics results, adding of HMDS-modified silica aerogel nanoparticles by 3 wt% results in a decrease of conversion from 97 to 74 % and molecular weight of copolymer chains from 11,770 to 8384 g mol−1; however, polydispersity index values increases from 1.32 to 1.74. Copolymers composition was evaluated using 1H NMR spectroscopy. TGA results indicate that by increasing HMDS-modified silica aerogel nanoparticles content, slight improvement in thermal stability of the nanocomposites were obtained. DSC results show a decrease in Tg from 39.96 to 30.61 °C by addition of 3 wt% HMDS-modified silica aerogel nanoparticles.