Ionic Conductivity in Solvent-Swollen Surfactant-Like Multiblock Copolymer Thin Films

Previously, bulk samples of multiblock copolymers consisting of alkyl blocks of a fixed length (x) strictly alternating with polar blocks containing lithium sulfonate groups (PESxLi) form layered morphologies at room temperature. Selectively swelling the polar domains of these multiblock copolymers with DMSO increased the ionic conductivity by 10^4 while maintaining the layered morphology in the bulk. To reduce the role of morphological defects (i.e. grain boundaries) on the conductivity measurements, this study fabricates well-aligned thin films by spin coating and uses interdigitated electrodes to measure Li conductivity. Thin films of PESxLi spontaneously form layered morphologies aligned parallel to the substrate, such that the interdigitated electrodes measure the in-plane conductivity. We report on our progress towards measuring the conductivity of solvent swollen, aligned layers of PESxLi thin films. Custom fabricated solvent chambers permit both grazing incidence X-ray scattering and electrochemical impedance spectroscopy measurements under controlled solvent vapor environments at temperature. These experiments facilitate direct comparisons to all atom molecular dynamics simulations and promise to improve the understanding of how solvent impacts ionic conductivity in nanostructured single-ion conducting polymers.