Fast electrochromic polymers based on new poly(3,4-alkylenedioxythiophene) derivatives

A series of new poly(3,4-alkylenedioxythiophene)s were electrosynthesized using 3,4-alkylenedioxythiophene derivative monomers where either the size of the alkylenedioxy ring, or the nature of the pendant group, was varied. Optoelectrochemical experiments revealed that electronic band gaps for all polymers are approximately 1.7 eV(730 nm). These cathodically coloring polymers switch from a relatively transmissive light green in the oxidized form to an opaque dark blue in the reduced form. Multiple switching studies, monitoring the electrochromic contrast, showed that ca. 300 nm thick polymer films could be fully switched between their reduced and oxidized forms in 0.8–2.2 s with Δ%T of 44-63%. In situ conductivity studies carried out on relatively thick polymer films (2.7–9.5 μm) deposited between large gap (200 mm) lateral growth electrodes demonstrated the low potential turn on for these materials and relative maximum conductivities of 0.2–12.1 S/cm were attained.