Synthesis and electrochemical and optical properties of novel poly(aryl ether)s with isolated carbazole and p-quaterphenyl chromophores

Two novel poly(aryl ether)s consisting of alternate isolated chromophores, poly[oxy-[9-(2-ethylhexyl)carbazole-3,6-oxy]-3,3‴-dicyano-p-quaterphenyl- 4,4‴-ylene] (PCNCA) and poly[oxy-[9-(2-ethylhexyl)carbazole-3,6-oxy]-3,3‴-bis(trifluoromethyl)p-q uaterphenyl-4,4‴-ylene] (PCFCA), have been synthesized and characterized. The synthesized polymers are completely soluble in common organic solvents such as tetrahydrofuran (THF) and chloroform. The two poly(aryl ether)s exhibit good thermal stability with 5% weight loss temperature above 400 °C in nitrogen. The UV/vis and photoluminescent spectra of the two polymers show maximum peaks at around 318-319 and 407-413 nm in the film state, respectively. The HOMO and LUMO energy levels of these polymers, which have been measured by cyclic voltammetry, are -5.23, -3.25 eV for PCNCA and -5.41, -3.32 eV for PCFCA. The p-quaterphenyl segments are regarded as electron transporting units because the electron withdrawing substitutes (cyano and trifluoromethyl) enhance the electron affinity. On the contrary, the carbazole segments act as hole transporting units. The two units could decrease the barriers of charge injection from opposite electrodes. Furthermore, all of the two units are emissive chromophores so the photoluminescence (PL) of polymers resulted from the two units. The relative quantum yields of the two polymers are respectively 0.02, 0.40 in film state, and 0.04, 0.19 in THF for PCNCA, PCFCA.