Influence of Pendant Chains on Mechanical Properties of Model Poly(dimethylsiloxane) Networks. 2. Viscoelastic Properties

Abstract

Viscoelastic properties of model poly(dimethylsiloxane) networks with pendant chains composed of linear molecules of known and uniform molecular weights are studied. It was found that the loss modulus (G‘‘) of these networks depends on the concentration and the molecular weight of the dangling chains. The dependency of the relaxation times of pendant chains on their molecular weights, proposed by de Gennes, was verified using the values of G‘‘ measured experimentally. Elastic properties of these networks decrease due to the presence of the pendant chains. This results in a reduction in the amount of elastically active chains. Low-frequency elastic moduli of the networks are coincident with equilibrium values predicted by the theory of rubber elasticity, provided that the contribution of trapped entanglements is taken into account. Values of elastic moduli obtained from swelling experiments also show excellent agreement with theoretical values.