Electrochromic Switching of the Optical Properties of Polyisothianaphthene

We present a detailed study of the electrochromic switching phenomena in the novel conducting polymer, polyisothianaphthene. We find reversible electrochromic switching with a characteristic switching time of a few hundred milliseconds. Since the results indicate that the rate limiting step in the electrochromic switching involves diffusion of the dopant species into the bulk of the polymer, we present a series of electron micrographs which provide an initial characterization of the morphology of PITN. The observation of a very open honeycomb‐like structure with morphological subunits on the 20Å scale is consistent with the relatively rapid doping kinetics and the associated electrochromism of PITN. Our conclusion is that the detailed morphology plays a critical role in determining the electrochromic switching; by controlling the morphology so as to minimize dopant diffusion distance in conductive polymers, it should be possible to achieve sufficient speed to be of interest for a variety of technological applications.