Anomalously Large Equilibrium Clusters of Colloids

We propose a mechanism for mesophase separation in a system of aggregating colloids. Conditions are outlined under which colloids can form equilibrium clusters with very large sizes, i.e., aggregation numbers of a thousand or more. The driving force for clustering is a short range attractive interaction which will be treated within a capillarity approximation. The stabilizing mechanism is a small amount of charge per particle. Under the appropriate conditions these charges will interact with unscreened Coulomb potentials and, consequently, prevent large-scale phase separation.