Stress relaxation of polymer networks containing low concentrations of dangling chains and star shaped polymers

D.A. VEGA; L.R. GÓMEZ; M.A. VILLAR; E.M. VALLÉS

Los Angeles, USA

Congreso; 2005 March Meeting of the American Physical Society; 2005

American Physical Society

We analyze the influence of low concentrations of star and dangling polymers on the stress relaxation process of model polymer networks. Model PDMS networks with well defined structure were obtained by the hydrosylilation reaction, based on the addition of hydrogen silanes from the cross-linker molecules to end vinyl groups present in the prepolymer molecules. Rheological characterization was carried out in a rotational rheometer by dynamic and stress relaxation test. Viscoelastic properties of the networks depend strongly on the molecular weight of the stars or pendant chains. It was found that a modified Pearson-Helfand model provides a very good fit to the behavior of these networks.  This model incorporates the effect of higher Rouse modes on the arm retraction [Milner and McLeish, Macromolecules, 1997] and the potential for arm retraction originally proposed by Doi and Kuzzu.