Propylene and butylene glycol: new alternatives to ethylene glycol in conjugated polymers for bioelectronic applications

Abstract
To date, many of the high-performance conjugated polymers employed as OECT channel materials make use of ethylene glycol (EG) chains to confer the materials with mixed ionic-electronic conduction properties, with limited emphasis placed on alternative hydrophilic moieties. While a degree of hydrophilicity is required to facilitate some ionic conduction in hydrated channels, an excess results in excessive swelling, with potentially detrimental effects on charge transport. This is therefore a subtle balance that must be optimised to maximise electrical performance. Herein a series of polymers based on a bithiophene–thienothiophene conjugated backbone was synthesised and the conventional EG chains substituted by their propylene and butylene counterparts. Specifically, the use of propylene and butylene chains was found to afford polymers with a more hydrophobic character, thereby reducing excessive water uptake during OECT operation and in turn significantly boosting the polymers’ electronic charge carrier mobility. Despite the polymers’ lower water uptake, the newly developed oligoether chains retained sufficiently high degrees of hydrophilicity to enable bulk volumetric doping, ultimately resulting in the development of polymers with superior OECT performance.

Citation
Moser, M., Wang, Y., Hidalgo, T. C., Liao, H., Yu, Y., Chen, J., … Yue, W. (2022). Propylene and butylene glycol: new alternatives to ethylene glycol in conjugated polymers for bioelectronic applications. Materials Horizons. doi:10.1039/d1mh01889b

Acknowledgements
The authors acknowledge financial support from KAUST, including Office of Sponsored Research (OSR) awards no. OSR-2018-CRG/CCF-3079, OSR-2019-CRG8-4086 and OSR-2018-CRG7-3749. The authors acknowledge funding from National Research Foundation of China (21875291 and 21702240) and China Postdoctoral Foundation (Grant No. 2021M693580) for the financial support, ERC Synergy Grant SC2 (610115), the European Union's Horizon 2020 research and innovation program under grant agreement no. 952911, project BOOSTER and grant agreement no. 862474, project RoLAFLEX, as well as EPSRC Project EP/T026219/1.

Publisher
Royal Society of Chemistry (RSC)

Journal
Materials Horizons

DOI
10.1039/d1mh01889b

PubMed ID
34935815

Additional Links
http://xlink.rsc.org/?DOI=D1MH01889B

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