Synthesis and Electroluminescent Properties of Polyfluorene-Based Conjugated Polymers Containing Bipolar Groups

A bipolar dibromo monomer, bis-(4-bromophenyl)[4-(3,5-diphenyl-1,2,4- triazole-4-yl)-phenyl]amine (9), containing electro-rich triphenylamine and electrodeficient 1,2,4-triazole moieties was newly synthesized and characterized. Two fluorescent fluorene-based conjugated copolymers (TPAF, TPABTF) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7-dibromo-2,1,3-benzothiadiazole (BTDZ), and 9,9-dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (Tg) higher than 135°C and 5% degradation temperatures in nitrogen atmosphere were higher than 428°C. Single layer polymer light-emitting diodes (PLED) of ITO/ PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF. The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn-on voltage of 5 V, a maximum electroluminance of 696 cd/m2, and a peak efficiency of 2.02 cd/A. © 2009 Wiley Periodicals, Inc.