Ion and Water Transport in Polyelectrolyte Membranes

Polyelectrolyte membranes play essential roles in advancing membrane-based sustainable technologies for energy, environment, food and health. To design next-generation membranes to address grand challenges of our time, understanding of ion and water transport in polyelectrolyte membranes is critical. Toward this goal, we designed a new library of weak polyelectrolyte membranes, i.e., acrylic acid–poly(ethylene glycol) diacrylate (AA-PEGDA) network with a wide ion-exchange capacity range (IEC = 0 – 4 mequiv/g) and limited water swelling. In this system, on the same chemical structure, the charged group concentration can be systematically varied (degree of ionization, α = 0 – 1) via controlling the external pH, without the need of changing the chemical structure of the polymer. Using this unique feature, we systematically studied the sorption and diffusion of ion and water in the polymers via multiscale characterization, with the goal of establishing the design principles of polyelectrolyte membranes. Our study will catalyze the design of new charged polymer membranes for broader membrane-based applications in sustainability.