(137c) Mechanisms of Equilibration in Block Copolymer Micelles

Block copolymer micelles are of interest across a broad spectrum of applications, from delivery of therapeutic agents to enhancing the effectiveness of engine lubricants. The competition that dictates the equilibrium structure, between corona and core block stretching and interfacial tension, is well understood. However, in many cases the micelles produced are not at equilibrium, and the rate of equilibration can be remarkably slow. We will describe measurements of the three major mechanistic steps assumed to govern micelle relaxation: chain exchange, fragmentation, and fusion. Time-resolved small-angle neutron scattering provides unique access to chain exchange, while dynamic light scattering, small-angle X-ray scattering, and liquid-phase TEM are used to follow fragmentation/fusion. Implications for theoretical treatments of these processes will also be discussed, as well as the relevance to formation of particle phases in bulk block copolymers.