| Layered materials are solids with strong in-plane chemical bonds but weak out-of-plane, van der Waals bonds. With such unique structure, layered materials can be exfoliated under some suitable conditions, leading to 2D nanosheets.2D nano materials have many amazing properties that don’t exist in 3D materials, such as high specific surface area, excellent electrical and dielectrical properties, which make 2D materials very promising in catalysator, composite and energy materials, et al. Liquid exfoliation is a ideal way to exfoliate layered materials in large scale with perfect structure. Layered double hydroxides (LDHs)are difficult to be exfoliated due to its high layer charge density and integrated interlamellar hydrogen bonding networks. Up to now, the exfoliation of LDHs in liquid is still under research, seeking for liquid systems that can exfoliate LDHs. Therefore, we choose Mg-Al-LDHs as subject, trying to find out the factors that affect exfoliation from both LDHs and solvents. After this, we use exfoliated LDHs as build unit to synthesize LDHs/polymer composites by emulsion polymerization. The goal this paper is to study the mechanism and law of exfoliation of LDHs, producing a new kind of nanosheet that exfoliated in liquid, and provide a new way of synthesize and design of polymer composites. The major content of this paper are list as follow:1.Coprecipitation method, ion-exchange method, hydrolysis method are adopted to synthesize dodecylbenzenesulfonic ion intercalated LDHs. The structure and component of as prepared products are studied by X-ray diffraction spectrum, X-ray fluorescence spectrum. Its appearance and size are studied by transmission electron microscope, and Thermogravimetric Analysis is used to study its thermal stability. As result turned out, dodecylbenzenesulfonic ion intercalated LDHs are successfully synthesized. LDHs prepared by hydrolysis method has a small Mg/Al mol ratio, leading to higher layer charge density. LDHs prepared by hydrolysis method has the biggest grain size, about 1um. The grain size of LDHs prepared by Coprecipitation method is 200-500nm, and LDHs prepared by ion-exchange method has the smallest grain size, about 100nm.2.The exfoliation of LDHs prepared by three methods in the mixed solvent of styrene and butyl acrylate are studied.The result is confirmed by TEM and atomic force microscopy(AFM).In order to study the relationship between exfoliation and the solubility parameter of solvent, mixed solvents in different proportions are prepared, the exfoliation of LDHs in these solvents are studied. It turned out,LDHs with bigger grain size and higher layer charge density are difficult to be exfoliated. The Polar Solubility Parameter 8 p and the Dispersion Solubility Parameter 8 D of solvent play a big role in the exfoliation of LDHs. When mixed solvent has the right volume proportion of styrene and butyl acrylate (close to 7:3), it has best performance in the exfoliation of LDHs.3.After LDHs is exfoliated in the mixed solvent of styrene and butyl acrylate, sodium dodecyl benzene sulfonate is use as emulsifier, and hexadecanol is used as co-emulsifier to create a stable styrene and butyl acrylate emulsion.LDHs/polymer nanocomposites is prepared by emulsion polymerization. The form and disperse state of LDHs in polymer are studied by XRD. The mechanical properties and thermal stability of as prepared composites are compared with corresponding pure polymer. As is turned out, the completely delaminated LDHs/polymer nanocomposites is successfully synthetized. The addition of LDHs enhance the tensile strength of polymer,and the tensile strength is increase with content of LDHs. Compared to corresponding pplymer, the thermal stability of as prepared composites is barely changed. |
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