Adsorption and wetting on moveable walls

Polystyrene latex spheres, colloidally suspended at very low volume fraction in critical and nearcritical mixtures of 2,6-lutidine and water (LW), have been observed to segregate strongly into a complete wetting phase when the LW mixture is placed in its two-phase region near T_c. The wetting temperature, T_w, is observable as that at which colloidal particles abruptly begin to migrate to the meniscus. In the one-phase region near the coexistence temperature, the particles aggregate reversibly through a process which appears to be interpretable as a form of capillary condensation.