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

By a combination of inorganic and organic species at a molecular level, a new series of biomaterials having optimal controllable properties can be fabricated. The goal of this work is to determine how the reactivity of the composites (inorganic–organic hybrids) can be controlled by altering the nanostructure 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 incorporating calcium and phosphate compounds. The properties of the hybrids were determined by swelling experiments, infrared spectroscopy, and scanning electron microscopy/microprobe analysis. Transparent PVA–silicate hybrid free-standing films, having a range of compositions within the system, were produced by allowing the rate of hydrolysis of the alkoxide to be compatible with the kinetics of the dissolution processes of both the polymer and calcium-phosphate compounds. Results obtained from swelling experiments and infrared spectroscopy showed that the crosslink density can be increased when hybrids are prepared with larger concentrations of the inorganic component. Moreover, hybrids prepared at temperatures as high as 60°C have, among other properties, greater crosslink densities and inorganic phases with larger amounts of S–O–Si bridging bonds. Swelling experiments also showed 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 hybrids such as the crosslink density, proportion of the phases and composition of the inorganic phase, among others.