A thermally stable and flexible composite has been synthesized by following a consecutive 'two-step', solvent free route. Silicone polymer containing internal hydrides was used as a polymer matrix and mesoporous silica functionalized with allytrimethoxysiloxane was used as a filler material. In the second step, the composite preparation was carried out using the hydrosilylation reaction mediated by 'Karastedt' platinum catalyst. The results of the studies suggest that the composites are thermally stable, hydrophobic and flexible and can be potentially used for encapsulating flexible electronic devices. © The Royal Society of Chemistry.