The Influence of Side Chain Modifications on Transport in Polymeric Mixed Ionic/Electronic Conductors

Abstract

Mixed ionic/electronic conducting polymers (MIECs) are an important emerging class of materials, with rising interest due to the wide range of applications enabled by their unique properties. Recent research efforts have begun to focus on developing homopolymer-based MIECs by introducing ion-conducting side chains in place of alkyl chains that are more traditional for conjugated polymers. It has been widely shown that side chain variations in conjugated polymers have a significant effect on polymer electronic conduction; however, understanding of the influence of side chain variation for MIEC polymers on both the ionic and electronic conduction for MIECs remains limited, and optimization efforts have been largely Edisonian. This work seeks to expand on the field’s understanding of these MIEC materials and the interplay between side chains and ionic conduction, focusing on enabling predictive understanding of their material properties. First, we explore, the influence of the connection for an oligoethylene glycol side chain, either with an oxygen atom directly attached to the polymer backbone, or with a methylene bridge, highlighting the importance of proximity of the oxygen atom to the polymer backbone on ionic conductivity. We follow this with an investigation into varying the concentration and position of oxygen atoms of an oligoethylene glycol side chain, highlighting the influence that subtle changes in oxygen atom placement have on the polymer morphology, and polymer interactions with lithium salts.