(355e) Impact of Solvation Energy on the Morphological Behavior of Ion-Containing Copolymers

The variation in morphological behavior of block copolymers doped with Lithium salt is widely reported, but is poorly understood. A minimal model for these ionic mixtures is presented, that resolves the spatial variation of dielectric permittivity explicitly and treats ions as unbound but readily solvated in high-permittivity domains. The theoretically predicted phase diagrams are compared to experimental data for PS-PEO copolymers doped with LiTFSI. Nearly quantitative agreements are obtained by introducing a single fitting parameter, the ionic solvation radius. The results reveal evidently that the departure from the neutral copolymer behavior cannot be rationalized by a single effective χ parameter, but can be rationalized by the solvation effects.