N-substituted poly(3,4-propylenedioxypyrrole)s:: High gap and low redox potential switching electroactive and electrochromic polymers

A series of electrochromic N-substituted poly(3,4-propylenedioxypyrrole)s (PProDOPs) are reported, which exhibit the combined properties of a high (> 3. eV) electronic band gap, colored oxidatively doped forms, and easily accessible, low redox potentials. Utilizing methyl (Me), propyl (Pr), octyl (Oct), propanesulfonated (PrS), and ethoxyethoxyethanol (Gly) pendants, the absorbance of the pi-pi* transition of the resulting polymers is blue-shifted when compared to the nonderivatized parent. For example, in the case of poly(N-ethoxyethoxyethanol ProDOP) (N-Gly PProDOP), this transition displays a maximum at 306 nm (onset at 365 nm), providing a colorless and highly transparent neutral polymer with a luminous transmittance greater than 99% for a film thickness of about 200 nm. N-Substituted PProDOPs display very well-defined cyclic voltammograms, with E-1/2 < -0.1 V vs Fc/Fc(+) (+0.2 V vs SCE), negative of the oxidation of water, as desired for materials having stable doped forms and long-lived redox switching properties. In addition, the presence of a sulfonate group at the end of the propyl chain in N-PrS PProDOP offers the possibility of self-doping along with water solubility of the polymer. As a result, N-PrS PProDOP exhibits a fast and regular growth even in the absence of supporting electrolyte. This new family of polymers has not only shown interesting electrochromic properties in the visible. Upon doping, a very strong absorption is observed in the near-infrared (NIR) with changes in transmittance up to 97%, extending the use of these polymers as the active layer in vis-NIR switchable devices.