Highly stretchable and aqueous solution-stable poly(3,4-ethylenedioxythiophene) doped with elastomeric sulfonated-SEBS

Abstract

The field of wearable and implantable bioelectronics is rapidly emerging for biological sensing, medical monitoring and treatment. Among the conducting polymers, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) stands out as a widely studied and commercially available material extensively employed in flexible bioelectronic applications. Nonetheless, PEDOT:PSS exhibits restricted stretchability, typically withstanding less than 10% strain, and its stability in aqueous environments is also limited. Furthermore, PSS is hygroscopic and acidic which, may contribute to the deterioration of electronic devices. Here we report on novel stretchable PEDOT-based electrodes, where PSS is replaced with a highly elastomeric, macromolecular dopant. Specifically, sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (sSEBS) was used as a co-dopant to PEDOT in a chemical oxidative polymerisation of PEDOT with various ratios of sSEBS:EDOT. Successful sulfonation of SEBS and synthesis of PEDOT:sSEBS composites were confirmed by means of FTIR and Raman spectroscopy. PEDOT:sSEBS composites were processed into dispersions in chloroform and characterised by dynamic light scattering. The free-standing films of PEDOT:sSEBS were prepared and investigated for their mechanical properties and in situ resistance. The optimised mass ratio of PEDOT:sSEBS (1 : 2 mass : mass) produced films that were highly stable in aqueous solutions, with a conductivity of 0.15 ± 0.03 S cm⁻¹ and stretchability of greater than 100% elongation at break. Electromyography (EMG) using the fabricated films demonstrated an application of the PEDOT:sSEBS films in wearable bioelectronics. The produced PEDOT:sSEBS films overcome some of the important deficiencies of extensively utilised PEDOT:PSS.