Preparation And Photochromism Of Inorganic-Organic Hybrid Film Based On Polyoxometalates

From the first proposed photochromic phenomenon was more than a century,with in-depth study of photochromism principle,types and applications had been greatly expanded,including heteropoly acid based on photochromic materials because of its absorption spectrum across the ultraviolet region and visible region and get more attention.Miscellaneous polyoxometalate based on composite materials to show its potential.In this paper,inorganic organic composite films were prepared by combining polypyrrole?PPy?,polyaniline?PANI?and polythiophene?PTh?as three polymer substrates and combined with phospho molybdate acid?PMoA?.The photochromic reaction of composite films was studied,analyzed and determined.PMoA/PPy composite films,PMoA/PANI composite films and PMoA/PTh composite films were prepared by dropping film method.The property of surface morphology before and after visible-light irradiation and compounding,structure change,element composition and valence state change of the composite films were analyzed by AFM,FT-IR UV-vis and XPS test apparatus.By analyzing the interaction between heteropoly acid and polymer substrate,energy level transition and charge transfer mechanism,the mechanism of light to discoloration was studied.The three groups of experimental contents were analyzed as follows:1.For PMoA/PPy inorganic-organic composite film,the basic morphology of heteropoly acid and polymer changed before and after illumination.The composite film is irradiated by visible light,and the color changes from colorless to blue.When vacuum or nitrogen was added,the composite film does not fade.In the presence of oxygen,the composite film begins to fade from blue to colorless,and oxygen plays a decisive role in the fading reaction,and the photochromic process was carried out according to the proton transfer mechanism.2.For PMoA/PANI inorganic-organic composite film,the basic structure of polypyrrole polymer and phosphomomomo acid in Keggin structure were found in the composite film by infrared spectroscopy.The analysis results of AFM showed that the basic morphology of the heteropoly acid and the polymer before and after the light is changed,and the ultraviolet spectrum is used to study the discoloration.The process of photoelectron transfer is studied by XPS.Under the irradiation of visible light,the composite membrane changed from colorless to blue,producing heteropoly blue.The oxygen played a decisive role in the reaction,and the photochromic process was carried out according to the proton transfer mechanism.3.For PMoA/PTh composite film,the basic morphology of heteropoly acid and polymer changed before and after illumination.The composite film was irradiated by visible light,and the color changes from colorless to blue.In the presence of oxygen,the composite film begins to fade from blue to colorless,and oxygen plays a decisive role in the fading reaction,During the period,Mo⁺⁶ were reduced to Mo⁺⁵,and Mo⁺⁵were oxidized to Mo⁺⁶ under the condition of oxygen.This was due to the reversible photochromic reaction produced by the proton transfer mechanism between polypyrrole and phospho molybdate.