Short Biography of Mitchell A. Winnik (2010)
Mitch Winnik obtained his Ph.D. in organic chemistry at Columbia University in 1969 and spent a postdoctoral year at Caltech studying organic photochemistry. He joined the faculty at the University of Toronto in 1970 and received tenure as an organic chemist. On sabbatical in Bordeaux France, he realized that he was bored with what he had been doing and switched his interest to polymer chemistry. Beginning in the late 1970’s, he and his coworkers pioneered various applications of fluorescence spectroscopy to polymers, including the study of the cyclization of polymer molecules in solution and the study of polymer-polymer interfaces. Among the polymer systems his research group has examined are latex films, polymer blends, block copolymers, interpenetrating networks, and water-soluble polymers, particularly associative thickeners. His group also investigates various aspects of molecular self-assembly. In collaboration with his colleague Ian Manners (now moved to Bristol in the UK), he and his students study the unique features of the self-assembly of inorganic block copolymers, particularly polyferrocenylsilane. In 2006, he and his students began a collaboration with an ICP mass spectroscopy group in the area of metal-chelating polymer tags for early detection of leukemia. At about the same time, he began a research program with Professor Greg Scholes on polymer-quantum dot interactions. These three projects now represent the main activities of his research group.
In 1998, he was awarded the title University Professor, the University of Toronto’s highest award in recognition scholarly excellence. He is a Fellow of the Royal Society of Canada and is listed by the ISI Web of Science as a most highly cited author in the field of chemistry.
Block Copolymer Micelles as an Organizational Motif for Quantum Dots
IDEAS FOR A MODEL NANOSCALE LIGHT HARVESTING SYSTEM
Mitchell A. Winnik
Department of Chemistry, University of Toronto
mwinnik@chem.utoronto.ca
For several years, we have been interested in studying the interaction in solution of polymers with semiconductor nanocrystals (quantum dots, QDs). The polymers that we have chosen to study have functional pendant groups that can serve as surface ligands for the QDs. If the polymer is a block copolymer with ligand groups in the shorter block, the polymer will self assemble into “crew cut” micelles in a selective solvent in which the longer block is poorly soluble. These micelles can serve as an organizational motif for the QDs. There are many opportunities, which we are exploring, to manipulate the shape of the micelle-QD hybrids: spheres, vesicles, cylinders.
A second level of sophistication becomes possible if one incorporates a conjugated polymer such as poly(3-hexylthiophene) (P3HT) into the hybrids. In this way one can create colloidally stable species with QDs in the corona and the conjugated polymer in the core. We think of these structures as simplified nanoscale models for a light harvesting system such as that found in purple bacteria. On the left side of the Figure is a cartoon showing this type of organization for spherical micelles in which the QDs absorb light and then transfer the energy across the heterojunction to the P3HT incorporated into the micelle core. On the right side of the Figure is a TEM image of hybrid micelles formed from polystyrene-poly(4-vinylpyridine), P3HT and CdSe quantum dots.
The experiments I will describe in my seminar were carried out by two former students from Professor Xi Zhang’s laboratory, Dr. Mingfeng Wang and Mr. Meng Zhang.
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