Electrochromic polymer with asymmetric substituents – Inhibit aggregation and modify respond speed

• An electrochromic polymer with asymmetric substituents was prepared. • Asymmetric polymer exhibits different film morphology structure from symmetric polymers. • The relationship between molecular aggregation and electrochromic properties is discussed. The asymmetric structure could improve the electronic properties of molecules through changing the molecular packing style. In this paper, a conjugated molecule EDOT-BE-1 F (5,5′-(2-fluoro-5-(hexyloxy)-1,4-phenylene)bis(2,3-dihydrothieno[3,4–b] [1,4]dioxine)) was constructed based on the asymmetric chains (hexoxyl group and fluorine atom) para -substituted para -phenylene, and polymerized to poly(EDOT-BE-1 F ) by electrochemical method. The asymmetric chains endow molecule possess compromised configuration, making poly(EDOT-BE-1 F ) display different film morphology, hydrophobic property and molecular aggregation from symmetric polymers. The electrochromic result demonstrate that the asymmetric poly(EDOT-BE-1 F ) could achieve color change between red and blue with the fast respond time (0.9 s) and high coloration efficiency (305C −1 cm 2 ). Through the comparison of asymmetric poly(EDOT-BE-1 F ) and symmetric poly(EDOT-BE- O ), we found the decreased molecular aggregation has positive influence on respond speed and coloration efficiency of polymer during reduction process, however, displays no obvious help on that of polymer during oxidation process. The relationship between molecular aggregation and electrochromic properties of conjugated polymer is discussed in detail. The result prove that the asymmetric chains could effectively modify the molecular aggregation and balance the charge transport and ion migration, which provide a simple method to modify the performance of polymer.