Poly(thieno[3,4-]pyrazine--2,1,3-benzothiadiazole)s: A New Design Paradigm in Low Band Gap Polymers.

A new design paradigm for the production of low band gap polymers is reported, in which an ambipolar unit exhibiting both donor and acceptor properties is combined with a conventional acceptor. As initial examples of this approach, the synthesis of two alternating copolymers of thieno[3,4-]pyrazine and 2,1,3-benzothiadiazole via direct arylation polymerization is reported to give soluble, processable materials with band gaps of 0.97 and 1.05 eV. Although direct arylation polymerization has been previously used to synthesize donor-acceptor materials with band gaps below 1.5 eV, this represents only the second material generated by this polymerization method with a band gap below 1.0 eV.