 | James. S. McDonnell Distinguished University Professor
Professor, School of Arts & Sciences, Department of Chemistry
Professor, School of Medicine, Department of Radiology
Faculty Member, Center for Materials Innovation
McMillen 509 Department of Chemistry
Washington University in St. Louis
St. Louis, MO 63130-4899 Phone: 314 935 7136 <br> Fax: 314 935 9844 |
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Editor, J. Polym. Sci., Part A: Polym. Chem., jpsa.wooley@wuchem.wustl.edu
Ph.D., Cornell University (1993)
B.S., Oregon State University (1988)
Washington University Distinguished Faculty Award (2005); NSF Division of Materials Research, Special Creativity Extension (2002); Arthur C. Cope Scholar Award in Organic Chemistry (2002); Academy of Science of Saint Louis Innovation Award (2002); Office of Naval Research Young Investigator Award (1998); Army Research Office Young Investigator Award (1996); DuPont Young Professor Grant (1996); National Science Foundation National Young Investigator Award (1994). |
ResearchOur research interests are focused broadly upon the design, synthesis and characterization of unique polymers, with emphasis upon the development of synthetic methodologies that allow for the preparation of complex nanostructured materials. Just as typical synthetic chemists prepare molecules of specific stereochemistry and connectivity, using natural products as the targets to exercise their craft, we are identifying nanoscopic natural products, e.g. viral capsids, lipoproteins, and even dolphin skin, as synthetic targets. We do not attempt, however, to synthesize exactly these structures, but rather, to produce synthetic materials that capture the basic structural and functional elements.
We rely upon a combination of supramolecular assembly and covalent chemical reactions, performed in an iterative sequence, to produce and manipulate such nanoscale structures. The preparation of complex nanostructured materials is being advanced rapidly with the development of a methodology that relies upon two fundamental techniques in polymer chemistry: (1) the phase segregation of incompatible block copolymers or polymer mixtures to produce well defined nanoscopic domains over long ranges; and (2) crosslinking within selective regions of those phase segregated assemblies to provide robust materials comprised of regions that exhibit contrasting chemical, physical and mechanical properties. Although the phase segregation of incompatible polymers is not a new phenomenon, the regioselective crosslinking of the segregated assemblies is only recently being realized as a versatile methodology by which to tune the size, shape and behaviour of materials.
Figure 1: Atomic force microscopy images the surface characteristics of the amphiphilic crosslinked network materials upon preparation and after incubation under artificial sea water (upper and lower panels, respectively). Inversion of the surface occurs due to conformational reorganization, which occurs upon swelling of the poly(ethylene glycol) rich domains. Each of these images illustrates the amphiphilic surface features, and serves as a measure of the nature of the phase segregated domains.
In one example, the preparation of non-fouling and foul-releasing surfaces is accomplished by the bulk-state phase segregation and covalent crosslinking of hyperbranched fluoropolymer and linear poly(ethylene glycol) mixtures. The nanostructured surface features in this case are dictated mainly by the stoichiometries of two components and the coating thickness, which is driven by compositional and topological differences. Detailed characterization of these surfaces, including interesting surface reorganization events for these materials, have been observed.
In a second example, the supramolecular assembly of amphiphilic block copolymers in water produces polymer micelles, which are then stabilized by crosslinking reactions that are limited to the shell layer. Detailed examination of the physical properties of these nanostructures and their subsequent physical and chemical manipulation is leading to a greater understanding of their structure and properties and is allowing for their development in areas as broad as drug delivery and molecular imaging.
Figure 2: The chemistry involved in the shell crosslinking of polymer micelles assembled from poly(acrylic acid)-b-(methyl acrylate) is shown in the upper panel. Atomic force microscopy allows for visualization of the two-dimensional arrays of nanoparticles, in which the particle heights and the interparticle spacings are dependent upon the extent to which the crosslinking chemistry is performed. |
