(452i) Reinforced Poly(ionic liquid) Ionogels for Ionic Electroactive Actuators

Poly(ionic liquids) (PILs) are a subclass of strong polymer electrolytes that incorporate ionic liquid (IL) groups onto a polymer backbone, resulting in polymers with many unique IL properties. In particular, these materials exhibit several favorable electrochemical and thermal properties due to their intrinsic ion conductivity, wide electrochemical windows, non-flammability, and high thermal stability, making them attractive materials for electrochemical applications. Recently, PILs have been considered as innovative pseudo-solid electrolytes in ionic electroactive polymers (IEAPs) systems. Under an applied electric potential, IEAPs can mechanically respond, or actuate, due to ion migration within a solid or gel polymer electrolyte layer sandwiched between two conductive electrodes. This polymer electrolyte layer is typically composed of a liquid electrolyte—either an aqueous salt solution or ionic liquids—encapsulated in a solid polymer matrix (e.g., Nafion or PVDF) to form ion conductive hydrogels or ionogels, respectively. PILs are highly compatible with ionic liquids, resulting in ionogels with minimal IL leakage and increased operational stability over time, making them ideal polymer matrices for ionogels-based actuators. However, more investigation is needed to improve their mechanical properties for optimal actuation behavior. One method to improve the mechanical behavior is incorporating reinforcement agents such as nanomaterials or fibers into the gel matrix. In this work, two imidazolium-based PIL polymers were synthesized and combined with a low melting point ionic liquid to form ionogels. A survey of select reinforcing agents, including cellulose-based filter paper, electrospun fibers, and graphene oxide, were also incorporated into the ionogels to improve mechanical properties and actuation behavior. FTIR spectroscopy was used to characterize the IL and reinforcing agent incorporation into the developed ionogels. DSC and TGA thermal characterization techniques were performed to determine polymer glass transition temperature and thermal stability. The ion conductivity of the ionogels was measured through EIS. The mechanical properties were also examined. Electroactive actuation behavior of the PIL-based ionogels at low voltages (<5V) was investigated for select ionogels sandwiched between two layers of electrode material.