Theory, simulations and applications for nanostructured polymeric materials

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This research proposal focuses on technologically important problems involving two classes of structured polymers, specifically block copolymers and polymeric brushes. While ordinary polymers are synthesized by joining together identical monomer units to form long-chain molecules, block copolymers consist of sections (or blocks) made from different monomers. The natural tendency for chemically distinct blocks to separate causes these molecules to self-assemble into various and often elaborate structures (or morphologies) with nanometer-sized domains. The ability to combine polymers with different characteristics into well-ordered nanostructures provides a powerful way of controlling material properties. As part of the Center for Sustainable Polymers (CSP), we will use this control to improve the properties of renewable plant-based polymeric materials in hopes they will compete or even outperform conventional petroleum-based materials. Furthermore, the self-assembly of block copolymers into nano-sized structures leads to many useful applications in nanotechnology. For instance, we are interested in the development of nano-sized vesicles for drug delivery, efficient methods for patterning surfaces on the nanoscale, and smart environmentally-responsive nanostructures. Polymeric brushes represent another class of structured polymers with many sophisticated applications in nanotechnology. They are formed by attaching polymers to a surface by their ends at a sufficiently high density that the crowding causes the polymers to stretch away from the surface. We will study charged polyelectrolyte brushes controlled by an external electric field for applications such as nano-sized actuators and gating nano-sized pores through thin membranes.*** *** To study these systems, my group will continue our development of self-consistent field theory (SCFT), for which I am regarded as one of the world's leading experts. SCFT permits exact mean-field calculations for structured polymers using coarse-grained microscopic models. It is a tremendous improvement over previous approaches and has been rewarded by a series of remarkable successes. The theory has been able to model very subtle effects, predict behaviour later to be confirmed by experiment, correct major experimental errors, and play a vital role in experimental studies. Because of its microscopic nature, SCFT is highly predictive and allows access to many quantities that experiments cannot measure. As a result, SCFT routinely provides simple intuitive explanations for its predictions. Despite its amazing track record with ordered structures, SCFT becomes inaccurate for fluctuating disordered morphologies. However, techniques for incorporating these fluctuations into SCFT are now emerging with the advent of field theoretic simulations (FTS), and we will continue our work on a promising Monte Carlo variant (MC-FTS).**