Polystyrene--Polydimethylsiloxane as a Potential Silica Substitute for Polysiloxane Reinforcement.

Here we report microphase-separated poly(styrene--dimethylsiloxane) (PS--PDMS) as a reinforcing filler in PDMS thermosets that overcomes the long-standing problem of aging in the processing of silica-reinforced silicone. Surprisingly, PS--PDMS reinforced composites display comparable mechanical performance to silica-modified analogs, even though the modulus of PS is much smaller than that of silica and there is no evidence of percolation with respect to the rigid PS domains. We have found that a few unique characteristics contribute to the reinforcing performance of PS--PDMS.