Microstructure and macroscopic properties of bioactive CaO-SiO2-PDMS hybrids

CaO-SiO2-PDMS (polydimethylsiloxane) hybrid materials were synthesized as crack-free monoliths presenting in vitro bioactivity, i.e. able to be coated with a calcium phosphate-rich layer after having been soaked in simulated body fluid (SBF). A wide physical-chemical characterization of these materials was carried out to relate their microscopic structure and macroscopic properties. The effect of PDMS and the amounts of water used for the tetraethoxysilane (TEOS) hydrolysis on the mechanical properties of hybrid materials was investigated by three-point bending tests. For a given amount of water, as PDMS content in hybrids increased, the elastic modulus decreased. Furthermore, keeping the PDMS content constant, when the amount of H2O decreased, the elastic modulus increased. Regarding in vitro bioactivity and mechanical properties, the hybrid material obtained with molar ratios H2O/TEOS = 2 and TEOS/PDMS = 3.5 proved to be the best candidate for either soft tissue substitution or metallic implant coating since the hybrid material would promote bond to bone formation, simultaneously dampening the mechanical charges.