Structure, Energetics and Phase Behavior in Polyelectrolyte-Colloid Systems

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The interactions between polyelectrolytes and small oppositely charged colloids are manifested in some important biological and technological phenomena. In order to rationalize these observations and current theory, experiments on well-defined model systems are essential. Such experiments will be carried out on polyelectrolytes in combination with three classes of well-defined synthetic colloid particles - mixed micelles, dendrimers, and carboxylated Ficoll fractions - and also with proteins. Polymer MW, linear charge density and chain stiffness will be varied systemically, along with colloid size and charge. A wide range of techniques, including turbidimetry and total intensity, electrophoretic light scattering, QELS, fluorescence recovery after photobleaching, SANS, time-resolved fluorescence spectroscopy and rheology will be used to answer questions about the energetics of interaction, the structure of soluble complexes, and phase behavior.%%%In addition to addressing fundamental questions and linking theory with experiment, the work will be of relevance to problems in (1) chemical technology, (2) cell biology, and (3) environmental issues, as follows. (1) Polyelectrolyte-colloid interactions are central to stabilization and flocculation in: water treatment, paper-making, and preceramics. (2) Non-specific polyion-protein association may be an important phenomenon controlling the role of proteoglycans in the extracellular matrix. (3) Complexes between polyelectolytes and micelles adsorbed on sand/soil may serve as barriers in the aquiferous migration of apolar pollutants. Students involved in this work will be exposed to a highly multidisciplinary approach that spans theory and applications.