Effect of solvent-counterion interactions on polyelectrolyte solution properties

Polyelectrolytes are used as industrial and commercial thickeners, as they are water-soluble and enhance viscosity [1], but are insoluble in many organic solvents, which limits their applicability in products such as hand sanitisers. Here, we study how counterion-solvent interactions influence the solubility of polyelectrolytes.

Phase maps in the Hansen solubility parameter space were made for different salts of CMC. The phase maps of tetramethylammonium CMC (TMACMC) and benzyltrimethylammonium CMC (PhTrMACMC) were found to be similar. In contrast, the soluble region of TEACMC encompasses more solvents with lower Hansen parameters than that of TMACMC. Conductivity measurements, combined with small angle x-ray scattering (SAXS) measurements in mixed solvent media are used to quantify the fraction of dissociated counterions (f). The Bjerrum length of the solvent correlates inversely with f, as expected by the Manning theory of counterion condensation. With the results we have gathered, a framework for the influence of counterion-solvent interaction on polyelectrolyte solubility can be constructed.



[1] Clasen, C. and Kulicke, W.M., 2001. Determination of viscoelastic and rheo-optical material functions of water-soluble cellulose derivatives. Progress in polymer science, 26(9), pp.1839-1919.