Assembly And Structural Characteristics Of UV Absorbents Pillared Layered Double Hydroxides

In the thesis, five organic UV absorbents, such as mefenamic acid, 4,4'-Bis [2-(2-sulfophenyl)ethenyl]biphenyl, 4,4′-[1,4-phenylenebis(methylene)] bis (azanediyl)dib- enzoic acid, 4,4′-[1,3-phenylenebis(methylene)] bis (azanediyl)dibenzoic acid, 2,4-dimeth- oxy benzoic acid, in their anionic, has been intercalated into a layered double hydroxide (LDHs) host by coprecipitation method. Five organic-inorganic composite materials, Zn2Al-LDH/MFNA, Zn2Al-LDH/1,4-PMBADA, Zn2Al-LDH/1,3-PMBADA, Zn2Al-LDH/C BS-X and Zn2Al-LDH/SDCA were obtained. Products obtained were characterized by X-ray diffraction (XRD), FT-IR, UV-Vis, TG-DTA. Thermal stability, UV shielding ability, catalytic activity for the air of castor oil and chemical stablility of the composite materials were investigated.The results indicated that synthetic products with high crystallinity, single crystal phase, clear chemical composition in control of the experimental condition (Zn/Al=2.0, pH 8.6-9.0, Aging Temperature=80℃, Aging Time=24h). XRD patterns showed that the basal spacing of Zn2Al-LDHs were greatly expanded as 2.01 nm (Zn2Al-LDH/MFNA), 1.85nm (Zn2Al-LDH/1,3-PMBADA), 2.14 nm (Zn2Al-LDH/1,4-PMBADA), 2.09 nm (Zn2Al-LDH/SDCA) and 1.97 nm (Zn2Al-LDH/CBS-X), respectively. Organic UV absorbents still maintain original structures in the interlayer arranged orderly in the form of single-or double-staggered .According to the UV-Vis transmittance spectra of thin films of the samples, all Zn2Al-LDHs/organic UV absorbents showed excellent UV-shielding ability and transparency in the visible light region. When intercalated into LDHs, their UV absorption were improved.The air oxidation of castor oil showed that the organic UV absorbents pillared LDHs almost have no oxidation catalytic activity. TG-DTA analysis showed that the composite materials had well thermal stability, Organic anions between layers achieve the decomposition temperature above 400℃.Coprecipitation method is a simple and effective method for assembly of UV absorbents pillared LDHs. All Zn2Al-LDHs/organic UV absorbents showed excellent UV-shielding ability and transparency in the visible light region; low oxidation catalytic activity; well thermal stability. As new generation of UV absorbing materials, in the area of cosmetics and polymeric materials have a wide application prospect.