Developments in the chemistry and band gap engineering of donor-acceptor substituted conjugated polymers

This paper reviews the tools to manipulate and minimize the band gap of con jugated (co)polymers. The effects of minimization of the bond length altern ation and of the incorporation of donor-K-acceptor units are discussed in p articular. A systematic study of a series of alternating donor-acceptor oli gomers has revealed the achievable limits and allowed for a prognosis of th e performance of corresponding copolymers. The decisive influence of the LU MO eigenvectors of the accepters on the band gap is highlighted. A new synt hesis of benzo[1,2-c:4,5-c]bis[1,2,5]thiadiazole containing donor-acceptor monomers and their acid-catalyzed polymerization are described. Finally, ba nd gap tuning by appropriate substitution, conformational adjustment and me soscopic ordering is discussed. (C) 2001 Elsevier Science B.V. All rights r eserved.