Intercalation of cyclic imides in kaolinite

The intercalation of two cyclic imides, succinimide and glutarimide, in the interlayer spaces of kaolinite was obtained from a "soft guest-displacement method" by displacing previously intercalated guest molecules. The dimethyl sulfoxide (DMSO)-kaolinite preintercalate was particularly efficient for that purpose. The intercalation exchange was done from a concentrated aqueous solution of the cyclic imides, at ambient temperature, in a relatively short time. Complete displacement of DMSO by the cyclic imides was confirmed by the results of several independent characterizations, including XRD, TG/DTA, FTIR, and C-13 MAS NMR analyses including dipolar dephasing experiments. The imide intercalates are two dimensionally constrained in the kaolinite interlayer spaces, and are Structurally organized in a flattened configuration with their cycle roughly parallel to the ab plane of the kaolinite layers. Elemental analysis gives the following compositions: Al2Si2O5(CH)(4)center dot(C4H5NO2)(0.65) and Al2Si2O5(CH)(4)center dot(C5H7NO2)(0.49), respectively for succinimide and glutarimide. The results of the TG/DTA analyses showed enhanced thermal stabilities of the imide intercalates compared with the starting materials. The intercalation process from the aqueous solution is reversible: in prolonged contact with water, the imide molecules are reLeased, resulting in the rebuilding of the kaolinite structure. These results demonstrate the potential use of kaolinite as a slow-releasing agent for molecules structurally related to the cyclic imides of this study. (c) 2008 Elsevier Inc. All rights reserved.