(6bv) Phase Transitions and Self-Assembly of Block Copolymers, Colloids and Proteins

Entropy maximization and the emergence of order from disorder are highly universal principles for the assembly of materials. Self-assembly allows the creation of novel, functional materials from nanoscale building blocks. We discuss how entropy controls the formation of structure in polymeric and colloidal materials. In block copolymers, the order-disorder transition isdriven by collective composition fluctuations, and we show how they stabiliz the disordered phase in a universal way. Computer simulations of various chemically distinct coarse-grained models of diblock copolymers show how their phase behavior can be mapped onto each other using a minimal set of parameters. In colloidal self-assembly, the depletion interaction mediates an emergent, attractive force between large colloids in a sea of smaller particle. We show how these forces introduce strong entropic bonds between faceted particles that favor the creation of open structures. Our results point towards novel ways of understanding the role of particle shape and entropy for structure formation also in biological systems. One intriguing yet poorly understood phenomenon is the crystallization and aggregation of folded proteins.