next up previous
Next: Experimental Techniques Up: Interactions in Colloidal Suspensions: Previous: Interactions in Colloidal Suspensions:

Introduction

Charged colloidal particles suspended in water interact through hard core repulsions, van der Waals attractions, Coulomb interactions, and hydrodynamic coupling. The particles' influence on the surrounding medium modifies these interactions, for instance leading to screening of Coulomb interactions by atomic-scale simple ions. It also can give rise to entirely new effects such as entropically driven depletion interactions in heterogeneous suspensions. Bounding surfaces can modify all of these interactions, particularly if they carry their own charges. Competition and cooperation among these influences give rise to a bewildering variety of many-body phenomena including colloidal crystallization (of various kinds), gel formation (of various kinds), glass formation, and a host of collective responses to external forces and fields. Confidence in our ability to explain and control such cooperative behavior is undermined by the all-too-frequent discovery of new mysteries regarding colloidal interactions.

This contribution focuses on recent experimental investigations of interactions in dilute suspensions of monodisperse charge-stabilized spheres whose behavior should be governed principally by screened Coulomb and hydrodynamic interactions. Both classes of interactions have come under renewed scrutiny because of an accumulation of anomalous observations. For example, spheres carrying the same sign charge appear to attract each other under circumstances for which existing theories predict repulsion [1]. Such anomalies may highlight previously overlooked many-body contributions to colloidal dynamics.


next up previous
Next: Experimental Techniques Up: Interactions in Colloidal Suspensions: Previous: Interactions in Colloidal Suspensions:
David G. Grier 2001-01-16