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Organic electrochemical transistors (OECTs) are oft-used for bioelectronic applications, and a variety of OECT channel materials have been developed in recent years. However, the majority of these materials are still limited by long-term performance and stability challenges. To resolve these issues, we implemented a next-generation design of polymers for OECTs. Specifically, diketopyrrolopyrrole (DPP) building blocks were copolymerized with propylene dioxythiophene-based (Pro-based) monomers to create a donor-acceptor-type conjugated polymer (PProDOT-DPP). These PProDOT-DPP macromolecules were synthesized using a straightforward direct arylation polymerization synthetic route. The PProDOT-DPP polymer thin film exhibited excellent electrochemical response, low oxidation potential, and high crystallinity, as evidenced by spectroelectrochemical measurements and grazing incidence wide-angle X-ray scattering measurements. Thus, the resultant polymer thin films had high charge mobility and volumetric capacitance values (i.e., μ C * as high as 310 F cm -1 V -1 s -1 ) when they were used as the active layer materials in OECT devices, which places PProDOT-DPP among the highest performing accumulation-mode OECT polymers reported to date. The performance of the PProDOT-DPP thin films was also retained for 100 cycles and over 2000 s of ON-OFF cycling, indicating the robust stability of the materials. Therefore, this effort provides a clear roadmap for the design of electrochemically active macromolecules for accumulation-mode OECTs, where crystalline acceptor cores are incorporated into an all-donor polymer. We anticipate that this will ultimately inspire future polymer designs to enable OECTs with both high electrical performance and operational stability.

Topochemical polymerizations hold the promise of producing high molecular weight and stereoregular single crystalline polymers by first aligning monomers before polymerization. However, monomer modifications often alter the crystal packing and result in non‐reactive polymorphs. Here, we report a systematic study on the side chain functionalization of the bis(indandione) derivative system that can be polymerized under visible light. Precisely engineered side chains help organize the monomer crystals in a one‐dimensional fashion to maintain the topochemical reactivity. By optimizing the side chain length and end group of monomers, the elastic modulus of the resulting polymer single crystals can also be greatly enhanced. Lastly, using ultrasonication, insoluble polymer single crystals can be processed into free‐standing and robust polymer thin films. This work provides new insights on the molecular design of topochemical reactions and paves the way for future applications of this fascinating family of materials. [ABSTRACT FROM AUTHOR]

Incorporation of acceptor‐acceptor (A‐A) type moieties into donor‐acceptor (D‐A) type conjugated polymers becomes a new strategy to tune their electronic properties. In this work, we first demonstrate an efficient convergent route to prepare isoindigo‐based A‐A type building blocks ‐ bis‐isoindigos ‐ via the palladium‐catalyzed oxidative coupling. Bis‐isoindigo‐based polymers show high planarity and delocalized frontier molecular orbitals with lowered LUMO and intact HOMO energy levels, in comparison with their corresponding mono‐isoindigo counterparts. Moreover, fluorine substitution on donors only lowers HOMO levels of Bis‐IID polymers. This study asserts that the D‐A‐A strategy is effective in selectively tuning FMO energy levels of conjugated polymers, complementary to the D‐D‐A approach for the HOMO energy level tuning. Isoindigo‐based A‐A type building blocks, bis‐isoindigos, were synthesized by the palladium‐catalyzed oxidative coupling. Bis‐isoindigo‐based polymers show high planarity and delocalized frontier molecular orbitals with selective tuning ability of LUMO/HOMO levels, complementary to the D‐D‐A approach for the HOMO energy level tuning. [ABSTRACT FROM AUTHOR]