Dynamical critical behavior during chemical gelation and vulcanization

Critical behavior in gelation and vulcanization of polymers is discussed in the context of polymeric fractals. Dynamic mechanical measurements show that in the critical region a power law in the complex viscosity and in the modulus appears. Viscosity and modulus are calculated around the critical point and as functions of the extent of reaction. The power law is interpreted in terms of the fractal dimension of the cluster, and it is shown that this agrees with experiment if one takes swelling phenomena into account.