(121f) Influence of Backbone Solvation on Polyelectrolyte Solution Transport Properties

Nonaqueous polyelectrolyte solutions have recently been proposed as potential battery electrolytes due to the unique ability to tune the mobility of the anion relative to that of the electrochemically active lithium ion. This could potentially be used to study the effect of concentration polarization during charge, a major limiting factor in achieving fast charge rates that is caused by high anion mobility. An important consideration in the design of polyelectrolyte solutions for battery applications is the solubility of the polymer in battery – relevant carbonate blend solvents. We have recently demonstrated that polymers may be fully soluble in these solvents, even if the appended ion pairs are poorly dissociated. At the same time, it is common for a polyelectrolyte to be soluble in water, even if the neutral backbone polymer would not otherwise be soluble, for example polystyrene and its sulfonated derivative. It is thus important to understand the influence of backbone solvation versus solvation of the ions on the transport properties of these solutions, particularly for shorter chain polymers that may not follow theories for ideal infinite chains. Using a model polysulfone – based system, we investigate the conductivity, viscosity, and diffusion of polyelectrolyte solutions over a range of concentrations and molecular weights in dimethylsulfoxide (DMSO) and water. Sulfonated polysulfone is readily soluble and the charge group is known to dissociate in both solvents, but the neutral backbone polymer is only soluble in DMSO. We find marked differences in the transport behavior within the two solvents, particularly past the entanglement concentration. This study sheds light on the important parameters for polyelectrolyte solution design in different solvents.