An N-oxide containing conjugated semiconducting polymer with enhanced electron mobility via direct (hetero)arylation polymerization

Abstract

In this paper, an N-oxide building block, 4,4′-dimethyl-[2,2′-bithiazole] 3,3′-dioxide (MeBTzO), was designed and synthesized by oxidation of sp²-N in the aromatic ring. Theoretical calculation results showed that MeBTzO has higher reactivity than its non-oxide sp²-N containing monomer MeBTz in direct (hetero)arylation polymerization (DHAP). Therefore, an N-oxide containing conjugated semiconducting polymer, PDPPMeBTzO, was successfully synthesized via DHAP of MeBTzO with thiophene-flanked diketopyrrolopyrrole (DPP). PDPPMeBTzO possesses a lower lowest unoccupied molecular orbital (LUMO) than the non-oxide analogous polymer PDPPMeBTz, which will facilitate electron injection and transport in organic field-effect transistors (OFETs). As a result, PDPPMeBTzO has obviously enhanced electron transport properties with a higher μ_e of 0.11 cm² V⁻¹ s⁻¹ compared to PDPPMeBT with a μ_e of 7.49 × 10⁻³ cm² V⁻¹ s⁻¹. Our strategy demonstrated that introducing the N-oxide group in conjugated polymers has great potential for high performance ambipolar and n-type CSP materials.