All Donor Electrochromic Polymers Tunable across the Visible Spectrum via Random Copolymerization

A series of conjugated, random terpolymers based on all donor repeat units are prepared via direct (hetero)arylation polymerization yielding cathodically colored electrochromic polymers that span the visible spectrum. The polymers are based on repeat units of a dialkylthiophene, a 3,4-propylenedioxythiophene, and dimers of 3,4-ethylenedioxythiophene. Using a tight feedback loop between computational and experimental chemistry, the colors of these polymers are controllably tuned to cover the visible spectrum by controlling the monomer ratios. Examinations via ultraviolet-visible-near-infrared spectroscopy, differential pulse voltammetry, spectroelectrochemistry, and colorimetry show that, while these systems can vary greatly in their spectral properties, their oxidation potentials are all low (<0.5 V vs Ag/AgCl). The color tunability allows for access to neutral state orange, red, pink, magenta, purple, and blue polymers of various hues with a* values ranging from 22 to 35 and b* values ranging from -44 to 45, while maintaining highly transmissive oxidized states. This approach allows access to a wide gamut of colors with only three monomers while affording materials with low oxidation potentials and high contrast.