Stretchable and Electrochromic PDMS/PEDOT:PSS/P3MT Composite Films

Electrochromism refers to a phenomenon in which the color of a material is reversibly changed by electrochemical redox reaction depending on the switching of an applied voltage. Over inorganic materials such as metal oxides, conjugated polymers such as poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has various advantages such as high coloration efficiency and fast response speed. PEDOT:PSS is a representative conductive polymer with electrochromic ability that changes from light blue at oxidation (bleached state) to dark blue at reduction (colored state). However, since the fracture strain of pristine PEDOT:PSS film is only about 5%, there is limited limitation in applying pristine PEDOT:PSS film to soft electronics such as wearable devices, smart textiles, and implantable devices that require the stretchability of the materials. This study aimed to develop a stretchable and electrochromic electrode using PEDOT:PSS by blending PEDOT:PSS with poly(dimethylsiloxane) (PDMS) into polymer thin film. Morphological and chemical characterization by SEM and EDS analysis confirmed that PEDOT:PSS formed a honeycomb-like skeleton structure in which PDMS particles were distributed, forming conductive path that can dynamically withstand stretching. Furthermore, it was demonstrated that for different coloring, additional electrochromic polymer layer such as poly(3-methylthiophene) (P3MT) (blue & red) or poly(2,5-dimethoxyaniline) (green & yellow) can be electro-polymerized on the PDMS/PEDOT:PSS composite film due to the honeycomb-like skeleton structure of PEDOT:PSS. Additional electrochromic layer also had a honeycomb-like structure, enabling to dynamically withstand stretching without any delamination. Finally, fabricated PDMS/PEDOT:PSS/P3MT composite film showed excellent electrochromic ability upon stretching. Detail forming mechanism of PEDOT:PSS honeycomb and PDMS particle structures will be presented at the conference including their optical, mechanical and electrochromic characteristics.