Post-polymerization functionalization of poly(3,4-ethylenedioxythiophene) films by 1-fluoro-2-nitro-4-azidobenzene: electrochromism and redox behavior

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) films electropolymerized from an aqueous micellar solution encompassing the monomer (EDOT) and dopant sodium bis(2-ethylhexyl) sulfosuccinate (AOT), have been functionalized after polymerizationvia a photochemical nitrene reaction using the reactive 1-fluoro-2-nitro-4-azidobenzene (FNAB), typically used for biochemical applications. Prior to polymer functionalization, the reaction of the monomer with FNAB was followed by Fourier transform infrared, absorption and light emission spectral studies. The functionalization of the polymer has been confirmed by characteristic FTIR absorptions and X-ray photoelectron spectroscopic signals due to –NH, C–F and –NO2groups of FNAB. The unusual surface morphology of the functionalized PEDOT–AOT film with micron sized outgrowths with a partially crystalline structure is responsible for its superior coloration efficiency (340 cm²C⁻¹ at 550 nm), higher charge storage capacity (0.7 mC cm^-2 at 5 mV s^-1), better electrochemical cycling stability (high optical contrast is retained even after 3000 clear to dark and dark to clear cycles) and faster switching kinetics as compared to the electrochemical response of the pristine PEDOT–AOT film. These results demonstrate the unparalleled potential this functionalizing methodology has for creating electroactive polymer films with unusual morphologies and electrochemical properties for electrochromic applications.