Viscoelastic properties of silica-grafted poly(styrene–acrylonitrile) nanocomposites



The melt state viscoelastic properties of styrene–acrylonitrile random copolymers grafted to silica nanoparticles and prepared by in situ atom transfer radical polymerization are examined. Linear dynamic oscillatory viscoelastic measurements indicate that nanocomposites with silica contents as low as 1.2 vol % exhibit solid-like response. Steady shear results in considerable alteration to the mesoscale structure and results in the failure of the Cox-Merz rule. Flow reversal studies confirm the elastic nature of the mesoscale structure and demonstrate that the relaxation of the flow altered structure is slow, non-Brownian, and possibly cooperative. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2014–2023, 2006