Branched alkyl ester side chains rendering large polycyclic (3E, 7E)-3, 7-bis(2-oxoindolin-3-ylidene)benzo[1, 2-b:4, 5-b′]difuran-2, 6(3H, 7H)-dione (IBDF) based donor–acceptor polymers solution-processability for organic thin film transistors1. Issue 37 (7th October 2015)