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Side Chain Engineering Control of Mixed Conduction in Oligoethylene Glycol-Substituted Polythiophenes



Jonathan Onorato, Zhongyang Wang, Yangyang Sun, Christian Nowak, Ban Dong, Lucas Flagg, Ruipeng Li, Lee J. Richter, Fernando Escobedo, Paul Nealey, Shrayesh Patel, Christine Luscombe


A major limitation for polymeric mixed ionic/electronic conductors (MIECs) is the trade-off between ionic and electronic conductivity; changes made that improve one typically hinder the other. In order to address this fundamental problem, this work provides insight into ways that we could improve one type of conduction without hindering the other. We investigated a common oligoethylene glycol side chain polymer by adjusting the oxygen atom content and position, providing structural insights for materials that better balanced the two conduction pathways. The investigated polymer series showed the prototypical conflict between ionic and electronic conduction for oxygen atom content, with increasing oxygen atom content increasing ionic conductivity, but decreasing electronic conductivity; however, by increasing the oxygen atom distance from the polymer backbone, both ionic and electronic conductivity could be improved. Following these rules, we show that, poly(3-(methoxyethoxybutyl)thiophene), when blended with lithium bistrifluoromethanesulfonimide (LiTFSI), matches the ionic conductivity of a comparable MIEC [poly(3-(methoxyethoxyethoxymethyl)thiophene)], while simultaneously showing higher electronic conductivity, highlighting the potential of this design strategy. We also provide strategies for tuning the MIEC performance to fit a desired application, depending on if electronic, ionic, or balanced conduction is most important. These results have implications beyond just polythiophene-based MIECs, as these strategies for balancing backbone crystallization and coordinating group interconnectivity apply for all semicrystalline conjugated polymers.
Journal of Materials Chemistry A


polymer, thin film, ionic transport' electronic transport, structure, X-ray diffraction


Onorato, J. , Wang, Z. , Sun, Y. , Nowak, C. , Dong, B. , Flagg, L. , Li, R. , Richter, L. , Escobedo, F. , Nealey, P. , Patel, S. and Luscombe, C. (2021), Side Chain Engineering Control of Mixed Conduction in Oligoethylene Glycol-Substituted Polythiophenes, Journal of Materials Chemistry A, [online],, (Accessed March 4, 2024)
Created August 31, 2021, Updated April 11, 2023