The Influence of Alkyl Spacers and Molecular Weight on the Charge Transport and Storage Properties of Oxy‐Bithiophene‐Based Conjugated Polymers
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- Department of Physics and Centre for Processable Electronics Imperial College London SW7 2AZ London United Kingdom
- Department of Chemistry University of Oxford OX1 2JD Oxford United Kingdom, Department of Materials Science and Engineering Stanford University 94305 Stanford CA United States
- Department of Engineering University of Cambridge CB3 0FA Cambridge United Kingdom
- Department of Materials Science and Engineering Stanford University 94305 Stanford CA United States
- Department of Biomedical Engineering Northwestern University 60208 Evanston IL United States
- Department of Chemistry University of Oxford OX1 2JD Oxford United Kingdom, Andlinger Center for Energy and the Environment Department of Electrical and Computer Engineering Princeton University 08544 Princeton NJ United States
Abstract Conjugated polymers (CPs) with polar side chains can conduct electronic and ionic charges simultaneously, making them promising for bioelectronics, electrocatalysis and energy storage. Recent work showed that adding alkyl spacers between CP backbones and polar side chains improved electronic charge carrier mobility, reduced swelling and enhanced stability, without compromising ion transport. However, how alkyl spacers impact polymer backbone conformation and, subsequently, electronic properties remain unclear. In this work, we design two oxy‐bithiophene‐based CP series, each featuring progressively extended alkyl spacer lengths and two distinct molecular weight (MW) distributions. Using operando characterisations, we evaluate the (spectro)electrochemical and swelling properties of the polymer thin films, and their performance in organic field‐effect transistors and organic electrochemical transistors. Surprisingly, alkyl spacers negatively impact the hole mobility of our polymers, with higher MW amplifying this effect. Using molecular dynamics simulations, we show that it is thermodynamically favourable for adjacent non‐polar alkyl spacers to aggregate in polar electrolytes, leading to backbone twisting. Further spectroscopic measurements corroborate this prediction. Our findings demonstrate the active interactions between side chain structure, MW and electrolyte/solvent polarity in influencing polymer performance, underscoring the importance of considering solvation environment effects on polymer conformation when designing new mixed conducting CPs for electrochemical applications.
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- SC0014664; AC02-76SF00515
- OSTI ID:
- 2483708
- Journal Information:
- Angewandte Chemie (International Edition), Journal Name: Angewandte Chemie (International Edition) Journal Issue: 6 Vol. 64; ISSN 1433-7851
- Publisher:
- Wiley Blackwell (John Wiley & Sons)Copyright Statement
- Country of Publication:
- Germany
- Language:
- English
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