Molecular structure of dimethyl sulfoxide intercalated kaolinites

Upon the intercalation of kaolinite with DMSO, new Raman bands at 3660, 3536, and 3501 cm(-1) are observed for the low-defect kaolinite and at 3664, 3543, and 3509 cm(-1) for the high-defect kaolinite. An additional band at 3598 cm(-1) was observed for the high-defect kaolinite. The band at 3660 cm(-1) was assigned to the inner-surface hydroxyls hydrogen bonded to the S=O group. The other three bands are attributed to the hydroxyl stretching frequencies of water in the intercalation complex. The hydroxyl deformation region is characterized by one intense band in both the FTIR and Raman spectra at 905 cm(-1). Significant changes in the Raman spectra of the intercalating molecule are observed. Splitting of the C-H symmetric and antisymmetric stretching vibrations occurs. Two Raman bands at 2917 and 2935 cm(-1) and four bands at 2999, 3015, 3021, and 3029 cm(-1) are observed. The in-plane methyl bending region shows two Raman bands at 1411 and 1430 cm(-1). The DRIFT spectra show complexity in these regions. The S=O stretching region shows bands at 1066, 1023, and 1010 cm(-1) upon intercalation with DMSO for the low-defect kaolinite and 1058, 1028, and 1004 cm(-1) for the high-defect kaolinite. The 1058 cm(-1) band is assigned to the free monomeric S=O group and the 1023 and 1010 cm(-1) bands to two different polymeric S=O groups. Bands attributed to the C-S stretching vibrations, the in-plane and out-of-plane S=O bending and the CSC symmetric bends all move to higher frequencies upon intercalation. It is proposed that intercalation with DMSO depends on the presence of water and that the additional bands at 3536 and 3501 cm(-1) are due to the presence of water in the intercalate.