Carbazole Functionalized Star Shaped Triazine Monomer and Its Electrochromic Applications

A new star shape monomer, 2,4,6-tris((9H-carbazol-2-yl)oxy)-1,3,5-triazine (CTR) was synthesized. It was electrochemically polymerized in boron trifluoride diethyl etherate (BFEE)/acetonitrile (ACN) solvent couple. The interaction between BFEE and the CTR lowers the oxidation potential of the monomer and the catalytic effect of BFEE facilitated the formation of high quality polymer film. Electrochemically prepared P(CTR) film was characterized via CV, SEM, FTIR, TGA and UV-vis spectroscopy. Spectroelectrochemical analysis revealed that P(CTR) has high band gap energy which provide it colorless in the neutral state. Electronic transitions of the P(CTR) were observed at 327 and 650 nm, revealing π to π * transitions, and polaron band formation. The polymer switches between dark turquoise and transparent with a switching time of 1.5 s and an optical contrast (%ΔT) of 50%. Electrochromic studies revealed that P(CTR) has opposite properties to EDOT in terms of redox color. In addition to a dual-type complementary colored polymer electrochromic device based on P(CTR) and P(EDOT) was constructed in sandwich configuration. Spectroelectrochemical studies disclosed that the oxidized state of the device shows a blue color and it is transparent in the reduced state. Switching time and maximum contrast (%ΔT) of the device was measured as 3 s and 32% for 615 nm.