Rheology and dynamics of particles in viscoelastic media

Recent developments in the fundamental understanding of the rheology and dynamics of particles in viscoelastic media are reviewed. Suspensions of particles dispersed in a complex fluid matrix are central to applications in the area of coatings, pharmaceuticals, filled polymer melts, nanocomposites and biomaterials. Recent studies have established the range of validity of the generalized Stokes-Einstein equation to describe the relationship between the linear rheological behavior of the viscoelastic medium and the displacement of dispersed particles due to applied oscillatory or fluctuating forces. The extension of such microrheological methods to account for interactions between particle pairs is discussed. The scope for practical implementation of microrheology to characterize viscoelasticity in particle/complex fluid mixtures used in the aforementioned applications is assessed. (C) 2001 Elsevier Science Ltd. All rights reserved.