Engineering Entropy and Order in Colloidal Suspensions via Molecular Simulation
Fernando Escobedo (Cornell University)
Complex Fluids: Suspensions, Emulsions, and Gels
Wed 10:45 - 12:15
Barus-Holley 160
By elucidating structure-property relationships of colloidal materials, molecular simulations can assist the engineering of materials of desirable or “super” properties; e.g., those that originate in the creation of special types of structural order or the control of phase transitions. While molecular engineering often focuses on tuning chemical interactions, the engineering of entropic interactions is often equally crucial but less appreciated. In this presentation I will focus on mesophases formed by hard colloids (mesophases are materials whose structural order lies in between that of solids and liquids). Colloidal particles can form ordered solid and liquid phases that possess unique optical, rheological, and mechanical properties, making them attractive components in the preparation of novel composite, photonic, plasmonic, and photovoltaic materials. I will describe our recent efforts on the use of molecular simulations to map out the phase behavior and associated transition kinetics of suspensions of particles with polyhedral shapes. Our results provide both a basis to existing experimental observations and predictions of novel phases yet to be seen in the lab. In particular, we predict the formation of various novel entropy-driven self-assembling liquid- and plastic-crystalline phases which are resilient to particle size polydispersity. We also demonstrate that the “entropic bonds” associated with the tendency of flat facets to “parallel park” can be harnessed to realize a chemistry of colloidal self-assembly; e.g., to create “compound” phases by blending polyhedral particles of different shapes with the appropriate stoichiometry.