where ρ in is the salt concentration inside the polymer phase, maintaining the electroneutrality condition, and R pol is the effective polymer radius (V pol = 4/3πR 3 pol ). Note that our mean-field theory can be considered valid only close to the coil-to-globule equilibrium when the polymer chain forms a rather compact conformation. The further assumptions are that the fraction of charged monomers has to be low and the salt concentration relatively high, i.e., the neutral reference state is only slightly perturbed. A similar thermodynamic description has been recently developed for microgels, albeit a different procedure to find the thermodynamic equilibrium was employed. Salt-specific effects on weakly charged copolymers can be captured qualitatively by a simplified theory which treats the ion-specific and non-specific electrostatic contributions on a simple additive level, as demonstrated on PNIPAM copolymers. In contrast, the theory developed in this work includes the ion-specific and non-specific interactions in a self-consistent way.