Intrinsically Stretchable Electrochromic Display by a Composite Film of Poly(3,4-ethylenedioxythiophene) and Polyurethane

A stretchable, electrochromic film of a uniform composite of poly­(3,4-ethylenedioxythiophene):<i>p</i>-toluene sulfonic acid (PEDOT:PTS) and polyurethane (PU) (PEDOT/PU) was fabricated, and its integration with a hydrogel as a free-standing, stretchable electrochromic (EC) display was demonstrated. The PEDOT/PU composite film was prepared by the spin coating of a solution containing an EDOT monomer and PU, followed by oxidative polymerization using iron­(III) tosylate at elevated temperature. The fabricated film showed reversible electrochromism without an external conductive support. The color change of the film can be used to quantify the progress of the redox reactions by means of digital camera image analysis and a custom mobile phone app