Mesopolymer synthesis by ligand-modulated direct arylation polycondensation towards n-type and ambipolar conjugated systems.

Conjugated polymers are attractive components for plastic electronics, but their structural defects, low solubility and batch-to-batch variation-mainly in terms of molecular weight and dispersity-hinder practical applications. Here, we demonstrate that these issues can be circumvented by using conjugated mesopolymers, which have the advantages of both oligomers and polymers. A diketopyrrolopyrrole monomer and a benzothiadiazole derivative react through direct arylation polycondensation, promoted by sterically hindered adamantyl ligand coordinated palladium catalysts, to form mesopolymers. The reaction is facile, environmentally benign (it does not require tin or boron reagents) and occurs in high yields. The resulting mesopolymers have a strictly alternating donor-acceptor structure, without detectable homocoupling and β-arylation defects, and exhibit number-averaged molecular weights (Mn) between 1 and 10 kDa. They also show good solution processability and have significantly enhanced electron mobilities, which makes them n-type and ambipolar semiconductors, with advantages over their polymer counterparts.