Ion transport in polymer/ionic liquid films

Solid state-polymer electrolytes with high ionic conductivities are the subject of extensive research for a wide variety of electrochemical applications that include batteries, fuel cells, solar cells, super capacitors and actuators. However, the use of traditional polymer electrolytes is limited due to their reliance on volatile solvents for ion dissociation. The use of non-volatile organic solvents known as ionic liquids (ILs) in polymer electrolytes has recently been explored to overcome this limitation, but fundamental insights regarding the factors that affect ion conductivity in polymer/IL systems are missing. Ionic liquids are intriguing solvents due to their negligible vapor pressures, high ionic conductivities, wide electrochemical windows, and excellent chemical stability. In this work, we focus on the solid-state properties of polymer/IL mixtures and their potential impact to solid-state energy devices. Neutral homopolymer/IL mixtures and charged homopolymer (imidazolium-based polymerized IL)/ionic liquid mixtures were prepared to study the effect of compatibility and glass transition temperature on ion transport. Also, neutral diblock copolymer/ionic liquid mixtures were used to study the effect of IL content on nanoscale morphology and its subsequent impact on ion transport. In addition, the transport and mechanical properties of an actuator were investigated using a new experimental technique that was developed specifically for this purpose. The experiment uses time-resolved FTIR-ATR spectroscopy to study ion diffusion on a molecular level in a polymer/IL actuator when it was subject to an external electric field, while simultaneously measuring polymer strain using a real-time imaging.