(525b) Entropy Compartmentalization of Open Host-Guest Colloidal Clathrates with Rotating Guest Particles

Clathrates are open crystals in which atoms and molecules are arranged in a hierarchy of polyhedral cages. In this study, we report the entropy-driven self-assembly of new open-caged host-guest colloidal clathrate crystals. In Monte Carlo simulation, hard truncated triangular bipyramids (TBPs) self-assemble into five clathrates where guests and hosts are the same species. Crystallization occurs via entropy compartmentalization, where the entropy of the system partitions into a low entropy (host particle) subsystem and a high entropy (guest particle) subsystem with rotating guests. The type of clathrate depends on the amount of truncation, which determines the guest/cavity size ratio, while the dynamical behavior of the guests depends on the shape and symmetry of the guest and cavity. When TBPs are mixed with another particle shape, the traditional host-guest structure self-assembles, again driven by entropy maximization via subsystem compartmentalization.