Anomalous stress relaxation in random macromolecular networks

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Within the framework of a simple Rouse-type model we present exact analytical results for dynamical critical behaviour on the sol side of the gelation transition. The stress-relaxation function is shown to exhibit a stretched-exponential long-time decay. The divergence of the static shear viscosity is governed by the critical exponent k=ϕ-β, where ϕ is the (first) crossover exponent of random resistor networks, and β is the critical exponent for the gel fraction. We also derive new results on the behaviour of normal stress coefficients.