Structure and aggregation of colloids immersed in critical solvents

摘要

We consider an ensemble of spherical colloidal particles immersed in anear-critical solvent such as a binary liquid mixture close to its criticaldemixing point. The emerging long-ranged fluctuations of the correspondingorder parameter of the solvent drive the divergence of the correlation length.Spatial confinements of these critical fluctuations by colloidal soluteparticles, acting as cavities in the fluctuating medium, restrict and modifythe fluctuation spectrum in a way which depends on their relativeconfiguration. This results in effective, so-called critical Casimir forces(CCFs) acting on the confining surfaces. Using the available knowledge aboutCCFs we study the structure and stability of such colloidal suspensions byemploying an approach in terms of effective, one-component colloidal systems.Applying the approximation of pairwise additive CCFs we calculate the radialdistribution function of the colloids, which is experimentally accessible. Weanalyze colloidal aggregation due to CCFs and thus allude to previousexperimental studies which are still under debate