(689a) Thermodynamics of Charging in Weak Polyelectrolytes

Applications in water desalination, drug delivery, and the design of microstructured functional materials involve extensive use of charged polymers. In particular, there has been significant interest in "smart" materials, comprised of weak polyelectrolytes, which are responsive to environmental pH and salt content, and take advantage of these conditions to preferentially separate solutes or release therapeutic payload. When dendritic polymers, polymer brushes, or condensed phases are present, the local structure and charging state exert enormous influence over the system's thermodynamics. Motivated by recent experiments demonstrating unexpected charging behaviors in weak polyelectrolyte brushes and functionalized membranes, we utilize Molecular Dynamics simulations coupled with Grand Canonical Reaction Ensemble Sampling methods to investigate the subtle interplay between salt concentration, pH, and associative interactions that control polymer microstructures. In particular, we are able to elucidate significant pKa shifting effects induced by polymeric topology and confinement. Importantly, we will discuss the consequences of these findings in the formation of associative phases, material uptake in polyelectrolytes and the effective operating ranges of smart materials.