Probing Comonomer Selection Effects on Dioxythiophene-Based Aqueous-Compatible Polymers for Redox Applications

Oligoether-functionalized dioxythiophene polymers are a promising class of materials for electrochemical applications requiring aqueous electrolytes with rapid, reversible redox behavior, high pseudocapacitance, and strong electrochromic contrast. By copolymerizing different monomers (EDOT, DMP, and PheDOT) with an oligoether-functionalized propylenedioxythiophene unit, we tune the redox properties, modulating the onsets of oxidation, redox kinetics, and conductance properties in an aqueous electrolyte (NaCl/H₂O). Density functional theory calculations are subsequently employed to establish a theoretical basis for the observed differences in energy levels of the polymers. Polymer films demonstrate <1 s discharge rates, <1.5 s electrochromic switching times, and 90% charge retention after 1000 cycles. As these materials demonstrate rapid and reversible redox behavior, we test the utility of these materials as electrochromes and as active layers in type I aqueous supercapacitors. In both aqueous and organic electrolytes, these materials demonstrate high electrochromic contrasts, with comonomer selection altering the colors of the resultant polymers. As active layers in supercapacitors, all polymers show relatively constant current response as a function of cell voltage, and P­(OE3)-E, in a test device, demonstrates high current retention after 15,000 charge/discharge cycles. This work demonstrates the broad utility of oligoether-functionalized dioxythiophenes for aqueous redox applications while detailing the tuning of optical, electrochemical, and conductance properties through comonomer selection.