| Electrochromic materials(ECM)are one of functional materials,which have very bright application future.It can be used widely in military camouflage,screen display,information storage,smart window and so on.As one of excellent ECM with the outstanding properties,such as low cost,multicolored,tunable ability,and good stability,viologen compounds have become one of the hot spot of current research.But the research of viologen in the domestic is still in its infancy.In this paper,we have synthesized five small molecule symmetric viologen compounds and four symmetric viologen polymers by reaction between halogenated hydrocarbon and 4,4’-bipyridine,and the synthesis conditions are optimized,the structure of the compounds were characterized and the electrochromic properties are investigated.1.The synthesized viologen compounds show two obvious pairs of redox peak,and the reaction processes are not diffusion-limited quasi-reversible process;the first oxidation potential Epal of alkene substituted viologen compounds increases toward the positive direction with the growth of the carbon chain length,the Epal of benzyl substituted viologen is lower than that of the alkene substituted viologen;2.Colorimetric analysis was used to study the color change of viologen compounds.It is found that chromatic aberration of alkene substituted viologen compounds became smaller with alkyl chain becoming longer;the chromatic aberration of viologen polymer was superior to the corresponding small molecule viologen;3.The square wave testing shows that with the increase of the carbon chain length,the response time of alkene substituted viologen compounds became shorten and the maximal contrast decreased;but compared with the corresponding small molecule viologen,the bleaching speed of viologen polymer was faster,the coloring speed became slower and the maximal contrast has only small change;4.The cycle life of alkene substituted viologen compounds become longer when the carbon chain length increases;the benzyl substituted viologen has a medial stability comparing with the alkene substituted viologen compounds;small molecule viologens have longer cycle life than corresponding viologen polymer. |
