Surface-dependent effect of functional silica fillers on photocuring kinetics of hydrogel materials

Two types of silica: precipitated (P, prepared in non-polar media, a new type, submicrometer sized) and fumed (F, nanosized), both unmodified and surface modified are investigated as functional fillers for potential applications in nanocomposites with poly(2-hydroxyethyl methacrylate) matrix. Special attention is paid to the kinetics of composite formation in an in situ photopolymerization process. Silica-containing formulations polymerize faster; this effect is much stronger for silica P having much larger particle size than silica F. Surface treatment leads to further acceleration of the polymerization in case of silica P but to retardation in case of silica F; the effect of modification of the filler surface on properties of composites is different for each of the silicas. The obtained results are discussed in terms of effects of curvature of silica particles, surface properties, solvation cell, interphase region, viscosity changes, and morphology of the resulting composites.