DSC study of polyhydroxyethylmethacrylate filled with modified silicas

Effects of the nature of functional groups (namely, hydroxyl, methyl, silicon hydride, amino, and vinyl) on the surface of pristine and modified silicas on polymerization of 2-hydroxyethylmethacrylate (HEMA) and on structural characteristics of the filled composites have been studied. DSC, FTIR spectroscopy and equilibrium water sorption (ESI) techniques were applied for the composites characterization. Results obtained testify that the chemical nature of the grafted groups has a strong influence on the monomer orientation in the surface layer of the filler. More uniform and cross-linked structures were detected in the composites with particularly methylated silica. Filler with chemically active silicon hydride groups promotes formation of ordered structure with rigid macromolecules. The presence of amino and vinyl groups on the silica surface results in formation of flexible polymer chains with a low cross-linking density or with a low polymerization degree, even at 2?wt% filling degree. Water uptake for composites with vinyl- and amine-containing silicas was low, indicating the close-packing of polymeric molecules in the filled polyHEMA.