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 addit ional 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 hy drogen bonded to the S=O group. The other three bands are attributed t o the hydroxyl stretching frequencies of water in the intercalation co mplex. The hydroxyl deformation region is characterized by one intense band in both the FTIR and Raman spectra at 905 cm(-1). Significant ch anges in the Raman spectra of the intercalating molecule are observed. Splitting of the C-H symmetric and antisymmetric stretching vibration s occurs. Two Raman bands at 2917 and 2935 cm(-1) and four bands at 29 99, 3015, 3021, and 3029 cm(-1) are observed. The in-plane methyl bend ing region shows two Raman bands at 1411 and 1430 cm(-1). The DRIFT sp ectra show complexity in these regions. The S=O stretching region show s bands at 1066, 1023, and 1010 cm(-1) upon intercalation with DMSO fo r the low-defect kaolinite and 1058, 1028, and 1004 cm(-1) for the hig h-defect kaolinite. The 1058 cm(-1) band is assigned to the free monom eric S=O group and the 1023 and 1010 cm(-1) bands to two different pol ymeric 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 w ater in the intercalate.