This award supports the research program of the Principal Investigator in the area of pattern formation in block copolymer systems. Block copolymers are molecular structures formed by bonding together two or more different polymers. Incompatibilities between different blocks lead to a variety of patterns and organization on nanoscopic scales, which in turn leads to a number of different material properties. This project builds and studies theoretical models for the assembly of block copolymers into a variety of microscopic architectures. This will lead in turn to the development of formulas that connect molecular properties of polymers to mechanical and morphological behaviors at a larger scale, which will allow prediction and engineering of new materials formed from patterned copolymer phases and aggregates. There are a number of nanoscale fabrication and biotechnological applications of this approach, including nanolithography, photonics, electronic storage systems, molecular-sized machines, controlled drug delivery, and synthetic biological structures. Defect evolution of bulk copolymer phases and orientational ordering is studied in the context of computations performed with reduced dimensional models for hexagonal and lamellar geometries. The effects of external fields will also be incorporated into this model-reduction framework. Copolymer aggregates such as micelles and vesicles will be studied using analytic techniques for stability and bifurcation, as well as large scale numerical simulation. Models for amphiphilic bilayers and heterogeneous membranes will also be constructed and analyzed in a similar framework. The project will broadly impact experimental investigations and the design of manufacturing processes, as well as provide educational opportunities for graduate and postdoctoral researchers.