Novel conjugated copolymers with dithienyl and cyclopentadithienyl substituted dicyanoethene acceptor blocks

Novel bifunctional acceptor monomer, 2-[bis(5-bromothiophen-2-yl)methylidene]malononitrile, is obtained in three steps in a total yield of 79%. The Stille cross-coupling between this monomer and 2,6-ditin derivative of 4,4-didecyl-4H-silolo[3,2-b: 4,5-b′]dithiophene afforded donor–acceptor polymer whose properties were compared to the analogue containing a planar cyclopenta[2,1-b: 3,4-b′]dithiophene acceptor block. The copolymers have low narrow optical band gaps and effectively absorb visible light, however the former possesses improved solubility and thermal stability as compared to the latter.