(351a) Using Molecular Design Concepts and Light to Engineer Surface Properties

Surface modification strategies are an essential aspect of many important material applications and have become increasingly sophisticated. In many cases it is now desirable to control surface structure and functional group distribution at the nanoscale. The goal of our research is therefore to gain a fundamental understanding of the molecular-level design and fabrication of nanostructured functional surfaces on both soft and hard material substrates with particular emphasis on creating smart, responsive interphases. There are several challenges involved with the implementation of smart surface nanotechnology: one must have molecular design rules, one must have techniques for precise synthesis of functional organic and polymeric surface molecules, one must have some method to assemble these molecules at surfaces with controlled nanostructure, and finally, one must provide an energy source if the surface is to show responsive character. The first part of the presentation presents three rules that have emerged for the molecular design of functional polymer surfaces : surface segregation, surface structure and surface reorganization. The surface tension and surface structures for a number of model functional polymer systems will be reported to illustrate these principles. A lattice model is described that is found to provide excellent predictions of surface properties and structure under essentially all conditions, including surface reorganization. Several examples will be presented where the design principles have been successfully applied to develop design solutions for particular surface modification problems. These examples show that surface modification molecules can be designed and synthesized to spontaneously self-assemble at a substrate surface by simple adsorption form a solution in supercritical carbon dioxide. Finally, we show that preprogrammed, smart surfaces can be synthesized that change their properties upon illumination with light. Photochemical surface modification uses only photons as reagents and thus is highly controlled, clean, and amenable to spatial patterning. This new technique allows for surface chemical patterning by standard photolithographic masking techniques. ?Shedding light? on surfaces is shown to constitute an exciting new method for preventing the dewetting of polymer films, for creating carbohydrate antigen microarrays and for the general patterning of a variety of interesting biological molecules on virtually any surface.

Molecular Design of Functional Polymer Surfaces, J. T. Koberstein, J. Polym. Sci. Polym. Phys. Ed. 2004, 42, 2942-2956