(252i) Phase Behavior and Percolation in Mixed Patchy Colloids

Ordered colloidal structures have a variety of applications, such as chemical catalysis, optical imaging, controlled drug delivery, and emulsion stabilization. Mixed patchy colloids offer the opportunity to self-assemble these and other structures from solution. Due to short range and directional interactions, patchy colloids can associate with each other to form colloidal clusters of various sizes and configurations. Further aggregation will lead to the formation of infinite clusters or gels. Gelation, as a phenomenon, has opened new avenues for synthesis of materials with valued properties. The primary model of the aggregation and phase behavior of patchy colloids is our SAFT (statistical associating fluid theory) model, an extension of simplification of Wertheim’s first order thermodynamic perturbation theory (TPT1). As predicted by SAFT, patchy colloids show a variety of novel physical phenomena such as re-entrant phase behavior, gelation, empty liquid regime and network formation. In recent work, Zhu, et al have developed a SAFT based model to predict the solid, liquid, gas phase diagram for patchy colloids. However, due to assumptions in TPT1 that association sites are independent and that every site can only bond once, TPT1 loses accuracy when there are correlations between association sites on the same molecule and when sites are large enough to form multiple bonds. This is due to lack of multibody correlations (i.e., beyond pair correlations) in TPT1. Bansal et al have developed a cluster distribution theory (BAMC) that includes multiply body correlations to study binary patchy colloids in which one of the components can have association patches of any size and of any geometry. In this work, we extend this multibody theory with the Flory-Stockmayer theory to study the gelation of binary patchy colloids system. Percolation threshold and novel phase behavior has been further investigated in this work.