(397f) Sequestering Small Moleculues in Polyelectrolyte Complex Coacervates

The strong association of oppositely charged polyelectrolytes in solution can lead to a liquid-liquid phase separation known as complex coacervation. This process leads to a dense, polymer rich phase with a different environment than the water rich phase in terms of hydrophobicity, dielectric constant, and so on. Bassed on these differences, small molecules present in the solution will partition selectively based on factors such as hydrophobicity, charge, ability to form hydrogen bonds or other types of secondary interactions. Complex coacervation is able to sequester high amounts of contaminants present in aqueous solution, including such molecules as pharmaceuticals or other compounds that exist more and more frequently in wastewater streams and are difficult to remove. In this work, it is shown that both electrostatically bonded complex coacervates as well as hydrogen bonded ones can be used to control the sequestration of small molecules based on relative interactions between the small molecules, water, and the polyelectrolytes. The small molecules investigated in this work include both dyes and compounds such as antibiotics. The ability to sequester these small molecules is shown over a range of pH values, small molecule concentration, and salt concentration as well. We show that secondary interactions are much more effective at sequerstering small molecules than are electrostatic interactions, which interfere with the formation of the coacervate. This work has implications for water treatment as well as for chemical microreactors, where one might imagine concentrating reagents in solution in order to enhance reactivities.