Regioisomerism of an alkyl-substituted bithiophene comonomer in (3E,8E)-3,8-bis(2-oxoindolin-3-ylidene)naphtho-[1,2-b:5,6-b′]difuran-2,7(3H,8H)-dione (INDF)-based D–A polymers for organic thin film transistors†
Two donor–acceptor (D–A) polymers based on (3E,8E)-3,8-bis(2-oxoindolin-3-ylidene)naphtha-[1,2-b:5,6-b′]difuran 2,7(3H,8H)-dione (INDF) and substituted regioisomeric bithiophene (BT) units with different side chain positions (head-to-head, HH, and tail-to-tail, TT) were synthesized. PINDFBT-(HH) achieved electron (μe) and hole (μh) mobilities as high as 0.33 cm2 V−1 s−1 and 0.15 cm2 V−1 s−1, respectively, while PINDFBT-(TT) showed an order of magnitude lower mobilities with μe of 0.07 cm2 V−1 s−1 and μh of 0.02 cm2 V−1 s−1. The distinctly different electrical performance of these two polymers originates from their different side chain placements on the bithiophene units and consequently different electronic structures, backbone coplanarity, chain packing, and thin film morphology. Our results showed that a bithiophene unit with an HH substitution pattern is much more favoured in terms of the charge transport property of the polymers.
- This article is part of the themed collection: 2017 Journal of Materials Chemistry C HOT Papers