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Two PDMS-SiO2-TiO2-Cao porous hybrid materials were prepared using the same base composition, precursors, and solvents, but following two different sol-gel procedures, based on the authors' previous works where for the first time, in this hybrid system, calcium acetate was used as calcium source. The two different procedures resulted in monolithic materials with different structures, microstructures, and surface wettability. Even though both are highly hydrophobic (contact angles of 127.2 degrees and 150.6 degrees), and present different filling regimes due to different surface topographies, they have demonstrated to be-cytocompatible when tested with human osteoblastic cells, against the accepted idea that high-hydrophobic surfaces are not suitable to cell adhesion and proliferation. At the nanoscale, the existence of hydrophilic silica domains containing calcium, where water molecules are physisorbed, is assumed to support this capability, as discussed. (C) 2016 Elsevier B.V. All rights reserved.

The last two decades have seen a remarkable growth in the design of new hybrid materials applied to different areas, from photonics to biomaterials, together with new coating materials with self-cleaning features. Among the various systems studied, the PDMS-SiO2 system remains as a good basis for further developments by adding other compounds such as transition metals. In this work, a detailed study of the influence of titanium or zirconium in the chemical structure and final microstructure of such hybrids was made. It was concluded that, due to the lower reactivity of the titanium alkoxide during the sol-gel preparation process, titanium is preferably located on the surface of secondary particles of silica, unlike the zirconium, which being more reactive, positions on the surface of the primary particles. This difference leads to xerogels with dissimilar characteristics and morphologies. (C) 2015 Elsevier Ltd. All rights reserved.

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-SiO2-CaO-TiO2 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 degrees 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 Si-29 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 -SiO2 system. A final material containing calcium, with no traces of nitrate and the maintenance of a significant amount of methyl groups was successfully obtained. (C) 2013 Elsevier B.V. All rights reserved.

International audience; Several conditions for the sol-gel polymerisation of hybrid silica-zirconia and silica-titania have been studied using specially tailored electrochemical probes. One of the probes has been designed to bind to the silica backbone, while the other has been designed to bind to the transition metal species. The results show that the silicon and the transition metal species play a quite different role in the polymerization course, and especially large differences between the zirconium and the titanium behaviour have been observed. It is shown unambiguously that while the zirconia species bind irreversibly to the silica gel, the titania, ones remain very mobile whatever the advancement of the reaction and probably act only as catalysts for the siloxane polycondensation.