Benzotriazole-Containing Planar Conjugated Polymers with Noncovalent Conformational Locks for Thermally Stable and Efficient Polymer Field-Effect Transistors

Abstract

We report a series of benzotriazole-based semicrystalline π-conjugated polymers with noncovalent conformational locks for applications in polymer field-effect transistors. The benzotriazole moiety is a versatile electron-deficient building block that offers two chemically functionalizable sites, 2(N) and 5, 6(C) positions, allowing easy modulation of the solution processability and electronic structures of the resulting polymers. Fluorine or alkoxy substituents were introduced to the benzotriazole unit to enhance the molecular ordering through intra- and intermolecular F···S, F···H–C, C–F···πF, or S···O attractive interactions. The fluorinated polymer (PTBTz-F) showed remarkably enhanced hole mobility (μh = 1.9 cm2/(V·s), on/off ratio = 8 × 107) upon thermal annealing at 305 °C, compared to the unsubstituted one (PTBTz) (μh = 7.0 × 10–3 cm2/(V·s), on/off ratio = 3 × 106). Alkoxy unit substitution (PTBTz-OR) also improved the carrier mobility up to 0.019 cm2/(V·s) with an on/off ratio of 4 × 105. Fluorine or alkoxy substitution induced tight interchain ordering with edge-on orientation, as confirmed by X-ray diffraction measurements. In particular, fluorinated PTBTz-F showed high thermal stability (T d 453 °C) and the remarkable device characteristics with deep frontier orbital levels.

Highly selective palladium-catalyzed Stille coupling reaction toward chlorine-containing NIR electroluminescent polymers

“…[14][15][16] For the leaving halogen groups in such a reaction, the reactivity of the coupling partner decreases in the order of I > Br > Cl > F. [17][18][19] Among the halides, fluoride is much more stable and is not involved in the reaction, which is a significant advantage and has already been used for the construction of fluorine-containing APCs. [20][21] However, it is a challenge to prepare chlorine-containing aryl compounds by the Stille coupling reaction because the aromatic chloride tends to participate in the reaction, [22][23] resulting in poor selectivity with aromatic bromide or iodide, low yield for the target compound and cross-linking reactions for polymerization. In this context, the complete restraint for the reactivity of chlorine is the key process for the synthesis of chlorine-bearing molecules by Stille coupling reaction, especially for the polymers.…”

Effects of Fluorination and Side Chain Branching on Molecular Conformation and Photovoltaic Performance of Donor–Acceptor Copolymers

“…A similar planarizing effect has been reported previously, which we attribute to a sulphur-fluorine interaction between the fluorinated unit and the bridging T ring. 10,13,30 We speculate that the measured increase in torsion of the BDT-T bond arises because the overall steric hindrance between the branched alkyl side chain and TIPS units is unchanged so the BDT-T bond dihedral must increase to accommodate the planarization of the BTz-T bond.…”

Solubilized 5,6-bis(octyloxy)benzoxadiazole as a versatile acceptor block for designing novel (-X-DADAD-)n and (-X-DADADAD-)n electron donor copolymers for bulk heterojunction organic solar cells

“…It is seen from the Table 1, that hole mobilities of P2 and P3 are 4-10 times higher than that of P1. It is known that alkoxy side chains may lead to a "conformational lock" of the polymer backbone due to noncovalent S…O interactions [36][37][38]. This might be a reason why polymer P2 with increased number of octyloxy side chains per monomer unit shows the enhanced hole mobility as compared to P1.…”