Structural characterization of PDMS–TEOS–CaO–TiO2 hybrid materials obtained by sol–gel

Abstract Hybrid materials of the polydimethylsiloxane (PDMS)–Tetraethyl orthosilicate (TEOS) system have already been widely described by several authors, being their potential for biological applications largely studied. For some bone related applications, the addition of Ca to these systems is commonly accepted as necessary for the enhancement of bioactivity. However Ca is commonly introduced in the form of calcium nitrate, which requires a heat treatment step in order to eliminate the nitrate residues. The aim of the present work is to produce a PDMS–SiO 2 –CaO–TiO 2 hybrid material through a sol–gel process, for potential biomedical applications. Calcium nitrate was used as the calcium source and to avoid the presence of nitrate residues in the final product, a heat-treating step at 400 °C was performed. Titanium was added to the hybrid system in order to enhance the thermal stability of the materials subjected to this temperature. TGA, FT-IR and 29 Si NMR techniques were used to understand the role of the calcium and titanium in the structure formation, and the way they influence the thermal stability of the PDMS–SiO 2 system. A final material containing calcium, with no traces of nitrate and the maintenance of a significant amount of methyl groups was successfully obtained.