Polystyrene-block-polyethylene-block-polystyrene (SES) copolymers were blended with homopolymer polystyrene (PS), and films of the blend were solvent cast using a doctor blade. The nonporous SES and PS films were exposed to both tetrahydrofuran (THF) and methanol (MeOH) in an alternating fashion for 1 min intervals three times, without letting the films dry between solvent immersions. At this point, either the films were removed from MeOH and dried or the films were immersed in THF and then dried. THF is a nonsolvent for crystalline polyethylene (PE) but a good solvent for both amorphous PE and PS. Methanol is a nonsolvent for semicrystalline PE, amorphous PE, and PS. Films that were dried with MeOH as the final nonsolvent were highly porous and exhibited high conductivity when swollen in a liquid electrolyte. In contrast, films that were dried with THF as the final nonsolvent were nonporous and exhibited poor conductivity when swollen in a liquid electrolyte. We study the fundamental effect of nonsolvent exposure on film properties using electron microscopy, nitrogen physisorption, and X-ray scattering techniques.