Preparation of silica-poly(2-hydroxyethyl methacrylate) hybrids modified with 3-methacryloxypropyltrimethoxysilane

Abstract

In this work we successfully prepared sol–gel derived organic–inorganic hybrids by the incorporation of poly(2-hydroxyethyl methacrylate) and 3-methacryloxypropyltrimethoxysilane into a silica matrix. The obtained samples were examined by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), differential scanning calorimetry (DSC), Nitrogen adsorption tests, and Vickers microhardness measurements. The incorporation of PHEMA and P(HEMA-co-MPS) into silica gave rise to samples with smaller specific surface areas and pore volumes when compared to pure silica. It was observed that materials prepared with polymer additions above 40wt% were virtually non-porous. These findings may be related to the blockage of silica pores by polymer chains in the hybrid materials. It seems that the initial addition of either PHEMA or P(HEMA-co-MPS) to silica caused a partial filling of its pore structure, leading to an increase of its microhardness. On the other hand, when these polymers are incorporated at concentrations above 20wt% it may occur a partial rupture of the silica framework, which decreases the microhardness of the processed materials. In addition, the increase of the polymer loading led to large polymer domains in the prepared samples. However, this behavior was less pronounced for hybrids modified with MPS.