(142ce) Nonlinear Rheology of Colloid-Polymer Composites

Colloid-polymer composites have high potential application in improving mechanical properties of materials as an important class of complex fluid. Rules of controlling macroscopic flow properties of colloid-polymer composites are not well understood because of limited developed knowledge in the microscopic view of colloid interaction and polymer dynamics. Even less systematic study has been carried out to investigate the effect of particle size, interaction, concentration with varied polymer dynamics on nonlinear response of the composites under shear both theoretically and experimentally. Here we study the rheology of silica particles with varied size suspended in unentangled polymer melts by applying both continuous shear and dynamic shear. Before studying the dense suspension in which our particular interests are, low particle concentration condition is studied to understand the basic physics of particles interaction in dilute condition. When moving to high concentration system within the region of glass and weak gel formation where the difference is observed with polymer molecular weight tuned, significant difference is observed in the flow properties of the enhanced polymer melts. Specially, shear thickening behavior, nonlinear rheology and yielding behavior are searched to understand roles of particle concentration, size and polymer molecular weight in terms of confined particle and polymer dynamics.