(105g) A Design Strategy for Open Colloidal Structures

Entropically driven self-assembly of hard anisotropic particles, where particle shape gives rise to emergent valencies, provides a new degree of freedom for the design of nanoparticle and colloidal systems. To date, hard particles have been observed to self-assemble into a rich variety of crystal structures, ranging in complexity from simple close-packed structures to structures with 432 particles in the unit cell. Entropic crystallization of open structures, however, is missing from this landscape. Here, we report on the self-assembly of a 2D, binary mixture of hard particles into an host–guest structure, where concave “host” particles form a honeycomb lattice that encapsulates smaller “guest” particles. Notably, this open structure forms in the absence of enthalpic interactions, providing one of the first examples of the self-assembly of such a structure in an athermal system. We discuss the various entropic stabilization effects present in this system, and show that both the concavity of the host particle and the presence of the guest particle are required for self-assembly. Our findings provide a strategy for designing binary colloidal systems of anisotropic particles that exhibit co-crystallization, and can be used as a template for selective dissolution into porous, ordered colloidal networks.