Apatite-forming ability and mechanical properties of PTMO-modified CaO-SiO₂ hybrids prepared by sol-gel processing: Effect of CaO and PTMO contents

Transparent monolithics of triethoxysilane end-capped poly(tetramethylene oxide) (Si-PTMO)-modified CaO-SiO₂ hybrids were successfully synthesized by hydrolysis and polycondensation of Si-PTMO, tetraethoxysilane (TEOS) and calcium nitrate. As for the samples with varying (Ca(NO₃)₂)/(TEOS) molar ratios under constant ratio of (Si-PTMO)/(TEOS) of 2/3 in weight, the apatite-forming ability in a simulated body fluid (SBF) which is indicative of bioactivity, remarkably increased with increasing CaO content, although the tensile strength and Young's modulus decreased. The hybrid with (Ca(NO₃)₂)/(TEOS)=0.15 in mol formed an apatite on its surface within only 1 day. For this series of samples, the strain at failure which is a measure of capability for deformation of material, was found to be about 30% and almost independent of CaO content. As for the samples with varying (Si-PTMO)/(TEOS) weight ratios under constant ratio of (Ca(NO₃)₂)/(TEOS) of 0.15 in mol, the strain at failure increased with increasing Si-PTMO content, but the apatite-forming ability, tensile strength and Young's modulus decreased. Thus, the synthesis of the hybrids exhibiting both high apatite-forming ability and high extensibility can be achieved by selecting suitable CaO and Si-PTMO contents. These new kind of hybrid materials may be useful as bioactive bone-repairing materials.