We notice that we obtain this precise fitting when considering N seg ≈ 1.9 × 10 6 segments for the experimentally determined N mon ≈ 10 10 number of monomers. Within the underlying Flory-Rehner theory, the number of segments N seg is not necessarily equal to the number of chemical monomers N mon or to the number of structural units -in case of considering Kuhn segments-. The equality only holds if the volumes of a molecule of solvent and a molecule of monomer are identical. Considering that we are assuming freely jointed chains, every structural segment accounts for a few chemical monomers, leading to a large volume difference between the solvent molecule and the one related to the structural segment. This justifies the difference between assumed N seg in the context of mixing and N mon . Keeping all the fitting parameters constant and equal to those for the lowest salt concentration, we compare the ionization and swelling for systems with higher salt concentrations.