Influence of Pendant Chains on Viscoelastic Properties of Model Networks

M.A. VILLAR

Gramado, Brasil

Simposio; XI International Macromolecular Colloquium y 6th Internacional Symposium on Natural Polymers and Composites; 2007

Model networks, with a well defined structure, were synthesized by reacting a commercial a,w-divinyl poly(dimethylsiloxane) (B2) with a trifunctional (A3) or tetrafunctional (A4) cross-linker bearing silane groups and known amounts of an anionic w-vinyl poly(dimethylsiloxane) (B1). The structure of the networks was predicted with a molecular model based on a mean field approach (recursive model) taking into account the initial concentration of the reactants. Rheological characterization was carried out in a rotational rheometer by dynamic and stress relaxation test. Viscoelastic properties of the networks depend on both concentration and molecular weight of pendant chains. Relaxation modulus was adjusted by the empirical Chasset-Thirion equation. It was found that it provides a very good fit to the behavior of networks prepared by end-linking. The fitting parameter m in the Chasset-Thirion equation shows a strong dependence with the molecular mass of pendant chains, but it is roughly independent of concentration