Rheology of Non-dilute Polystyrene/Cloisite/Toluene Solutions

We have previously described a simple model of spin casting for polymer/clay nanocomposite films in which the viscosity of the polymer solution at low solvent concentration is a critical parameter. We have therefore examined the shear dependent viscosity of polystyrene/Cloisite-6A/toluene solutions over a wide range of weight fractions, and for various molecular weights. The data is well described by the Carreau model $\eta -\eta _\infty =(\eta -\eta _0 )(1+\lambda ^2\dot {\gamma }^2)^{-N}$, where the parameters in the model show a clear dependence on the clay/PS ratio. We will discuss the trends observed in the viscosity data, and their impact on the uniformity of spin cast films.