Band gap tuning of new light emitting conjugated polymers

A series of copolymers, poly{9,9-bis(2′-ethylhexyl)fluorene-2,7-diyl-co-2,5-bis(2-thienyl-1-cyanov inyl)-1-(2′-ethylhexyloxy)-4-methoxybenzene-5″,5‴-diyl} has been synthesized from the monomers, 2,7-dibromo-9,9-bis(2′-ethylhexyl)fluorene and 2,5-bis(2-(5′-bromothienyl)-1-cyanovinyl)-1-(2″-ethylhexyloxy)-4-met hoxybenzene (BTCVB) using the Ni(0) mediated polymerization. The synthesized copolymers showed the absorption maxima at about 380 nm and the absorption between 425 and 600 nm increased as the fraction of the thiophene-containing monomer (BTCVB) increased. In photoluminescence (PL), the emission maxima of the copolymers were red-shifted as the fraction of BTCVB increased, despite the similar absorption characteristics were shown in the UV-vis spectra. The copolymer containing 15 mol% of BTCVB showed a maximum PL emission at 620 nm.