Tuning the Mechanical and Electrical Properties of Stretchable PEDOT:PSS/Ionic Liquid Conductors

Conducting polymers (CPs) constitute a promising building block to establish next-generation stretchable electronics. However, achieving CPs with both high electrical conductivity and outstanding mechanical stretchability beyond flexibility is still a major challenge. Therefore, understanding the key factors controlling such characteristics of CPs is required. Herein, a method to simultaneously manipulate the mechanical and electrical properties of a representative CP, PEDOT:PSS, by modifying ionic liquid (IL) additives is reported. The cation/anion modification of ILs distinctly improves the electrical conductivity of PEDOT:PSS up to approximate to 1075 S cm(-1), and the PEDOT:PSS/IL films showing higher conductivity also exhibit superior electromechanical stretchability, enabling them to maintain their initial conductivity under a tensile strain of 80%. Based on grazing incidence wide angle X-ray scattering and Fourier transform infrared spectroscopy analyses, it is found that the cation/anion-modified ILs control the crystallinity and pi-pi stacking density of conjugated PEDOT chains and the growth of amorphous PSS domains via IL-induced phase separation between PEDOT and PSS, which can be the origin of the significant conductivity and stretchability improvements in PEDOT:PSS/IL composites. This study provides guidance to develop highly stretchable CP-based conductors/electrodes.