Glass transition and hydration properties of polyhydroxyethylmethacrylate filled with modified silica nanoparticles

Abstract

Effects of the filling degree of nanodispersed silica functionalized with amino or vinylsilyl groups on polymerization of 2-hydroxyethylmethacrylate (HEMA) and on structural characteristics of the filled composites have been studied using DSC, FTIR spectroscopy and equilibrium water sorption techniques. The results obtained testify that the kinetics of surface reaction as well as the structure of the boundary layer has more significant effect on composite structure than mechanical strengthening realized by the increase in filling degree. Merging the results of thermal analysis with data on the sorption capacity suggests the formation in filled polymer of pseudo-crystalline structures in condition of cohesion energy reduced, and this process does not depend strongly on filling degree. In the case of vinyl-silica, chemical bonding of monomer HEMA to surface that isolated nanoparticles can be niggled structuring effect of filler as reinforcing material. With increasing the filling degree of polymer with silica-amino, the nature of the polymer–silica interaction changes, with highest cohesive energy for the composite with filler content around 3 mass%. It was found that samples characterized by lowest cohesive energy have lowest moisture loss during desorption.