Tuning oligo(ether) functionalized dioxythiophene co-polymers for aqueous redox active applications

Aqueous compatible redox active polymers are important for applications ranging from organic electrochemical transistors, conductivity switches, to non-invasive cellular imaging. Oligoether-functionalized dioxythiophenes have been found to be an especially promising class of materials, demonstrating properties such as excellent redox activity, high pseudocapacitance, and electrochromism, making them desirable materials for various applications requiring an active aqueous interface. Recently, the dioxythiophene copolymer ProDOT(OE3)-DMP has been investigated as a polymer for bioelectronics applications. The oligoether side chain (OE3) on the ProDOT unit (3,4-propylenedioxythiophene) serves as the solubilizing unit and the functional moiety which endows the copolymer with aqueous compatibility; incorporation of the spacer unit, 2,2-dimethyl 3,4-propylenedioxythiophene (DMP), improves the electronic properties. As ProDOT(OE3)-DMP has been shown to be broadly useful, we expand on this system with a related family of copolymers. ProDOT(OE3) is copolymerized with different spacer units – 3,4-ethylenedioxythiophene (EDOT) and 3,4-phenylenedioxythiophene (PheDOT) – which incorporate variations in electron richness and planarity due to a mixture of electronic and steric effects. By copolymerizing different monomers with ProDOT(OE3), we tune the switching properties in aqueous electrolytes – modulating the onset of oxidation, the onset of conductance, the switching speeds, and the capacitances. This work constitutes a class of materials that are readily switchable in both organic and aqueous electrolytes and demonstrate rapid optical switching speeds, broad and stable conductance windows, and high capacitances – making them useful as robust, dynamic switching materials for a variety of applications such as brain and body implants, sensors, signal recorders, and neuromorphic systems.