Electron and ion transport in semi-dilute conjugated polyelectrolytes: view from a coarse-grained tight binding model†

Conjugated polyelectrolytes (CPEs) are a rising class of organic mixed ionic-electronic conductors, with applications in bio-interfacing electronics and energy harvesting and storage devices. Here, we employ a quantum mechanically informed coarse-grained model coupled with semiclassical rate theory to generate a first view of semidilute CPE morphologies and their corresponding ionic and electronic transport properties. We observe that the poor solvent quality of CPE backbones drives the formation of electrostatically repulsive fibers capable of forming percolating networks at semi-dilute concentrations. The thickness of the fibers and the degree of intrafiber connectivity are found to strongly influence electronic transport. Calculated structure factors reveal that fiber formation alters the position and scaling of the inter-chain PE peak relative to good solvent predictions and induces a narrower distribution of interchain spacings. We also observe that electrostatic interactions play a significant role in determining CPE morphology, but have only a small impact on the local site energetics. This work presents a significant step forward in the ability to predict CPE morphology and ion-electron transport properties, and provides insights into how morphology influences electronic and ionic transport in conjugated materials.