N,N,N′,N′- Tetraphenyl-1,4-phenylenediamine-Fluorene Alternating Conjugated Polymer: Synthesis, Characterization, and Electrochromic Application

A novel N,N,N',N'-tetraphenyl-1,4-phenylenediamine (TPPA)-conlaining arornatic dibromide (3), N, N-bis(4- bromophenyl)-N', N'-bis(4-(2.4,4- trimethylpentan-2-yl)phenyl)-1,4-phenylenediamine, was successfully synthesized. The novel conjugated polymer (4) having number-average molecular weight of 2.05 x 10(4) was prepared via Suzuki coupling from the dibromide (3) with 9,9-dioctylfluorene-2,7-diboronic acid bis(1, 3-propanediol) ester. The conjugated polymer (4) exhibited excellent solubility in common organic solvents such as N-methyl-2-pyrrolidinone (NMP), tetrahydrofuran, chloroform, and toluene at room temperature. The conjugated polymer (4) had useful levels of thermal stability associated with their relatively high glass transition temperature (T-g = 144 degrees C), 10% weight-loss temperatures (T-d10) in nitrogen (T-d10 = 445 degrees C),and char yields at 800 degrees C in nitrogen (59.0%). The hole-transporting and electrochronic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammagrams of the conjugated polymer films cast onto indium-tin oxide (ITO)-coaled glass substrates exhibited two reversible oxidation redox couples at E-1,E-2 value of 0.67 and 1.05 V vs Ag/Ag+ in acetonitrile solution, The conjugated polymer film (4) revealed better stability of electrochromic characteristics and more rapid switching time than model polymers N,112 which has no electron-donating bis(4-(2,4,4-trimethylpentan-2-yl) phenyl)amine group and M3 without electron-donating 2,4,4-trimethylpentan-2-yl substituent. The conjugated polymer film (4) also showed high contrast with color change from pale yellowish to green and then to blue at applied potentials ranging from 0.00 to 1.18 V.