Synthesis and characterization of fluorine–thiophene-based π-conjugated polymers using coupling reaction

A solution processible fluorine–thiophene-based copolymers, namely poly[2,7-bis(4-octyl-2-thienyl)-9,9-dioctylfluorene-co-alt-5,5′-(2,2′-bithiophene)] (P1), poly[2,7-bis(3-octyl-2-thienyl)-9,9-dioctylfluorene-co-alt-5,5′-(2,2′-bithiophene)] (P2), poly[2,7-bis(3,3′-dioctyl-5,5′-bithien-2yl)-9,9′-dioctylfluorene-co-alt-5,5′-(2,2′-bithiophene)] (P3) were synthesized using Suzuki and Stille coupling reaction. The polymers showed weight loss starting around 400 °C indicative of good thermal stability. UV–vis properties and photoluminescence (PL) properties were investigated in toluene. P1, P2 and P3 exhibited the absorption maximum at 450, 428 and 435 nm and their PL spectrum peaked at 587, 559 and 560 nm, respectively. And all polymers, P1, P2 and P3, showed electroluminescence (EL) spectrum peaked at 592, 595 and 607 nm in the range of orange red. The polymers were electrochemically active in oxidation regions. P3 especially showed high oxidation stabilities in 1.17 V vs. Ag/Ag+. And P1 and P3 showed higher crystallinity than P2, because they have a repeated unit of 3,3‴-dialkyl-quaterthiophene.