Shear-flow-induced microstructural distortion near the critical point

Shear-flow-induced microstructural distortion of suspensions close to the critical point is described in detail on the basis of the Smoluchowski equation, where hydrodynamic interaction is neglected. The solution of the Smoluchowski equation exhibits scaling behaviour, predicting that the combined shear rate and correlation length dependence is characterized by a single dimensionless number (with the shear rate and ξ the correlation length of the unsheared suspension). From the scaling relations for deformation of the structure factor, a scaling form for the turbidity is derived. Experiments concerning these phenomena are presented, some of which are prelimanary. Two types of systems are used, both of which exhibit a gas-liquid critical point: stearyl silica in benzene and stearyl silica in cyclohexane with polydimethylsiloxane. Although there is an overall agreement with the theory, there remains a discrepancy in some of the quantitative comparisons, probably due to the neglect of hydrodynamic interaction and the approximate nature of the closure relation that is used for the three-particle correlation function