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 SO 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 SO 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 SO group and the 1023 and 1010 cm-1 bands to two different polymeric SO groups. Bands
attributed to the C−S stretching vibrations, the in-plane and out-of-plane SO 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.
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