A Fruitful Usage of a Dialkylthiophene Comonomer for Redox Stable Wide-Gap Cathodically Coloring Electrochromic Polymers

Abstract

A series of conjugated polymers are prepared via direct heteroarylation polymerization with the goal of yielding wide-gap, yellow and orange switching to transmissive cathodically coloring electrochromic polymers (ECPs). The polymers are based on repeat units of dialkylthiophene (DAT) in alternation with dioxythiophenes (DOTs) with various side chains to induce differing levels of inter-ring strain yielding 3,4-ethylenedioxythiophene (DAT-EDOT), 3,4-propylenedioxythiophene (DAT-ProDOT), 3,4-(1,3-dimethylpropylene)dioxythiophene (DAT-DMP), and 3,4-dimethoxythiophene (DAT-DMOT) structured polymers. Examination of the optoelectronic properties via UV–vis–NIR spectroscopy, differential pulse voltammetry, and spectroelectrochemistry shows that while increasing the inter-ring strain induced by the side chain of the DOT unit leads to an increased oxidation potential ranging from −122 to +288 mV relative to Fc/Fc+, this does not decrease the accessibility of the extreme charge states. Through subtle steric intera...