Conjugated Polyelectrolytes as Water Processable Precursors to Aqueous Compatible Redox Active Polymers for Diverse Applications: Electrochromism, Charge Storage, and Biocompatible Organic Electronics

Abstract

An organic soluble precursor polymer was prepared by direct (hetero)­arylation polymerization of 3,4-ethylenedioxythiophene (EDOT) with a solubilizing, 3,4-propylenedioxythiophene (ProDOT) derivative bearing ester-functionalized side chains. Chemical defunctionalization of the polymer, using base to hydrolyze the esters, yields a conjugated polyelectrolyte (CPE) that is readily soluble in water. This aqueous soluble CPE can then be processed using high-throughput coating methods from water-based inks. Postprocessing functionalization of the polymer film using dilute acid creates a solvent resistant film that is compatible with both organic and aqueous electrolyte systems for redox switching. The introduction of an unfunctionalized EDOT unit results in a soluble polymer that has a low oxidation potential and that is highly electroactive and pseudocapacitive in a wide voltage range (2 V in propylene carbonate-based electrolytes and 1.55 V in aqueous electrolytes) making it an attractive material for lightweight and flexible supercapacitors. Films of this copolymer demonstrate exceptionally rapid redox switching (10 V/s) and higher mass capacitance in aqueous electrolyte solutions than in organic solutions. Supercapacitors incorporating the solvent resistant copolymer exhibit symmetric charge/discharge behavior at currents of up to 20 A/g (1 s discharge) and are able to maintain >75% of the initial capacitance over 175 000 cycles using 0.5 M NaCl/water as the device electrolyte. Rapid electrochromic switching (∼0.2 s) from vibrant blue to colorless is also maintained in this salt–water electrolyte. The versatility of this polymer is further shown in a series of organic and aqueous electrolyte systems, including biologically compatible electrolytes (NaCl/water, Ringer’s solution, and human serum) and even sport drinks (Gatorade and Powerade), demonstrating the robustness of this polymer to differing ionic conditions. Based on these results, it is apparent that this polymer and similar systems have great potential in multiple electrochemical applications such as electrochromic devices, supercapacitors, and biocompatible devices.

Balancing Charge Storage and Mobility in an Oligo(Ether) Functionalized Dioxythiophene Copolymer for Organic‐ and Aqueous‐ Based Electrochemical Devices and Transistors

“…Developing alternative aqueous‐compatible CPs frequently involves: (i) the incorporation of electron‐rich heterocycles into the polymer backbone that can stabilize positive charge carriers through delocalization, affording materials with redox potentials within the electrochemical window of water, and (ii) functionalization of the polymer backbone with polar groups to assist in the penetration and transport of hydrated electrolyte ions. The latter can be accomplished by targeted postpolymerization modifications that convert hydrophobic, aliphatic side chains required for synthesis and purification with polar groups, such as alcohols and carboxylic acids . Alternatively, the monomer precursor can be functionalized with highly polar side chains, such as oligo(ether), ester, or amide groups, prior to polymerization.…”

Conductive, Solution‐Processed Dioxythiophene Copolymers for Thermoelectric and Transparent Electrode Applications

“…[18,19] Additionally, the broad electroactive response of the high EDOT content polymers in the ProDOT x -EDOT y (P x E y ) series has led to them being effective as capacitive materials for charge storage applications. [20][21][22] In our previous work, we have shown that increasing the EDOT content in the repeat unit of these copolymers lowers the onset of oxidation, increases the capacitance, and lowers the optical gap (E g ) of the resulting material. This trend and the relevant polymer structures are shown in Scheme 1.…”

The Effect of Oligo(Ethylene Oxide) Side Chains: A Strategy to Improve Contrast and Switching Speed in Electrochromic Polymers

“…[36] Besides, other highly polar chains e. g. ester and carboxylate salt have also been introduced into ProDOT. [37][38][39] However, few attempts are reported to develop the TT-based structure, though they have been widely employed in organic photovoltaics (OPV), [40] and organic thinfilm transistors (OTFTs). [41] Encouraged by these studies, we herein propose a facile molecular-design strategy to enhance the contrast and switching speed in ECP films ( Figure 1).…”