Interlamellar amino functionalization of kaolinite

Abstract

The interlamellar surface of kaolinite has been modified with molecules possessing amino functionalities. Either the dimethyl sulfoxide intercalate of kaolinite (Kao/DMSO) or the N-methylformamide intercalate of kaolinite (Kao/NMF) were used as starting materials. One of the products, an ethanolamine functionalized kaolinite (Kao–EOA) was resistant to thermal decomposition in both air and N2 atmospheres up to temperatures greater than 150 °C. Based on results from thermal analysis, IR analysis, 13CCP/MAS NMR spectroscopy, and elemental analysis, a structural model is proposed in which every third interlayer surface hydroxyl group on the aluminol (Al-OH) surface of kaolinite is either replaced with an interlayer Al-OCH2CH2NH2 group or is strongly H-bonded to an aminoalcohol molecule. A mixture of both types of linkages could coexist. The amino groups that point away from this surface are each keyed into the -(SiO−)6 macro-rings of the adjacent silicate surface, resulting in an amino-functionalized ordered two-dimensional organo-mineral assembly. Keywords: kaolinite, halloysite, organo-mineral nanocomposites, clay functionalization, supramolecular assemblies.