AbstractIf the tetraethylorthosilicate (TEOS) used to end link hydroxyl‐terminated poly(dimethylsiloxane) chains is present in excess, there are two effects on the resulting network structure. First, some of the excess TEOS hydrolyzes to givein situprecipitation of reinforcing silica particles. In addition, some can cause extension of the polymer chains, particularly of the shorter chains in the case of a bimodal network. In the present investigation, the ultimate strength and toughness of such bimodal networks was found to go through a maximum with increase in the amount of excess TEOS used in the curingfilling procedur