2,7‐dibromo‐9,9‐bis(perfluorohexylethyl propionate) fluorene was synthesized by Michael addition reaction using 2,7‐dibromofluorene and perfluorohexyl ethyl acrylate as the reactants. 9,9‐Bis(perfluorohexylethyl propionate) fluorene copolymers were then synthesized by Suzuki coupling reaction with 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborane‐diyl)‐9,9 ‐dioctyl fluorene, 2,7‐dibromo‐9,9‐dioctyl fluorene and 2,7‐dibromo‐9,9‐bis(perfluorohexylethyl propionate) fluorene as the monomers. The fluorinated fluorene copolymers were characterized and investigated via Fourier infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy (1HNMR), ultraviolet absorption spectroscopy (UV–vis), cyclic voltammetry (CV) and photoluminance spectroscopy (PL). Because of the long fluorine‐containing alkyl side chain, the ultraviolet absorption peak of 9,9‐bis(perfluorohexylethyl propionate) fluorene is blue‐shifted compared with poly(9,9‐dioctylfluorene)(PF8). The LUMO energy level increases and the energy band gap of copolymers widens. Due to the self‐assembly of the long fluoroalkyl side chain, the photoluminance spectra of 9,9‐bis(perfluorohexylethyl propionate) fluorene copolymers exhibit a new excimer emission peak at 550 nm. The photoluminance stabilities of the copolymers under irradiation and humid conditions are significantly improved due to protective effect from the long fluoroalkyl side chain. After being irradiated under 500 W iodine tungsten lamp or kept under 70% relative humid conditions, the 9,9‐bis(perfluorohexylethyl propionate) fluorene copolymers showed much better photoluminance stability than that of poly(9,9‐dioctylfluorene) (PF8). These show that introducing long fluoroalkyl side chain into conjugated polymer main chain is a promising strategy to improve environmental stability of devices based on organic conjugated polymers.
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