PEO - poly(ethylene oxide) - is a crystalline, water-soluble polyether whose chain of repeated ethylene oxide units coordinates cations along its backbone [1]. This solvating ability made PEO-LiX complexes the archetypal polymeric solid electrolyte, with ionic transport mapped early [1]. Ion specificity in PEO-NH4I and PEO-KBr composite electrolytes correlates salt identity with structure and conductivity [2]. Pegylated graphene oxide raises the performance of a PEO/polyvinyl alcohol blend solid electrolyte [3]. Triblock PEO-PPO-PEO copolymers associate in aqueous solution into micelles, with the association process explained across compositions [4]. Coarse-graining the same copolymers with the MARTINI force field brings their self-assembly into simulation reach [5].