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Flexible temperature sensors based on π–conjugated polymers are well‐suited for diverse applications, including food packaging and human health monitoring. Herein, novel dihydropyrazine (DHP)‐based polymers designed for the development of flexible temperature sensors are introduced. The DHP‐based polymers are synthesized via direct arylation polymerization, eliminating toxic byproducts. Polymers with carboxylate potassium salt side chains, which exhibit high solubility in green solvents like water and alcohol are obtained via post‐polymerization hydrolysis of carboxylate ester chains. Furthermore, a post‐deposition treatment converts the carboxylate potassium salt side chains into carboxylic acid side chains, resulting in highly solvent‐resistant polymers. Notably, these DHP‐based polymers exhibit moderate electrical conductivity in the range of ≈10−4 to 10−1 S cm−1 without the need for additional dopants. Resistor‐type temperature sensors based on the self‐doped DHP‐based polymers, processed with ethylene glycol (EG) on flexible polyethylene terephthalate (PET) substrates via blade coating, demonstrate an impressive temperature coefficient of resistance (TCR) of up to −1.5% °C−1 (20–60 °C) and outstanding long‐term stability under ambient conditions. This work presents a well‐founded design of π–conjugated polymers that simultaneously fulfill performance, stability, processability, and cost criteria, paving the way for practical applications of flexible and printable temperature sensors. [ABSTRACT FROM AUTHOR]

A novel donor–acceptor (D‐A) conjugated polymer, poly[bis(2‐ethylhexyl)3‐(3′′,4′‐bis(dodecyloxy)‐[2,2′:5′,2′′‐terthiophen]‐5‐yl)‐1,4‐dioxo‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐2,5(1H,4H)‐dicarboxylate] (PDEB), comprising an electron‐accepting carbamate side‐chain bearing thiophene‐flanked diketopyrrolopyrrole (DPPTh) and an electron‐donating 3,3′‐bis(dodecyloxy)‐2,2′‐bithiophene (C12‐BTO) is synthesized. The carbamate side‐chains in this polymer can be thermally removed at a moderate temperature, forming an insoluble polymer poly[3‐(3″,4′‐bis(dodecyloxy)‐[2,2′:5′,2″‐terthiophen]‐5‐yl)‐6‐(thiophen‐2‐yl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione] (PDNB) with high solvent resistance. PDNB has a high highest occupied molecular orbital energy level of −4.68 eV and a narrow band gap of 1.05 eV, which makes it dopable by HCl to form a stable conductive polymer PDNB:HCl with moderate conductivity of 0.24 S cm–1. A chemiresistive sensor based on PDNB:HCl can distinguish ten common volatile organic liquids with unique current–time profiles under a low operation voltage of 1 V. Importantly, a single sensor can be used many times and remain functional over a long period of time in air, indicating its extraordinary operational and environmental stability. The results demonstrate that PDNB is a promising material for reusable chemiresistive sensors. [ABSTRACT FROM AUTHOR]

A series of conjugated polymers and oligomers previously used in organic photovoltaics and organic light-emitting diodes (OLEDs) have been examined for the first time as photoinitiators of polymerization. They address the present and future challenges facing photopolymerization: requirement of high extinction molar coefficients, absorption over the whole visible spectrum, ability to easily withdraw or release electrons. Interestingly, these compounds initiate the cationic polymerization of epoxides or the free radical polymerization of acrylates upon exposure of the photocurable formulations to a LED emitting at 405 nm. Some of them can potentially operate under blue, green, or red laser diodes. [ABSTRACT FROM AUTHOR]

Three thiophene- S, S-dioxidized indophenine (IDTO) isomers, 3 a ( E, E, E), 3 b ( Z, E, E), and 3 c ( Z, E, Z), were synthesized by oxidation of an indophenine compound. 3 b and 3 c could be converted into the most-stable 3 a by heating at 110 °C. An IDTO-containing conjugated polymer, PIDTOTT, was prepared using 3 a as a comonomer through a Stille coupling reaction, and it possesses a narrow band gap and low energy levels. In organic field effect transistors (OFETs), PIDTOTT exhibited unipolar n-type semiconductor characteristics with unexpectedly high electron mobility (up to 0.14 cm2 V−1 s−1), despite its rather disordered chain packing. [ABSTRACT FROM AUTHOR]

We report two new low band-gap conjugated polymers containing dipyrrolo[2,3-b:2′,3′-e]pyrazine-2,6(1H,5H)-dione (PzDP), PPzDPDP-BT and PPzDPDP-TT, both showing ambipolar transport in organic thin film transistors (OTFTs), with hole mobility up to 0.066 cm2 V−1 s−1, electron mobility up to 0.021 cm2 V−1 s−1, and high current on-to-off ratios of 105–106. [ABSTRACT FROM AUTHOR]

Two new π-conjugated polymers with donor backbone and π-conjugated indolin-2-one side chains, PBDTTI and PBDTTIF, are designed and synthesized as wide bandgap donors for non-fullerene acceptor-based organic solar cells (OSCs). The monomers containing electron accepting indolin-2-one side chains, (Z)-3-((2,5-dibromothiophen-3-yl) methylene)-1-methylindolin-2-one (M1) and (Z)-3-((2,5-dibromothiophen-3-yl) methylene)-5-fluoro-1-methylindolin-2-one (M2), can be easily synthesized via Knoevenagel condensation between 2,5-dibromothiophene-3-carbaldehyde and 2-oxindole or 5-fluoro-2-oxindole, respectively. Stille coupling polymerization of the electron donating benzodithiophene (BDT)-containing monomer 1,1′-[4,8-bis [5-(2-ethylhexyl)-2-thienyl]benzo [1,2- b :4,5- b ′]dithiophene-2,6-diyl]bis [1,1,1-trimethylstannane] and M1 or M2 produced PBDTTI or PBDTTIF, respectively. The strong electron accepting π-conjugated 1-methylindolin-2-one and 5-fluoro-1-methylindolin-2-one side chains can achieve low-lying HOMO energy levels of −5.59 eV for PBDTTI and −5.60 eV for PBDTTIF, which is beneficial for realizing high open circuit voltage (V OC) of the resulting OSCs. On the other hand, since the electron acceptor units are on the side chains, the polymer backbone containing only electron donor units could maintain wide bandgaps of 1.91 eV and 1.89 eV for PBDTTI and PBDTTIF, respectively. When PBDTTI and PBDTTIF were used as donors and a small bandgap non-full acceptor ITIC as an acceptor, the resulting OSCs devices achieved V OC of 0.97 and 1.00 V, short circuit current densities (J SC) of 15.60 and 13.70 mAcm-2, and fill factors (FF) of 0.60 and 0.59, resulting in power conversion efficiencies of 8.00 and 7.70%, respectively. [Display omitted] • Two new donor-backbone and acceptor-side chain polymer donors are synthesized. • Low frontier energy levels and wide bandgap are achieved. • Organic solar cells using these polymer donors showed promising performance. [ABSTRACT FROM AUTHOR]