Structural effects on the viscoelasticity of polydimethylsiloxane networks close to the sol-gel threshold

Polydimethylsiloxane (PDMS) networks were obtained by hydrosilation of a difunctional vinyl-terminated PDMS prepolymer with three crosslinkers of different functionality and molecular weight. These samples were studied using dynamic viscoelastic experiments as a function of time and frequency. Critical parameters were determined close to and ahove the sol-gel threshold. Rheological master curves could be built for the three PDMS networks above the gel point. The results obtained suggest that the critical exponents are not universal and depend on the chemical structure of the incipient networks.