Design,Synthesis And Electrochromic Properties Of Asymmetric Viologen Small Molecules/polymers

Compared with inorganic electrochromic materials,organic electrochromic materials have the advantages of strong molecular design,low production cost,easy processing and rich color changes.This makes it widely used in sensors,smart display windows,energy storage and other fields.As an excellent electron acceptor,viologen has become a classic organic electrochromic material due to its multiple redox centers,good redox reversibility,rich color changes and easy-to-adjust chemical structure.In this paper,taking advantage of the easy modification of the structure of viologen,a series of electrochromic viologen small molecules/polymers were designed and synthesized and applied to the field of organic optoelectronic devices.The main contents are as follows.(1)Designed and synthesized asymmetric viologen small molecule compounds for all-solid-state electrochromic devices,and explored in detail the influence of the electronegativity of N-substituents on the performance of electrochromic materials and their devices.Introduce the electron donor group of triphenylamine derivative at the N position of one end of the viologen,and introduce different electron donating groups or electron withdrawing groups at the N position of the other end,Four small asymmetric viologen compounds,Vio-1 ? Vio-4,were designed and synthesized.They are used as active materials to make electrochromic devices.Under the action of an external voltage,the electronic state is changed through an oxidation-reduction reaction,and different color changes can be realized.Among them,compound Vio-1 realized a purple-blue-violet-yellow color transition,with a maximum transmittance change of 50%,and a high color contrast;compound Vio-2 realized a light purple-yellow color transition,with a maximum transmittance change of 20%;compound Vio-3 realized a light purple-light blue-yellow color transition,with a maximum transmittance change of 63%,and high color contrast;compound Vio-4 realized a pink-brown-blue-violet color transition,with transmittance The maximum change is 49%,and the color contrast is high.Experimental results show that the four small asymmetric viologen molecules can be applied to electrochromic display devices and electrochromic tint light glass,and the compound Vio-1 with reversible color change can also be applied to electrochromic switching devices.(2)Fluorene or carbazole-based conductive polymers have the advantages of low cost,processability,high charge mobility,excellent redox properties,high photochemical stability and good electrochromic properties.The side-chain type viologen polymer was synthesized by designing monomers containing viologen unit.The monomers containing viologen units were reacted with fluorene or carbazole monomers through Suzuki coupling reaction to obtain two side-chain type viologen polymers,Vio-K and Vio-W.Among them,the polymer Vio-K can realize the color change of transparent milky white-lilac-gray yellow under the action of electric field stimulation;the polymer Vio-W can realize the color change of transparent milky white-gray yellow.Such polymers are expected to be applied to electrochromic display devices.