The in situ generation of particles is an efficient way to prepare organic-inorganic hybrid materials. This approach has been widely used to enhance the dispersion within the matrix and therefore to improve the composites' properties. This method was used in the present paper to produce silicone composites. The crosslinking of the polymer matrix was achieved by hydrosilation reaction that is typically the addition of a Si-H bond across a double bond, in the presence of a platinum catalyst. The generation of silica particles was carried out prior the hydrosilation reaction. We previously demonstrated that this usually thermally activated reaction can also be induced under UV-light and that a front propagation allows the formation of thick unfilled samples. However, the presence of inorganic particles directly dispersed in the matrix lead to a reduction of thickness curability. That is the reason why the addition of particles by sol-gel process is studied in the present article. The lower dimension and better dispersion of the particles within the material promote the formation of thicker cured composites. The effect of the silica precursor's amount on the system's reactivity was evaluated and samples thick up to 2 cm were obtained with the most suitable conditions of reaction. POLYM. ENG. SCI., 56:3-8, 2016. (c) 2015 Society of Plastics Engineers