Synthesis of Hybrid Organic−Inorganic Materials from Interpenetrating Polymer Network Chemistry

Organic−inorganic interpenetrating polymer networks were synthesized with an SiO 2 phase made by sol−gel chemistry and the organic phase made from poly(2-hydroxyethyl acrylate). The resultant morphologies were characterized by small-angle scattering and electron microscopy. When the vinyl polymerization is more rapid than the sol−gel reaction, gross phase separation occurs giving a heterogeneous structure. For comparable rates of the two polymerizations, the specimens have a dendritic morphology on the scale of 0.5 μm. The more rapid formation of the silica phase relative to the organic network produces rigid and optically transparent materials, with a finely divided structure as seen by transmission electron microscopy. The glass content of these materials is about 0.15 g/g and the sizes of the SiO 2 -rich domains are 100 Å or less. Addition of tetrakis(2-(acryloxy)ethoxy)silane was also studied and found to promote phase mixing between the organic and inorganic phases.