Study On The Delamination Mechanism Of Mg-Al Layered Double Hydroxides In The Solvent

Two-dimensional nanomaterials(2D nanomarterials)have unique chemical,electrical and mechanical properties due to their nano-effect and high specific surface area.Therefore,they are widely used in many fields such as catalyst,photochemistry,energy storage and medical carrier and so on.The layered materials(LMs)are defined as solids with strong in plane chemical bonds but weak out of plane,van der Waals bonds.LMs can be exfoliated into the 2D nano-sheets in liquid phase,which make them an important source of 2D nanomaterials.Layered double hydroxides(LDHs)are an only class of anionic clays consisting of positive charged brucite-like layers and interlayer anions.With high density positive charge,hydroxide layers are connected by strong electrostatic interactions with interlayer exchangeable anions,which make it difficult to be delaminated into 2D materials.At present,the studies on the exfoliation mechanism of LDHs mainly focus on the interlayer structure and interaction between layers.However,few reports concern the LDHs delamination from the point of view of solvents.At the same time,owning to the difficulty to be delaminated for LDHs,there is relatively lack of the research systems on completely exfoliated LDHs/polymer nanocomposites.Therefore,the Mg/Al-LDHs were chose to study the relationship between the LDHs layer and the mixed solvents or pure solvents in this thesis.Moreover,an attempt was made to prepare LDHs/ co-polymer of styrene(St)and BA(butyl acrylate)nanocomposites from the emulsion composed of delaminated LDHs and the mixed solution of St/BA at the proper ratio.The main contents of this thesis are listed as follows:1.Sodium dodecyl sulfate anion(SDS)intercalated Mg/Al-LDH(Mg/Al-LDH-SDS)was synthesized via co-precipitation method.Delamination of Mg/Al-LDH-SDS was investigated in the mixed solvents of St/BA with different proportions and selected pure solvents.The delamination mechanism of Mg/Al-LDH-SDS in the mixed solvents is proposed based on the discussions of Tyndall phenomenon,the effects of surface tension of solvents and their contact angles on Mg/Al-LDH-SDS delamination,and on the calculation and tests on solubility parameters of Mg/Al-LDH-SDS in the St/BA mixed solvents.2.After preparation by the co-precipitation method,Mg/Al-LDH-SDS was dispersed in terpineol and the delamination process was observed.An expansion phase of Mg/AlLDH-SDS intercalated by solvent molecules was found for the first time with basal spacing 3.5311 nm.The delamination mechanism of Mg/Al-LDH-SDS in terpineol was confirmed by the characterization results of ultraviolet absorption spectrum,X-ray diffraction(XRD),scanning electron microscopy(SEM)and atomic force microscopy(AFM).3.Via the co-precipitation method,dodecyl benzene sulfonic ion(SDBS)intercalated Mg/Al-LDH-SDBS was synthesized.The delamination solution of LDHs with high concentration was obtained in the mixed solvent of St/BA.Dodecyl benzene sulfonate was selected as emulsifier with hexadecanol as co-emulsifier to prepare miniemulsion.Azodiisobutyronitrile(AIBN)was used as initiator.The stable composite latex was obtained after polymerization.The composite of LDHs/co-polymer of St and BA(poly(St-co-BA))was produced by centrifugation and washing.The structure and properties of LDHs/poly(St-co-BA)nanocomposites were characterized by XRD,SEM,transmission electron microscopy(TEM),thermal gravity analysis(TG)and mechanical testing.