The Importance of Organic Mixed Ionic-Electronic Conductor (OMIEC)–Water Interactions: A Perspective

Organic mixed ionic-electronic conductors (OMIECs) are an emerging class of materials with the potential to enable next-generation bioelectronic and energy technologies. Beyond their impressive capacitance, transconductance, and rate capabilities, OMIECs offer flexibility, easy processability, and the advantages of being composed of earth-abundant elements. Despite rapid progress in their development, a critical question persists: how do OMIECs interact with water, and how do their interactions with water impact their function? In this perspective, we explore the critical and complex role of water in determining OMIEC structure, charge transport properties, and electrochemical performance. We discuss how water's presence influences swelling, ion solvation, dielectric properties, and redox behavior, often in ways that depart from traditional redox-active polymer design rules. We provide an overview of emerging experimental and computational tools for deconvoluting these interactions. Finally, we argue for a shift toward well-defined model systems with controlled chemistries to probe hydration effects systematically. Bridging these foundational knowledge gaps will enable continued rapid progress in developing OMIECs for real-world applications.