Apatite-forming ability and mechanical behavior of PTMO-modified CaO-TiO₂ hybrids prepared by sol-gel processing

Triethoxysilane end-capped poly (tetramethylene oxide) (Si-PTMO)-modified CaO-TiO₂ hybrids were prepared by hydrolysis and polycondensation of Si-PTMO, tetraisopropyltitanate (TiPT) and calcium nitrate. Under constant ratio of(Si-PTMO) / (TiPT) = 2/3 in weight, the molar ratio of(Ca(NO₃)₂)/(TiPT) was varied from 0 to 0.15. The apatite-forming ability was evaluated in a simulated body fluid (SBF) and the mechanical properties including Young's modulus, strength and strain at failure were measured in air by three-point bending test. The apatite-forming ability in SBF remarkably increased with increasing CaO content, although the bending strength and Young's modulus decreased. The hybrid samples with (Ca(NO₃)₂)/(TiPT) = 0.10 and 0.15 in mol, respectively, formed the apatite on their surface within only one day. The failure strains were found to be in the range of about 13 to 25%. Thus, the hybrids exhibiting both high apatite-forming ability and high capability for deformation were successfully synthesized. These hybrids may be useful as new kind of bioactive bone-repairing materials.