Study On Preparation And Optical Characteristics Of Polymer/inorganic Nanocomposite Film

Using zirconium n-butoxide as the precursor of zirconia,PMMA and PSt as the polymer matrixes,two coating sols have been successfully prepared from PMMA and PSt with zirconium n-butoxide in different molar ratios by the hydrolytic sol-gel technique, respectively.The PMMA/nano-ZrO₂ and PSt/nano-ZrO₂ composite films have been fabricated by the dip-coating or casting followed by the mild thermotreatment, respectively.The structure and transmission,photoluminescence,thermal stability and surface morphologies of two composite films with different ZrO₂ loading have been characterized by the X-ray diffraction(XRD),Fourier transformation infrared(FTTR), ultraviolet-visible spectrophotometry(UV-Vis),fluorescence,thermogravimetric analysis (TGA)and field emission scanning electron microscope(FESEM)and transmission electron microscopy(TEM)techniques.The XRD results showed that the Zr in the resulting composites is the form of the monoclinic ZrO₂.The results of FTIR and solvent treatment experiments displayed that there are the partial covalent bond interactions between the inorganic ZrO₂ and polymer chains in the composites.From the cross-sectional and surface FESEM observation a good contact between the polymer matrix and zirconia can be found,the monoclinic ZrO₂ particles were uniformly dispersed within the polymer matrix,and no macroscopic voids were found in the membrane matrix when the ZrO₂ content is less than 10%for the PMMA/ZrO₂ and 3%for the PSt/ZrO₂. After the incorporation of the nano-ZrO₂,the transmittance and thermal stability of the composites increased,and in particular,the photoluminescence properties significantly enhanced.In addition to this paper,a photochromic composite(CMC/PW₁₂)was prepared from carboxymethyl cellulose(CMC)and phosphotungstic acid(PW₁₂)as well as a composite (MC/PMo₁₂)consisting of methyl cellulose(MC)and phosphomolybdic acid(PMo₁₂) was formed in solution,respectively.The structures and photochromic properties of the photochromic composite(CMC/PW₁₂)and the photochemical reaction mechanism for the MC/PMo₁₂composite were investigated by the FTIR,XRD,UV-Vis,electron resonance spectroscopy(ESR),cyclic voltammetry(CV)and TGA,respectively.It was found that the Keggin structure of the heteropoly acid in the composite films was not destroyed.The charge transfer between the polymer chain and heteropoly anion occurred under the UV irradiation.As a result,the partial hydroxyl groups of polymers in the composites were oxidized into the carbonyl groups and the W(â…¥)and Mo(â…¥)were reduced into the W(â…¤) and Mo(â…¤),respectively,causing the color of the composites were changed from colomess to blue.The photochromism for the CMC/phosphotungstic acid composite film was reversible and for the MC/phosphomolybdic acid composite in the form of aqueous solution and film and was irreversible.