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 $\Delta =\frac{d\nu }{(d\nu +k)}$ where $k$ is viscosity exponent, $\nu$ 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.