Engineering the Entropic Bond

Colloquium | January 31 | 4-6 p.m. | 180 Tan Hall

 Sharon Glotzer, University of Michigan

 Department of Chemical Engineering

Entropy, information, and order are important concepts in many fields, relevant for materials to machines, for biology to econophysics. Entropy is typically associated with disorder; yet, the counterintuitive notion that a thermodynamic system of hard particles might - due solely to entropy - spontaneously assemble from a fluid phase into an ordered crystal was first predicted in the mid-20th century. First predicted for rods, and then spheres, the ordering of colloids by entropy maximization upon crowding is now well established. In recent years, surprising discoveries of ordered entropic colloidal crystals of extraordinary structural complexity have been predicted by computer simulation and observed in the laboratory. These findings, which we present in this talk, demonstrate that entropy alone can produce order and complexity beyond that previously imagined, and that, in situations where other interactions are also present, the role of entropy in producing order may be underestimated. We quantify shape entropy in the self-assembly of colloidal systems, from nanoparticles to proteins, discuss the notion of the entropic bond in the context of traditional chemical bonds, and show how the entropic bond may be precisely engineered despite its statistical, emergent nature.