Development of completely sulfonated sodium polystyrene sulfonate and its dynamics in low-salt solutions

An investigation into the temporary aggregates that comprise the slow diffusive mode of polyelectrolyte solutions at low-salt was made through fluorescence photobleaching recovery measurements of sodium polystyrene sulfonate. Commercial sources of this important industrial material, invariably made by post-treatment of polystyrene, are not fully sulfonated. To address this issue a reproducible, gram-scale synthesis over a broad molecular weight range was done via aqueous atom transfer radical polymerization. Differences in the degree of sulfonation between commercial polymer and that made in-house were identified and quantifiable with FT-IR and NMR. Solution and bulk properties, including refractive index increments, polymer solution conformation, partial specific volume, and glass transition temperatures were substantially different. Direct and indirect evidence for temporary aggregates was not found using a long-distance fluorescence photobleaching recovery instrument to measure diffusion in single and mixed molecular weight systems, respectively. Instead, the diffusion of fluorescent probes was found to depend on unlabeled matrix correlation lengths. Construction of a holographic version of the instrument significantly increased the spatial frequency at which polymer diffusion could be probed and permitted the measurement of diffusion coefficients that were similar in magnitude to the slow mode observed by dynamic light scattering.Ph.D