45430-AC7
Optical Tracer Self Diffusion Studies of Polyelectrolytes at Low Salt
The primary project theme is improved understanding of the self-diffusion of fluorescently labeled polyelectrolyte probes in low-salt conditions, especially through matrix solutions of other polyelectrolytes that are identical, except for the absence of label. Polyelectrolytes are important for enhanced oil recovery operations. The primary tool of investigation is dialysis fluorescence photobleaching recovery, and the needed apparatus has undergone significant improvements to enhance the reliability and reproducibility of results. Although the fluorescence photobleaching recovery method is capable of using very small amounts of probe polymer isolated by analytical scale gel permeation chromatography after a synthesis involving addition of fluorescein isothiocyanate to free radical-polymerized allylamine-styrene sulfonate random copolymers, as described in the proposal, efforts have been directed towards a new atom transfer radical polymerization protocol. This should result in larger quantities of material, beneficial to our experiments but also of interest to the community at large. Additional studies have included, for the first time, a careful investigation of the partial specific volume of poly(styrene sulfonate) as a function of concentration and added salt. It was hoped that such an investigation might reveal bulk scale evidence of the elusive structures behind the "slow mode" phenomenon first seen in dynamic light scattering. Work is turning now to the risky part of this proposal, investigation of the dynamics of self diffusion of probe polyelectrolytes at high spatial frequencies.
