Competing interactions in colloidal suspensions

Abstract

The purpose of colloid science is to understand the underlying mechanisms involved in the formation of ordered arrangements of particles, and to observe the self-assembly process in systems of components larger than molecules. A major focus of colloid science has been on understanding the forces between colloidal particles suspended in a fluid. For a long time, the main obstacle to verifying theories of colloidal forces has been the lack of experimental methods capable of directly measuring the forces between colloidal particles separated by a gap of few nanometers. Recently, advances have been made with new imaging techniques revealing some of the secrets of the spontaneous formation of pattern in homogeneous fluids. During the same time, models of interactions have been developed and tested on macroscopic observations of suspensions after changing their composition. It is clear that a general theory for the forces may not be suitable for all systems, as their characteristics are highly dependent on chemistry and the microscopic environment. In colloidal suspensions, it is now well established that an attractive interaction at distances slightly larger than the particle size is dominated by a repulsive contribution at larger distances. The competition between attraction and repulsion forces is responsible for the appearance of stable clusters of generic aggregation numbers. This paper is intended to provide (i) evidence of the confidence of potential models with competing attractive and repulsive interactions and (ii) appropriate tools for finding intriguing phenomena in the generation of nanostructures.

Keywords

• colloidal suspensions
• microemulsions
• diblock copolymers
• density fluctuations
• static structures