Azaquinoid‐Based High Spin Open‐Shell Conjugated Polymer for n‐Type Organic Field‐Effect Transistors

Abstract An open‐shell quinoidal conjugated polymer exhibiting n‐type semiconducting behavior is successfully synthesized and characterized. An electron‐deficient azaaromatic unit is proven to reduce the energy levels of frontier orbitals via the electronegative nitrogen atom and steric hindrance within the polymer backbone. A synthesized azaquinoidal bithiophene (azaQuBT) is a quinoidal bithiophene that is end‐functionalized with a pyridine ring. The open‐shell quinodial conjugated polymer, poly(azaquinoidal bithiophene‐thiophene), PazaQuBT‐T, is synthesized using azaQuBT and thiophene. The extended quinoidal building block, which has an open‐shell diradical character, induces low bandgaps, redox amphoterism, and high‐spin‐induced paramagnetic behavior of the resulting polymer. PazaQuBT‐T achieves ambipolar charge‐transport behavior in organic field‐effect transistor (OFET) devices. Through a PEIE treatment onto the contact electrode, PazaQuBT‐based OFETs exhibit unipolar n‐channel operation with electron mobility up to 0.98 cm2 V−1 s−1. This work demonstrates the development of novel open‐shell conjugated polymers with high‐spin characteristics and n‐type semiconducting property

Isomer-Free Quinoidal Building Block Employing 3,4-Phenylenedioxythiophene Unit with Mesomeric Effect for Low-Bandgap Quinoidal Conjugated Polymers

Quinoidal compounds have attractive features as organic semiconducting materials owing to their distinct properties compared to aromatic compounds. The suppression of geometrical isomers is a challenge in the development of quinoid-type molecules. In this study, a novel quinoidal building block, bQuPheDOT-Br, was synthesized by incorporating 3,4-phenylenedioxythiophene (PheDOT). Using the conformation-locking strategy, bQuPheDOT-Br exists as a single isomeric compound with a planar molecular structure, resulting in effective π-electron delocalization. Two quinoidal conjugated polymers, PbQPheDOT-T2 and PbQPheDOT-2FT2, were synthesized. Owing to the planar geometry and possible electron delocalization due to the phenyl ring incorporation of the bQPheDOT unit, PbQPheDOT-T2 and PbQPheDOT-2FT2 exhibited a low bandgap (∼1.3 eV) and near-infrared (NIR) light absorption up to 1200 nm wavelength due to the mesomeric effect. Grazing-incidence wide-angle X-ray scattering revealed that both polymers exhibited high crystallinity up to the fourth order of the (h00) diffraction peaks after thermal annealing, owing to their rigid and planar quinoidal backbone. Finally, the charge transport properties of PbQPheDOT-T2 and PbQPheDOT-2FT2 were evaluated by fabricating organic field-effect transistors as active layers with hole mobilities of 5.2 × 10–2 and 2.6 × 10–2 cm2/Vs, respectively, and electron mobility of 1.0 × 10–2 cm2/Vs for PbQPheDOT-T2

Azaquinoid-Based High Spin Open-Shell Conjugated Polymer for n-Type Organic Field-Effect Transistors

An open-shell quinoidal conjugated polymer exhibiting n-type semiconducting behavior is successfully synthesized and characterized. An electron-deficient azaaromatic unit is proven to reduce the energy levels of frontier orbitals via the electronegative nitrogen atom and steric hindrance within the polymer backbone. A synthesized azaquinoidal bithiophene (azaQuBT) is a quinoidal bithiophene that is end-functionalized with a pyridine ring. The open-shell quinodial conjugated polymer, poly(azaquinoidal bithiophene-thiophene), PazaQuBT-T, is synthesized using azaQuBT and thiophene. The extended quinoidal building block, which has an open-shell diradical character, induces low bandgaps, redox amphoterism, and high-spin-induced paramagnetic behavior of the resulting polymer. PazaQuBT-T achieves ambipolar charge-transport behavior in organic field-effect transistor (OFET) devices. Through a PEIE treatment onto the contact electrode, PazaQuBT-based OFETs exhibit unipolar n-channel operation with electron mobility up to 0.98 cm(2) V-1 s(-1). This work demonstrates the development of novel open-shell conjugated polymers with high-spin characteristics and n-type semiconducting property

Enhanced N‑type Semiconducting Performance of Asymmetric Monochlorinated Isoindigo-based Semiregioregular Polymers under Dynamic Forces

The asymmetric monochlorination strategy not only effectively addresses the steric issues in conventional dichlorination but also enables the development of promising acceptor units and semiregioregular polymers. Herein, monochlorinated isoindigo (1CIID) is successfully designed and synthesized by selectively introducing single chlorine (Cl) atoms. Furthermore, the 1CIID copolymerizes with two donor counterparts, centrosymmetric 2,2′-bithiophene (2T) and axisymmetric 4,7-di(thiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT), forming two polymers, P1CIID-2T and P1CIID-DTBT. These polymers exhibit notable differences in backbone linearity and dipole moments, influenced by the symmetry of their donor counterparts. In particular, P1CIID-2T, which contains a centrosymmetric 2T unit, demonstrates a linear backbone and a significant dipole moment of 10.20 D. These properties contribute to the favorable film morphology of P1CIID-2T, characterized by highly ordered crystallinity in the presence of fifth-order (500) X-ray diffraction peaks. Notably, P1CIID-2T exhibits a significant improvement in molecular alignment under dynamic force, resulting in over 8-fold improvement in the performance of organic field-effect transistor (OFET) devices, with superior electron mobility up to 1.22 cm2 V−1 s−1. This study represents the first synthesis of asymmetric monochlorinated isoindigo-based conjugated polymers, highlighting the potential of asymmetric monochlorination for developing n-type semiconducting polymers. Moreover, our findings provide valuable insights into the relationship between the molecular structure and properties

Effects of advanced treatments using granular activated carbon adsorption with ozonation and ultrafiltration on chlorine decay

The application of advanced treatment processes has been substantially increased to comply with regulations on microbial inactivation and disinfection by-products. The advanced processes, such as ozonation followed by granular activated carbon or ultrafiltration, yield changes in chemical properties of the treated water in addition to the improvement of water quality. The changes in water chemistry could affect the kinetics of disinfectant decay within the water distribution system. In addition, decay behaviors using various pipe materials were investigated with water that underwent advanced treatments. The permeate from ultrafiltration generally shows lower decay rate constants than that of effluents from ozonation + granular activated carbon adsorption. The differences were especially obvious for so-called unreactive pipe coupons such as polyvinyl chloride (PVC), polyethylene (PE), polycarbonate (PC), and stainless steel. Reactive pipe materials, such as cast iron and copper, had almost 10 times higher rate constants than the unreactive pipes, regardless of the applied treatment processes. Appropriate safety actions should be introduced to ensure high quality of drinking water in a distribution system prior to changing processes in water treatment plants.close0