Intercalation of γ-aminopropyl triethoxysilane (APTES) into kaolinite interlayer with methanol-grafted kaolinite as intermediate

• The structure of intercalation complex transform from bilayer to monolayer was proposed.
• γ-Aminopropyl triethoxysilane is linked to Al–O–CH3 through coordination bond.
• We found the kaolinite plate roll along the b-axis.
• The misfit of the larger tetrahedral and smaller octahedral sheets after intercalation was observed.

γ-Aminopropyl triethoxysilane (APTES) was intercalated into the kaolinite (Kaol) interlayer spaces basing on the wet kaolinite–methanol (Kaol-Me) grafting compound as an intermediate. The Kaol-Me compound was synthesized through guest displacement intercalation reaction of a kaolinite–dimethylsulfoxide (Kaol-DMSO) compound with methanol (Me). The basal spacing was observed in the ranges of 2.36–2.66 nm when Kaol-APTES compounds in toluene-wet state, and 2.01–2.10 nm when Kaol-APTES dried into powder, indicating inhomogeneous intercalation. The XRD patterns for Kaol-APTES, in which APTES was 80 times of the mass of methanol in the wet Kaol-Me compound, suggested that the molecular axis of the amine chains arranged in a bilayer was titled with respect to the Me layers at an angle of 64° in toluene-wet state and in a monolayer angle at angle of 90° in dry-powder state. The APTES molecules were linked to Al–O–CH3 by hydrogen bond. The rolling from platy Kaol into nanotube along the b-axis was observed. High dosage of APTES was found advantageous to the formation of larger basal space and the transformation of the Kaol plate into nanotube. The approximate model of the new intercalate was proposed on the basis of XRD and IR data. The results confirmed the possibility of modification of the kaolinite interlayer surface with APTES at low temperatures with Kaol-Me as intermediate.

Schematic description of the possible reactions between kaolinite and APTES.Figure optionsDownload as PowerPoint slide