Surface Properties Of Organic-inorganic Hybrids Based On LDHs Characterized By Inverse Gas Chromatography

Layered doubled Hydroxides （MgAl, ZnAl, CuMgAl） were synthesized byco-precipitation, MgAl-LDHs and ZnAl-LDHs were modified by sodiumdodecylesulfonate （SDS） and silane coupling agent （KH570, KH550, KH151） toobtain organic-inorganic hybrids, which include intercalated modification materials,ostensible modification materials, and intercalated-ostensible modification materials.The propertie of such materials has been characterized by inverse gas chromatography（IGC）. The effect of organic modification on the propertie of LDHs was investigated.The stability and acid-alkali capacity of CuMgAl-LDHs were also dissgussed. Themechanism on synthesization of hybrids was presumed in virtue of computersimulation.The results show that:Measurement of XRD, FTIR, TG and DTA indicate that SDS had been adoptedin the interlayer of MgAl-LDHs, KH570had condensed with the hydroxyl groups onthe hydrotalcite surface, KH570-SDS-LDHs which was intercalated-ostensiblemodification materials, was most stable and hydrophobe of all samples. IGC analysisindicate γS^Dvalue of KH570-SDS-LDHs was minimum,17.49mJ m^-2at433K. γS^Dofhybrids decreased while the temperature increased, this indicate that enhancetemperature could be one way to improve the compatibility between LDHs andpolymer, when polymer/LDHs nanomaterials was synthesized. Acid-alkali capacity ofLDHs and hybrids has been characterized qualitatively, surface alkalescencedecreased after modified. KH570-SDS-LDHs had the stongest interaction and best affinity with organics, because hydrophobic surface of SDS-LDHs could adsorbeKH570easily, which result in mantled hydroxyl site nearly all.Results of XRD,FTIR and computer simulation on the intercalation of SDS intoZnAl-LDHs, the mechanism on synthesization of hybrids was presumed, SDS insolution exchanged with NO₃^-on the edge of the layer, SDS diffused in theinterlamination, then exchanged with NO₃^-in the interlamination, NO₃^-occupied theedge, SDS in solution exchanged with NO₃^-on the edge of the layer continuely,ultimately SDS arranged in the interlayer by monolayer perpendicularly, silanecoupling agent covered the surface of LDHs by condensing with hydroxyl groups onthe hydrotalcite surface. IGC analysis indicates γS^Dof KH151-SDS-LDHs andKH550-SDS-LDHs were close, this may due to the close length of carbonchains.Acid-alkali capacity of LDHs and hybrids has been characterized quantificationally,based on the acid and base parameter, SDS-LDHs trend to be amphoteric,KH151-SDS-LDHs and KH550-SDS-LDHs are slightly basic.FTIR and IGC of analysis on CuMgAl-LDHs show that, surface free energy andthe dispersive component of the surface energy increased, with increasing amounts ofCu²⁺, then the chemical stability of the system became worse, which was consistentwith the outcome of computer simulation, this may attribute to Jahn-Teller distortionof Cu²⁺effect stability of brucite-like layers. Acid-alkali capacity of CuMgAl-LDHshave been characterized qualitatively, surface alkalescence decrease originally, thenincrease with increasing amounts of Cu²⁺.