Preparation And Photochromism Of Layer-by-Layer Self-assembly Hybrid Film Based On Polyoxometalates

Currently, because of its excellent optical characteristics and application value, photochromic composite obtained wide attention from scholars. With high electronic density, multi-valence reversible reduction products and other advantages, related researches about composite materials based on heteropolyacid have gradually developed and matured. Innovative preparation methods continue to emerge, including thin-film technology- the technology allows different types of materials to combine together in accordance with the specific featured need.In this paper,the author uses polyvinylpyrrolidone(PVP) and polyvinyl alcohol(PVA), two kinds of linear polymers, as a substrate and introduces phosphomolybdicacid(PMo A) in to obtain two kinds of photochromic composite film and then studies their photochromic performance. Major elements as followings:Using Layer-By-Layer(Lb L) technology, the phosphomolybdic acid(PMo A) and polyvinyl pyrrolidone(PVP) are combined together through hydrogen bonding interaction to prepare phosphomolybdic acid-polyethylene pyrrolidone composite membrane with good reversibility of photochromic response. UV-vis, FT-IR, AFM, XPS and other means are used to test the structure of phosphorus acid and polyvinylpyrrolidone membrane, and study on the photochromic properties and mechanism. FT-IR and AFM test results show that: phosphomolybdic acid- PVP composite film showed differences in morphology and structure by visible light excitation. And the FT-IR test results show that: the basic Keggin structure of phosphomolybdic acid molecules still exists in phosphomolybdic acid- polyethylene pyrrolidone composite membrane. UV-vis test results show that: phosphomolybdic acid- polyethylene pyrrolidone compound film changed to blue from colorless because of electron transfer. Electrons transfer from PVP to Heteropoly anion, which reduces the phosphomolybdic acid anionic dispersed in polyvinyl pyrrolidone polymer, thus generating heteropoly blue.Using Layer-by-Layer(Lb L) technology, the phosphomolybdic acid(PMo A) and polyvinyl alcohol(PVA) are combined together through hydrogen bonding interaction to prepare the phosphomolybdic acid composite membrane with good reversibility of photochromic response. UV-vis, FT-IR, AFM, XPS and other means are used to test the structure of phosphomolybdic acid polyvinyl alcohol composite membrane, and study on the photochromic properties and mechanism. FT-IR and AFM test results show that: after the visible light, phosphomolybdic acid polyvinyl alcohol composite membranes show differences in morphology and structure. And the FT-IR test results show that: the basic Keggin structure of phosphomolybdic acid molecules still exists in the phosphomolybdic acid polyvinyl alcohol composite membrane.UV-vis test results show that: after the visible light, phosphomolybdic acid polyvinyl alcohol composite membrane changed to blue from colorless because of electron transfer. Electronic transfer from polyacrylamide to Heteropoly anion, which reduces the phosphomolybdic acid anionic dispersed in polyvinyl alcohol polymer, thus generating heteropoly blue.