Thienoisoindigo-based Conjugated Polymers Synthesized by Direct Arylation Polycondensation.

A series of thienoisoindigo (TIG)-based conjugated polymers (CPs) with high molecular weights are synthesized by direct arylation polycondensation (DArP) by using TIG derivatives as C-Br monomer and multi-halogenated thiophene derivatives, i.e., 1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT), 1,2-bis(3,4-dichlorothien-2-yl)ethene (4ClTVT), 3",3",4",4"-tetrafluoro-2",2"-bithiophene (4FBT) and 3",3",4",4"-tetrachloro-2",2"-bithiophene (4ClBT), as C-H monomers. Density functional theory (DFT) calculations reveal the high selectivity between α-C-H bonds in 4FTVT, 4ClTVT, 4FBT and 4ClBT and β-C-H bonds in TIG C-Br monomer. All four resulting CPs exhibit low optical bandgaps of ca. 1.20 eV and ambipolar transport characteristics with both electron and hole mobility above 0.1 cm 2 V -1 s -1 as elaborated with organic thin-film transistors (OTFTs). The polymer TIG-4FTVT delivers the best device performance. With this polymer, n-channel OTFTs with electron mobility up to 1.67 cm 2 V -1 s -1 and p-channel OTFTs with hole mobility up to 0.62 cm 2 V -1 s -1 have been fabricated by modifying source/drain electrodes with polyethylenimine ethoxylated (PEIE) and MoO 3 , respectively, to selectively inject electrons and holes. This article is protected by copyright. All rights reserved.