In Fig. , we show the theoretical prediction of the ionization degree versus pH sys for the indicated c res salt . We notice that with increasing c res salt the curves shift towards lower pH-values, approaching the ideal Henderson-Hasselbalch behavior due to the suppression of the strong electrostatic repulsion between nearby monomers, as discussed earlier. Figure shows the swelling curves v/v max , relative to the largest swelling volume for the lowest salt concentration c res salt = 0.001 M, obtained with the theoretical models. We observe that for the case of a lower salt concentration, the theoretical agreement with the experiments is very good. However, we find an underestimation of swelling at high salt concentrations and large pH sys , consistent with the observations in Fig. .