Dynamics of (Poly-)Ionic Liquids in an Ion Conductive Paper-Polymer Composite Monitored by Cross Relaxation Dynamic Nuclear Polarization

Abstract Paper-polymer composites (PPCs) are increasingly applied as sustainable ion-conducting membranes in modern energy storage systems. Their recycling, circularity, and optimization, however, require a more detailed understanding of local structures and dynamics at a molecular level influencing macroscopic properties such as stability and ion conduction. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has evolved into a powerful tool for studying paper and cellulosic materials, but its application to PPCs, particularly in membrane technology, is still limited. This study demonstrates the power of ssNMR spectroscopy combined with dynamic nuclear polarization (DNP) to investigate dynamics and interactions via selective signal enhancement in PPCs featuring ionic conductivity. The results reveal changes in molecular mobility after polymerization, allowing for distinguishing overlapping components with different mobilities.