Conducting polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), are very promising for organic electronics, performing as charge transport layers, flexible electrodes, resistive sensors, among others. However, for applications where the devices interface aqueous or humid environments (e.g. in bioelectronics), both high conductivity and water resistance are essential. In this communication, we introduce oxetanes as a novel class of additives that significantly enhance both the electrical conductivity and structural stability in water of PEDOT:PSS films.
We investigated the structural properties of oxetanes responsible for these enhancements. It was discovered that oxetanes undergo polymerization in the acidic medium of PEDOT:PSS, leading to the formation of polyether compounds [1]. Additionally, hydroxyl-substituted oxetanes can create covalent cross-links or hydrogen bond interactions with the negatively charged PSS. These interactions screen the electrostatic forces between PEDOT and PSS, reducing Coulombic interactions and promoting PEDOT segregation and structural rearrangements that enhance charge transport. We demonstrate that PEDOT:PSS ink formulations containing oxetanes, applied through spin-coating or inkjet printing, can produce highly conductive thin films on both rigid (glass) and flexible (PET) substrates. These films can serve as water-resistant electrodes in electronic devices, including photovoltaic cells [2] and electrochemical field-effect transistors operating with aqueous electrolytes [3]. In addition to thin films deposited on substrates, we successfully developed flexible, free-standing PEDOT:PSS films, with enhanced water resistance and conductivity, by incorporating an oxetane compound as an additive. The obtained flexible films demonstrated good potential as health-monitoring electrodes [4].


[1] S. M. Jorge, L. F. Santos, A. Galvão, J. Morgado, A. Charas, Adv. Mater. Interfaces, 8, 2100517 (2021).
[2] S. Silva, A. Ablú, F. Garrudo, A. Galvão, L. Santos, J. Morgado, A. Charas, Polymer, 282, 126196 (2023).
[3] C. Príncipe, S. Silva, M. Matos, L. Santos, J. Morgado, A. Charas, Org. Electron. 125(1), 106985 (2024).
[4] S. Silva, L. Santos, M. Ferreira, C. Marto-Costa, A. Serro, A. Galvão, J. Morgado, A. Charas, Polymers, 16(16), 2292 (2024)

Thanks to funding from Fundação para a Ciência e a Tecnologia (FCT) (Portugal) through Instituto de Telecomunicações (contract no. UIDB/50008/2020).