The effect of the presence of hexyl group in thiophene on the photophysical and electrochemical properties of poly[(9,9-dioctyluorene)-2,7-diyl-alt-(4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole)-2,2-diyl] (F8TBT) is investigated. The copolymers present electron donor-acceptor architecture and are synthesized by Suzuki coupling reaction. The UV/Vis spectra show absorption maximum in the wavelength range of blue and orange, which are associated with different segments of the polymer backbone. Addition of hexyl substituent groups has a positive effect on the molar absorptivity and increases the emission and absorption intensities due to fluorene and thiophene-benzothiadiazole-thiophene (TBT) units, although an increment in the bandgap is observed. Cyclic voltammetry study of the polymer films reveal irreversible reduction and oxidation processes of the TBT units in the polymer chain and the HOMO and LUMO energy levels suggest ambipolar character for the polymers, while the electrochemical bandgaps are consistent with the absorbance measurements. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1975-1982