Carbazole based electrochromic polymers with benzoazole units: Effect of heteroatom variation on electrochromic performance

Abstract

A series of carbazole-based polymers were synthesized via Suzuki polymerization between N-(2-ethylhexyl)carbazole- 3,6-bis(ethyleneboronate) (Cbz) and dibromobenzazole unit. Three different polymers, PCBN, PCBS and PCBSe were obtained from 4,7-dibromo-2-hexyl-2H-benzotriazole (BN), 4,7-dibromo-2,1,3-benzothiadiazole-(BS) and 4,7-dibromo-2,1,3-benzoselenadiazole (BSe), respectively. It is observed that, the variation of heteroatoms (N,S and Se) on the benzazole unit have most important effect on electro-optic properties of the PCBX polymers. Neutral state color of the polymer films and their electrochromic performances are also influenced. Among the synthesized polymers, the PCBS bearing 2,1,3- benzothiadiazole as acceptor units has a broad absorption and 50% of ΔT in the near-IR regime at the oxidized state. This property of PCBS is a great advantage for near-IR electrochromic applications.