For example, most of the pioneering studies on polymer electrolytes are based on polyethylene oxide (PEO) complexed with alkali metal salts. Ionic liquids have been either mixed into neutral polymer bases or polymerized into poly(ionic liquid)s (PILs) for engineering various electrochemical devices. Ionic polymer metal composites (IPMC) consisting of a polyelectrolyte membrane placed in between two noble metal electrodes have been studied to enable large actuation under an applied electric field. Continued effort has been made to both develop novel ionically conductive polymers and understand fundamental ion conducting mechanisms to enable rational design based on application functional requirements.