Assembly and Properties Study of Layered Double Hydroxides with UV-shielding Ability
|School||Northeast Normal University|
|Keywords||Layered double hydroxides Intercalation and Assembly UV-shielding capacity Sunscreen|
In this thesis, five organic ultraviolet (UV) ray absorbents, such as mefenamic acid(MFNA), 4,4’-Stilbenedicarboxylic acid (SDCA), 2,4-dimethoxy benzoic acid(2,4-DMOBA), 4,4’-Bis [2-(2-sulfophenyl)ethenyl]biphenyl (CBS-X) and p-methoxycinnamic acid (PMOCA), in their anionic forms, were intercalated into the interlayer space of Mg2Al layered double hydroxides (Mg2Al-LDHs) by co-precipitation method, five organic-inorganic composite UV-shielding materials were obtained. The synthesis and crystallization conditions, chemical composition, structure and property of the products have been studied.After intercalation of these organic ultraviolet (UV) ray absorbents anions, the samples were characterized by XRD, FTIR and UV-vis. The results indicated that the composite materials had typical layered structure and high crystallinity under certain experimental conditions (Mg/Al=2.0, pH≈10.0, Aging Temperature=80℃, Aging Time=24h), the organic UV absorbents still maintained original structures in the interlayer, The interlayer distances were 2.15 nm (LDH/MFNA), 2.09 nm (LDH/SDCA), 1.85 nm (LDH/2,4-DMOBA), 1.93 nm (LDH/CBS-X), and 2.04 nm (LDH/PMOCA), respectively.In addition, this thesis also studied the properties of the intercalated products in complex materials. TG-DTA analysis showed that the composite materials had high thermal stability, the thermal decomposition temperature was above 250℃; the air oxidation reaction for castor oil showed that the oxidation catalytic activity of the composite materials had greatly decreased, even lower than the blank reaction without additives; the UV-Vis transmittance spectra of thin films of the samples demonstrated that all the samples showed excellent UV-shielding ability and transparency in the visible light region.The Mg2Al-LDHs/organic UV absorbents anions, which were easy to prepare in laboratory, had clear chemical composition, excellent UV-shielding ability, high thermal stability and weak catalytic activity. Thus, a new kind of UV-shielding materials had been designed. It would have a vast range of prospect for the development and application in the field of sunscreen.