Solvation and Dilution Thermodynamics in Ion-Containing Block Copolymers: a Numerical SCFT Study

Understanding the thermodynamics of ion-containing block copolymers is crucial for engineering the morphology of polymer electrolytes. We present a minimal model for the electrostatic interaction in these materials. Ion solvation energy and dielectric heterogeneity are treated explicitly, and the assumption that ions are bound to the conductive species is discarded. A symmetry-adapted solver for Poisson's equation is developed, enabling efficient exploration of parameter space and accurate resolution of bicontinuous morphologies. Complete phase diagrams are provided for varying salt concentrations and average dielectric permittivity. The resulting trends cannot be rationalized by an effective χ parameter. Two distinct regimes are identified, one dominated by ionic solvation effects and another by the translational entropy of ions. Canonical solid polymer electrolytes, such as PS-PEO/LiTFSI, appear to be in the solvation regime.