A series of copolymers, polydimethyldiphenylsiloxane-alpha,omega-diols, differing by compositions and molecular masses has been prepared by equilibrium anionic ring-opening copolymerization of octamethylcyclotetrasiloxane with octaphenylcyclotetrasiloxane in presence of tetramethylammonium hydroxide as a catalyst. These copolymers were used as matrix for the in situ developing silica networks. The crosslinking of the copolymers concomitantly occurs by reaction between the ending silanol groups and tetraethoxysilane, thus the polydiorganosiloxane network interconnects with the silica one. The resulted materials processed as films (thickness 0.25-1.50 mm) were investigated by various techniques in order to evaluate morphology, optical properties, and thermal behavior. The results were compared with those obtained by model samples based on polydimethylsiloxanes/silica.