Multi-scale characterization of polymeric mixed conductors

Polymeric mixed ion-electron conductors are emerging as key materials for a variety of electrochemical devices. The ability to transport both ions and electrons within a single material often requires an intricate and multiscale structure. Characterization of that structure remains a challenge. Our work has focused on electron microscopy, complemented by X-ray scattering, to reveal chain packing and mesoscale assembly of mixed conductors used in biodevices and biosensors. High resolution transmission electron microscopy reveals chain packing of PEDOT:PSS and similar polymer mixtures in solution and films that are dry or hydrated. This approach reveals how aggregates in solution lead to intricate microstructures in films, and how swelling affects the morphology. 3D reconstructions from electron tomography also reveal new aspects of the out-of-plane structure, including layering that can be perturbed through salt additives. Altogether, our work reveals how the multiscale structure impacts various dynamical properties, including the mechanical response and charge transport.