Improved respond speed of thienylene-phenylene electrochromic polymer with pendent double bond structure

A hybrid thienylene-phenylene conjugated molecule with pendent double bond unit on side chain, 5,5'-(2,5-bis (hex-5-en-1-yloxy)-1,4-phenylene)bis (2,3-dihydrothieno [3,4-b] [1,4] dioxine) (EDOT-ene-BE), was designed, and its corresponding polymer poly(EDOT-ene-BE) with similar-network structure was prepared by electrochemical method. The introduction of pendent double bond unit has little influence on the optical absorption and oxidation potential of EDOT-ene-BE. The pendent double bond unit could be attached on polymeric chain of poly (EDOT-ene-BE), leading to linear polymeric chain turning into similar-network structure. The microstructure makes poly(EDOT-ene-BE) film exhibit faster respond speed and higher coloration efficiency than poly(EDOT-BE) without pendent double bond unit. The kinetics indicate that poly(EDOT-ene-BE) could switch between oxidation and reduction states in 0.4 s, which is among one of the fastest respond times. After annealing, the polymerization between pendent double bond units leads to the formation of poly(EDOT-BE-net) with network molecular structure. As poly(EDOT-ene-BE), poly(EDOT-BE-net) possesses faster respond speed relative to poly(EDOT-BE), however, the respond speed is slower than that of poly(EDOT-ene-BE). These results demonstrate that the introduction of pendent double bond unit in side chain results into the formation of similar-network molecular structure, which is proved to be an effective strategy to improve the properties of polymer electrochromic materials.