Side chain engineering control of mixed conduction in oligoethylene glycol-substituted polythiophenes
Christine Luscombe a
a Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Japan
Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)
#OMIECs22. Organic mixed-ionic-electronic conductors and their application in Emerging Technologies
Online, Spain, 2022 March 7th - 11th
Organizers: Aristide Gumyusenge and Alexander Giovannitti
Invited Speaker, Christine Luscombe, presentation 129
DOI: https://doi.org/10.29363/nanoge.nsm.2022.129
Publication date: 7th February 2022

A 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, 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.

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