Research Of Changing-Colour And Swelling Capability For Keggin-type Tungstosilicatic Acid Substituted With Vanadium/Poly(Vinyl Alcohol) Composite Materials

Polyoxometalate-based hybrid inorganic–organic materials have not only the advantages of organic materials and of inorganic materials but also their specific properties. These new materials become research hotspot recently and have the possibility of becoming very useful. In this thesis, a series of composite materials containing tungstosilicatic acid with Keggin structure substituted by vanadium/ polyvinyl alcohol (PVA) were prepared. The changed color factors of composite materials were investigated. Swelling property of the PVA composite fibers was researched and discussed.1.PVA composite films and composite fibers, which contained different concentrations of H₅SiW₁₁VO₄₀ and H₇SiW₉V₃O₄₀ were prepared by float-prolonging method and electrospining technique and characterized by Fourier transform-infrared spectroscopy, X-ray diffractometry methods and scanning electron microscopy. The regularity of the fiber materials facies'variability was explained by means of the concentration, viscosity and conductivity of the solution.2.PVA composite films and composite fibers, which contained different concentrations of H₅SiW₁₁VO₄₀ and H₇SiW₉V₃O₄₀ were irradiated under 254 and 365nm ultraviolet light. The photochromism was studied and the reaction mechanism was presented according to electron paramagnetic resonance spectrum. The gather and parting of composite fibers was discovered after the composite fibers were irradiated under, simultaneously the fiber mats turned to thinner. It was supposed that the existing of heteropolyacid was beneficial to the crosslinking of PVA and the occurring of oxidation–reduction reaction.3.PVA composite films and composite fibers, which contained different concentrations of H₅SiW₁₁VO₄₀ and H₇SiW₉V₃O₄₀ were heat-treated under the different temperature and time, then characterized by Fourier transform-infrared spectroscopy, X-ray diffractometry methods and scanning electron microscopy. The heat-chromism was studied and the reaction mechanism was presented according to electron paramagnetic resonance spectrum and Fourier transform-infrared spectroscopy. The fiber materials facies'variability was compared to unheat-treated and the explanation was given.4 . The behavior of swelling of the PVA composite fibers, which contained H₅SiW₁₁VO₄₀ and H₇SiW₉V₃O₄₀ investigated. The effects of polyoxometalate content, structure, heat-treatment temperature and time on the swelling capacity of the PVA fibers were discussed and explained.