Direct arylation polymerization toward ultra-low bandgap poly(thienoisoindigo-alt-diketopyrrolepyrrole) conjugated polymers: The effect of β-protection on the polymerization and properties of the polymers

Direct arylation polymerization between derivatives of dibromodiketopyrrolopyrrole (DPP) and thienoisoindigo (TIIG) resulted in two -conjugated copolymers with average molecular weights up to 24.0 kDa and bandgaps as low as 0.8 eV. The structural analysis of the obtained two polymers revealed well-defined alternating conjugation backbones without obvious structural defects. The introduction of hexyl-group in the -position of thiophene rings in the DPP units not only reduces the bandgap of conjugated polymer compared to a similar polymer containing bare-thiophene flanked DPP but also affects polymer morphology in thin films. P-type charge-transport characteristics were observed for two polymers in organic field-effect transistors with comparable hole mobilities. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3205-3213