Chain microstructure and specific features of excitation energy transfer in solution and films of poly(9,9-dioctylfluorene) doped with 2,1,3-benzothiadiazole comonomer units

•Copolyfluorenes of the same composition were obtained by Suzuki and Yamamoto methods.•The conjugation length of copolymers was estimated from Kerr effect data in solution.•The luminescent properties of both copolymers were quite different.•Differences in luminescent properties are due to variations of chain microstructure.•The Yamamoto type copolymer displays an efficient white electroluminescence.