This work presents a soluble oligo(ether)-functionalized propylenedioxythiophene (ProDOT)-based copolymer as a versatile platform for a range of high-performance electrochemical devices, including organic electrochemical transistors (OECTs), electrochromic displays, and energy-storage devices. This polymer exhibits dual electroactivity in both aqueous and organic electrolyte systems, redox stability for thousands of redox cycles, and charge-storage capacity exceeding 80 F g −1 . As an electrochrome, this material undergoes full colored-to-colorless optical transitions on rapid time scales (<2 s) and impressive electrochromic contrast (Δ%T > 70%). Incorporation of the polymer into OECTs yields accumulation-mode devices with an I ON/OFF current ratio of 10 5 , high transconductance without post-treatments, as well as competitive hole mobility and volumetric capacitance, making it an attractive candidate for biosensing applications. In addition to being the first ProDOT-based OECT active material reported to date, this is also the first reported OECT material synthesized via direct(hetero)arylation polymerization, which is a highly favorable polymerization method when compared to commonly used Stille cross-coupling. This work provides a demonstration of how a single ProDOTbased polymer, prepared using benign polymerization chemistry and functionalized with highly polar side chains, can be used to access a range of highly desirable properties and performance metrics relevant to electro chemical, optical, and bioelectronic applications. Electroactive Polymers[+] Present address:

Replacing the alkyl side chains on conventional semiconducting polymers with ethylene glycol (EG) based chains is a successful strategy in the molecular design of mixed conduction materials for bioelectronic devices, including organic electrochemical transistors (OECTs). Such polymers have demonstrated the capability to conduct both ionic and electronic charges and can offer superior performance compared to the most commonly used active material, poly(3,4ethylenedioxythiophene):poly(styrenesulfonate). While many research efforts have been dedicated to optimizing OECT performance through the engineering of the semiconducting polymers' conjugated backbones, variation of the EG chain length has been investigated considerably less. In this work, a series of glycolated polythiophenes with pendant EG chains spanning two to six EG repeat units was synthesized and the electrochemical and structural characteristics of the resulting films were characterized by experimental means and molecular dynamics simulations. OECTs were fabricated and tested, and their performance showed a strong correlation to the length of the EG side chain length, thereby elucidating important structure-property guidelines for the molecular design of future channel materials. Specifically, a careful balance in the EG length must be struck during the design of EG functionalized conjugated polymers for OECTs. While minimizing the EG side chain length appears to boost both the capacitive and charge carrier transport properties of the polymers, the chosen EG side chain length must be kept sufficiently long to induce solubility for processing, and allow for the necessary ion interactions with the conjugated polymer backbone.

The processability and electronic properties of conjugated polymers (CPs) have become increasingly important due to the potential of these materials in redox and solid-state devices for a broad range of applications. To solubilize CPs, side chains are needed, but such side chains reduce the relative fraction of electroactive material in the film, potentially obstructing π−π intermolecular interactions, localizing charge carriers, and compromising desirable optoelectronic properties. To reduce the deleterious effects of side chains, we demonstrate that postprocessing side chain removal, exemplified here via ester hydrolysis, significantly increases the electrical conductivity of chemically doped CP films. Beginning with a model system consisting of an ester functionalized ProDOT copolymerized with a dimethylProDOT, we used a variety of methods to assess the changes in polymer film volume and morphology upon hydrolysis and resulting active material densification. Via a combination of electrochemistry, X-ray photoelectron spectroscopy, and charge transport models, we demonstrate that this increase in electrical conductivity is not due to an increase in degree of doping but an increase in charge carrier density and reduction in carrier localization that occurs due to side chain removal. With this improved understanding of side chain hydrolysis, we then apply this method to high-performance ProDOT-alt-EDOT x copolymers. After hydrolysis, these ProDOT-alt-EDOT x copolymers yield exceptional electrical conductivities (∼700 S/cm), outperforming all previously reported oligoether-/glycol-based CP systems. Ultimately, this methodology advances the ability to solution process highly electrically conductive CP films.

are useful for communicating text and complex images via reflective displays in electronic paper devices, wearable "smart glasses," and transmissive panel monitors. Essential to the utility of such materials is the ability to repeatedly transition between two optical states in a rapid, on-demand fashion.π-Conjugated electrochromic polymers (ECPs) are a class of electrochromic materials that offer an appealing platform for the realization of true black-to-transmissive electrochromism. ECPs can undergo full colored-to-colorless transitions on rapid time scales (often in second to subsecond regimes, [1] with high coloration efficiencies, contrasts (Δ%T at λ max ) up to 70%, switching stability over thousands to hundreds of thousands of cycles, and in many cases, colorless states that can be refreshed by a small current or voltage pulse. [1,2] Moreover, ECPs can be readily tuned for color through straightforward chemical modification of the polymer backbone. The addition of solubilizing aliphatic or polar side chains allows for these materials to be processed as electronic inks in low-cost and large-scale processing techniques, such as inkjetprinting, along with blade-, spray-, and slot die coating. [3][4][5][6][7][8][9][10] In recent years, a deeper understanding of the structure-property relationships that control the color and switching properties of ECPs has enabled the development of extensive libraries of cathodically coloring polymers. These materials have been successfully integrated into plastic [5,11,12] and paper-based [7,13,14] electrochromic devices, making them promising candidates for flexible or transient electronic displays.While most colored-to-transmissive ECPs have π-electronic structures that have been carefully modified to absorb specific wavelengths of visible light for achieving highly saturated colors, a black ECP must absorb across the entire visible spectrum in its colored state. Meanwhile, the transmissive state of the material must absorb as little visible light as possible in the same wavelength range for optimal contrast and optical clarity. Developing a material that undergoes such drastic spectral changes upon application of an electrical bias presents a unique materials design challenge. An additional complexity arises when seeking to develop black-to-transmissive electrochromic materials that are able to transition through intermediate shades of gray, as well. Next-generation electrochromic technologies, such as dimmable fenestration, eyewear integrated displays, and optical shutters require materials that reversibly transition between highly transmissive and broadly absorbing achromatic states, often with minimal intermediate coloration. In this work, it is shown how the properties of dioxythiophene-based electrochromic polymers (ECPs) can be leveraged through straightforward color mixing to yield high-contrast, black-to-transmissive materials with low driving voltages (<1 V), extended functional lifetimes, and minimal transient chromaticity.Drawing from a family of five soluble co...

Discovery of structure−property interrelations in organic electrochemical transistors (OECTs) is limited by the small number of high-performing semiconducting polymer families that are electrochemically active in aqueous media. Currently, state-of-the-art polymers often come with processability drawbacks; aqueous-processable polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PE-DOT:PSS) require insulating cross-linkers to protect against dissolution in aqueous electrolyte, while glycolated polymers frequently exhibit marginal solubility in both organic and aqueous solvents. Herein, we show that the carboxylic acidfunctionalized conjugated polymer poly [3-(4-carboxypropyl)thiophene] (P3CPT) can be processed from a water-soluble precursor, yet requires no additives to yield solvent-resistant OECTs which exhibit electroactivity in aqueous and organic electrolytes. Devices fabricated with P3CPT exhibit unipolar p-channel operation in accumulation mode, with maximum transconductance of 26 ± 2 mS on interdigitated electrodes and competitive volumetric capacitance (C*) of 150 ± 18 F-cm −3 , which rank amongst the highest for conjugated polymers with ionic side chain moieties. This work paves the way for future use of carboxylic acid functionalization to modify existing p-and n-channel backbones to yield highly competitive and processable OECT active materials.

We address the nature of electrochemically induced charged states in conjugated polymers, their evolution as a function of electrochemical potential, and their coupling to their local environment by means of transient absorption and Raman spectroscopies synergistically performed in situ throughout the electrochemical doping process. In particular, we investigate the fundamental mechanism of electrochemical doping in an oligoether-functionalized 3,4propylenedioxythiophene (ProDOT) copolymer. The changes embedded in both linear and transient absorption features allow us to identify a precursor electronic state with charge-transfer (CT) character that precedes polaron formation and bulk electronic conductivity. This state is shown to contribute to the ultrafast quenching of both neutral molecular excitations and polarons. Raman spectra relate the electronic transition of this precursor state predominantly to the C β -C β stretching mode of the thiophene heterocycle. We characterize the coupling of the CT-like state with primary excitons and electrochemically induced charge-separated states, providing insight into the energetic landscape of a heterogeneous polymer-electrolyte system and demonstrating how such coupling depends on environmental parameters, such as polymer structure, electrolyte composition, and environmental polarity.

Understanding the impact of side chains on the aqueous redox properties of conjugated polymers is crucial to unlocking their potential in bioelectrochemical devices, such as organic electrochemical transistors (OECTs).Here, we report a series of polar propylenedioxythiophene-based copolymers functionalized with glyme side chains of varying lengths as well as an analogue with short hydroxyl side chains. We show that long polar side chains are not required for achieving high volumetric capacitance (C*), as short hydroxy substituents can afford facile doping and high C* in saline-based electrolytes. Furthermore, we demonstrate that varying the length of the polar glyme chains leads to subtle changes in material properties. Increasing the length of glyme side chain is generally associated with an enhancement in OECT performance, doping kinetics, and stability, with the polymer bearing the longest side chains exhibiting the highest performance ([μC*] OECT = 200 ± 8 F cm −1 V −1 s −1 ). The origin of this performance enhancement is investigated in different device configurations using in situ techniques (e.g., time-resolved spectroelectrochemistry and chronoamperometry). These studies suggest that the performance improvement is not due to significant changes in C* but rather due to variations in the inferred mobility. Through a thorough comparison of two different architectures, we demonstrate that device geometry can obfuscate the benchmarking of OECT active channel materials, likely due to contact resistance effects. By complementing all electrochemical and spectroscopic experiments with in situ measurements performed within a planar OECT device configuration, this work seeks to unambiguously assign material design principles to fine-tune the properties of poly(dioxythiophene)s relevant for application in OECTs.

conjugated polymers (CPs) with tunable electronic properties will remain a challenge without adequate solution processability due to the importance of techniques such as roll-to-roll manufacturing. Consequently, modifying CP backbones with polar side chains has recently resurged as an attractive structural design approach to improve polymer solubility and to provide CPs with the capability of transporting both electrons and ions, which is crucial for applications such as organic electrochemical transistors (OECTs). Here, a new dioxythiophene copolymer comprised of 2, 2'-bis-(3,4-ethylenedioxy)thiophene (biEDOT) and 3,4-propylenedioxythiophene (ProDOT) substituted with branched oligo(ether) side chains (PE 2 -biOE2OE3) is synthesized using two direct hereto(arylation) polymerization (DHAP) techniques. The typical DHAP technique results in a lower molecular weight polymer (PE 2 -biOE2OE3(L)), which is soluble in acetone and demonstrated a solid-state conductivity after oxidative doping of 55 ± 3 S cm −1 . Alternatively, a unique temperature ramp DHAP methodology results in a higher molecular weight polymer (PE 2 -biOE2OE3(H)) with an especially high solidstate conductivity of 430 ± 60 S cm −1 . Notably, the first OECT fabricated from an acetone-processed polymer is reported, which is stable up to 500 cycles and can provide a pathway for future material design aimed at eliminating the use of toxic chlorinated solvents in OECT active layer processing.