Study On The Preparation And Photochromic Properties Of Inorganic/Organic Hybrid Films Containing Polyoxometalate

Photochromic composite materials with good light sensitivity and extensive applications are being paid more and more attentions.Polyoxometalates become promising candidates because of their intriguing capability for reversible multivalence reduction,forming mixed-valence species,which makes them suitable for photochromic and electrochromic materials.In order to realize practical application in the technological fields,the considerable attention has been focused on the study of polyoxometalates nanoparticles dispersed into polymeric networks to obtain transparent nanocomposites thin films.In this paper,two crosslinked polymers were prepared based on N-vinylpyrrolidone and N,N'-methylene-bis-acrylamide, N-vinylpyrrolidone(VP) and bisvinyl-A(BVA) respectively.And they were used as polymer matrix to construct novel photochromic nanocomposite thin films with entrapping the Keggin-type polyoxometalates.Also,a photochromic nanocomposite thin film was prepared based on polyacrylamide(PAM) and Keggin-type molybdenumphsophoric acid(PMoA).All the films showed good structure and photochromic character.The main results are outlined as following:A crosslinked polymer(P(VP-MB)) was prepared based on N-vinylpyrrolidone and N,N'-methylene-bis-acrylamide,the Keggin structure heteropolyacid(POM) (M=W,Mo) is introduced into the P(VP-MB) polymer network,Under ultraviolet light the composite film change from colorless into the blue,heteropolyacid has been deoxidized to heteropolybules.The whole reduction is in accordance with the mechanism of the charge transfer.The bleaching process of the composite films took place in air.Compared with PWA/P(VP-MB) film,PMoA/P(VP-MB) film showed quicker response under UV and lower bleaming process.A crosslinked polymer P(VP-BVA) was prepared based on N-vinylpyrrolidone and bisvinyl-A(BVA),the Keggin structure heteropolyacid(POM)(M=W,Mo) is introduced into the P(VP-BVA) polymer network,Under ultraviolet light the composite film change from colorless into the blue,heteropolyacid has been deoxidized to heteropolybules.The whole reduction is in accordance with the mechanism of the charge transfer.The bleaching process of the composite films took place in air.Compared with PWA/P(VP-BVA) film,the PMoA/P(VP-BVA) film had higher photochromic efficiency and slower bleaching reaction.An other photochromic nanocomposite film was prepared based on polyacrylamide(PAM) and Keggin-type molybdenumphsophoric acid(PMoA) through LBL technique.Under ultraviolet light the composite film change from colorless into the blue,heteropolyacid has been deoxidized to heteropolybules.The whole reduction is in accordance with the mechanism of the charge transfer.The film showed good photochromic effect.