Can solvation free energy rationalize the phase behavior of ion-doped copolymers?

Previous experimental studies have established the pronounced effects of salt-doping on the morphological behavior of copolymers. The ionic solvation free energy has been recognized as an important factor for this doping effects, which has been encapsulated into an effective χ parameter that scales linearly with salt concentration. However, no general agreement between experimental and theoretial phase diagrams has been reached. By employing a recently developed ‘free’ ion model for salt-doped copolymers and cultivating the rich experimental data in literature, we show that, for two different molecular weights and over a range of compositions, the morphological varications can be captured by the solvation free energy alone, if the solvation radius is treated as an adjustable parameters.