Preparation And Performance Study Of Electrochromic Materials Containing Triarylamine Structural Units

Electrochromism is known as the alternation of color by the application of a potential.This interesting property has led to many technological applications such as smart windows,automatic antiglazing mirrors,large-scale electrochromic screens,and chameleon materials.In this paper,we synthesized a series of polyimides(PIs)and polyazomethines containing triphenylamine,and explored their electrochromic,properties.The structures of polymers were characterized by means of FTIR,1H NMR spectroscopy,which showed an agreement with the proposed structure.Most of them exhibited NIR electrochromic characteristics with promising applications.The aromatic polyimides(PIs)have been synthesized by a conventional two-step polymerization process.All polyimides displayed outstanding thermal stability and high char yields.In addition,the polymer films showed reversible electrochemical oxidation,high coloration efficiency(CE),low switching time,and anodic green electrochromic behaviors.The polymer films revealed excellent stability of electrochromic characteristics for the radical cations generated,changing color from original yellowish to green(red)and blue in range of Uv to NIR.The poly(N-phenylbenzylamines)(RPAMs)have been synthesized by the reduction of polyazomethines(PAMs).Thermogravimetric analysis(TGA)showed that all the RPAMs were stable,with 5%weight losses recorded above 353 ? in nitrogen atmosphere.All the polymers are readily soluble in CHCl3,THF,DMF and DMAc.The RPAMs exhibit a strong blue-green fluorescence with a maximum at 415-514 nm,and the fluorescence quantum yield of RPAM-a in THF is about 18%.The PL intensity and color of the RPAMs changed depending on the value of pH.The highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)energy levels of these polymers were determined in the range of-4.51--5.03 and-1.58--2.33 eV(vs.the vacuum level)by cyclic voltammetiy method consistent with the results of quantum chemical calculation.The polymer films revealed excellent stability of the electrochromic characteristics,with a color change from neutral pale yellowish to a purple doped form at applied potentials ranging from 0.0 to 1.5 V.The RPAMs showed a typical photovoltaic response and the SEM images implied the RPAM would be inclined to self assemble into ball particles.The properties prove that the polymers in this paper are multipurpose materials which will be subject of hole-transporting,electrochromic,chemical sensor application in near future.