Novel multicomponent silicate-poly(vinyl alcohol) hybrids with controlled reactivity

By a combination of inorganic and organic species at a molecular level, a n ew series of biomaterials having optimal controllable properties can be fab ricated. The goal of this work is to determine how the reactivity of the co mposites (inorganic-organic hybrids) can be controlled by altering the nano structure of the materials. Hybrids were synthesized by reacting poly(vinyl alcohol) (PVA) in acidic solution with either tetraethoxy silane (TEOS) or tetramethoxy silane (TMOS). The inorganic phase was also modified by incor porating calcium and phosphate compounds. The properties of the hybrids wer e determined by swelling experiments, infrared spectroscopy, and scanning e lectron microscopy/ microprobe: analysis. Transparent PVA-silicate hybrid f ree-standing films, having a range of compositions within the system. were produced by allowing the rate of hydrolysis of the alkoxide to be compatibl e with the kinetics of the dissolution processes of both the polymer and ca lcium-phosphate compounds. Results obtained from swelling experiments and i nfrared spectroscopy showed that the crosslink density can be increased whe n hybrids are prepared with larger concentrations of the inorganic componen t. Moreover, hybrids prepared at temperatures as high as 60 degrees C have, among other properties, greater crosslink densities and inorganic phases w ith larger amounts of S-O-Si bridging bonds. Swelling experiments also show ed that the obtained hybrids varied in their reactivities ranging from fast dissolution to hydrogel properties. We also demonstrate that the degree of reactivity can be controlled by manipulating structural factors of the hyb rids web as the crosslink density, proportion of the phases and composition of the inorganic phase, among others. (C) 2000 Elsevier Science B.V. All r ights reserved.