Ionic Conductivity Enhancements in Solvent-Swollen Multiblock Copolymer Thin Films

Prior investigations incorporated ethylene carbonate into bulk samples of a multiblock copolymer consisting of alkyl blocks of precisely 12 carbons alternating with polar blocks containing lithium sulfonate groups (PES12Li). Experimental results on bulk samples found that the room temperature layered morphology was maintained upon selective swelling and resulted in a several order of magnitude enhancement in ionic conductivity. All-atom molecular dynamics simulations on this system revealed that most Li transport occurred at the polymer-solvent interface. To further investigate the role of solvent, this study fabricates well-aligned thin films by spin coating and uses interdigitated electrodes to measure Li conductivity. Upon swelling with solvent vapor, thin films of PES12Li retain parallel alignment, enabling measurement of the in-plane conductivity. Custom fabricated solvent chambers permit grazing incidence X-ray scattering, X-ray reflectivity, and broadband dielectric spectroscopy measurements under controlled solvent vapor environments at temperature. This report highlights our progress on the exploration of conductivity enhancements by incorporating selective solvents. These experiments facilitate direct comparisons to all-atom molecular dynamics simulations and improve the understanding of how solvent impacts ionic conductivity in nanostructured single-ion conducting polymers.