Cédric Plesse

Polymeric ionic liquids (PILs) are an emerging class of materials which have attracted considerable attention as solid‐state electrolytes because they combine the attractive properties of ionic liquids with the mechanical features of polymers. This paper presents a new method for the synthesis and characterization of stretchable and highly ionically conducting membranes and their subsequent use in truly all‐solid‐state, flexible, and soft electroactive devices. Linear conductive PIL and reinforcing poly(ethylene oxide) (PEO) network are first intimately entangled during the synthesis of a semi‐interpenetrating polymer network (semi‐IPN). Polymerization kinetics, thermomechanical properties, as well as ionic conductivity measurements reveal that for the 60:40 wt ratio of PEO:PIL a true synergy of the properties of both polymer partners is achieved, with ionic conductivities up to 8.7 × 10 −5 S cm −1 at 30 °C and elongations at break greater than 100%, being both superior to each partners taken separately. The performances of these semi‐IPNs as central membranes in all‐solid‐state electrochemical microdevices, composed of three self‐supported and flexible layers, namely poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/semi‐IPN membrane/PEDOT:PSS, are successfully demonstrated. Their testing as liquid‐free ionic actuators and liquid‐free piezoionic sensors undoubtfully proves that electromechanical and mechanoelectrical responses of these all‐solid‐state microdevices can reach performances identical to that of “classical” ionic liquid‐filled systems.