Color tuning in polyfluorenes by copolymerization with low band gap comonomers

Poly(9,9-dialkylfluorene-2,7-diyl) derivatives containing low band gap comonomers, have been synthesized through Ni(0) mediated Yamamoto polymerization. High molecular weight and thermally stable polymers were obtained which could be processed in common organic solvents. The absorption and fluorescence spectra of the new polymers were recorded. The fluorescence maxima of the copolymers red-shift as the band gap of the comonomer decreases. Although substituted fluorene homopolymers showed excimer emission after annealing at elevated temperature, excimer formation upon annealing was suppressed by incorporating low band gap comonomers into the fluorene main chain. In this paper, color tuning, exciton migration and trapping and the formation of excimers in poly(fluorene) derivatives is discussed.