Static and dynamic properties of cross-linked poly(dimethylsiloxane) pregel clusters

Experimental results concerning end-linked poly(dimethylsiloxane) pregel clusters quenched at different distances from the gelation threshold are reported. Static and quasielastic light scattering experiments and intrinsic viscosity measurements allow us to verify that static properties of this chemical system are properly described by the percolation model. The critical behavior of the rheological properties is investigated with particular attention to the temperature and concentration dependence of the exponent values. It is shown that in this chemical system, local dynamic properties are independent of the distance to the threshold, allowing "real" exponents to be evaluated. One finds that the exponents governing the divergence of the viscosity, s, the emergence of the elastic modulus, t, and the frequency dependence of the elastic modulus, u, are equal to s = 1.1 ± 0.06, t = 1.9 ± 0.15, and u = 0.69 ± 0.005.