Conjugated copolymers based on fluorene -thieno [3,2 -b]thiophene for light-emitting diodes and photovoltaic cells

Alternating conjugated copolymers comprised of 9,9-dihexylfluorene and unsubstituted/substituted thieno[3,2-b]thiophene moieties were synthesized using the Suzuki coupling reaction. The structures of these polymers were characterized, and their thermal, photophysical, electrochemical, and electroluminescent properties were investigated. By β-substitution of thieno[3,2-b]thiophene moiety with alkyl chain, the thermal, electrochemical, and electroluminescence properties of the resulted polymers were tuned. The polymers exhibited good thermal stability with decomposition temperature (Td) in the region of 308−431 °C and their glass transition temperatures (Tg) ranging from 126 to 146 °C. Incorporation of β-alkyl chain onto thieno[3,2-b]thiophene of the alternating copolymers led to lowered Tdand Tg and blue-shifted maximum wavelengths in both absorption and emission spectra. The influence of β-alkyl substitution on the conformation of the polymer chains was evaluated by simulating the optimized geometries of ...