Molecular Engineering of Nonhalogenated Solution-Processable Bithiazole-Based Electron-Transport Polymeric Semiconductors

The electron deficiency and trans-planar conformation of bithiazole is potentially beneficial for the electron-transport performance of organic semiconductors. However, the incorporation of bithiazole into polymers through a facile synthetic strategy remains a challenge. Herein, 2,2′-bithiazole was synthesized in one step and copolymerized with di­thienyl­diketo­pyrrolopyrrole to afford poly­(di­thienyl­diketo­pyrrolopyrrole-bithiazole), <b>PDBTz</b>. <b>PDBTz</b> exhibited electron mobility reaching 0.3 cm² V^–1 s^–1 in organic field-effect transistor (OFET) configuration; this contrasts with a recently discussed isoelectronic conjugated polymer comprising an electron-rich bithiophene and dithienyldiketopyrrolopyrrole, which displays merely hole-transport characteristics. This inversion of charge-carrier transport characteristics confirms the significant potential for bithiazole in the development of electron-transport semiconducting materials. Branched 5-decylheptacyl side chains were incorporated into <b>PDBTz</b> to enhance polymer solubility, particularly in nonhalogenated, more environmentally compatible solvents. <b>PDBTz</b> cast from a range of nonhalogenated solvents exhibited film morphologies and field-effect electron mobility similar to those cast from halogenated solvents