Viscoelasticity of Near-Critical Gels

Viscoelastic measurements on gels near the gel point show power-law frequency and time dependences. Using a percolation model, we find that viscoelastic properties are described by the universal exponent Δ=dν(dν+k) where k is viscosity exponent, ν is the correlation-length exponent, and d is the dimension of space. This expression leads to a theory for the critical growth of the equilibrium shear modulus beyond the gel point, and the steady-state creep compliance beneath the gel point. Viscoelastic data are given for epoxy resins.