Molecular Structure of Dimethyl Sulfoxide in DMSO-Intercalated Kaolinites at 298 and 77 K

The molecular structure of dimethyl sulfoxide at liquid nitrogen temperature has been obtained from the Raman spectra of dimethyl sulfoxide intercalated kaolinites by the use of Raman microprobe and a low temperature thermal stage. Raman bands at 2917 and 2935 cm -1 for the symmetric stretching and four bands at 2999, 3015, 3021, and 3029 cm -1 for the antisymmetric stretching are observed at 298 K. At liquid nitrogen temperature, five symmetric stretching frequencies at 2882, 2907, 2917, 2920, and 2937 cm -1 and six antisymmetric stretching frequencies at 2986, 2994, 3000, 3012, 3023, and 3032 cm -1 are observed for the DMSO-intercalated low defect kaolinite. Differences in the position and number of bands are observed for DMSO between the DMSO-intercalated low and high defect kaolinites. The in-plane methyl-bending region shows two Raman bands at 1411 and 1430 cm -1 at 298 K and 1411 and 1426 cm -1 at 77 K. The S O stretching region shows bands in the 298 K spectra at 1066, 1023, and 1010 cm -1 and at 1010, 1023, and 1062 cm -1 in the 77 K spectra. These bands are assigned to the free monomeric S O group and two different polymeric S O groups. The C−S vibrations also show increased complexity upon obtaining spectra at 77 K. The additional bands of DMSO are attributed to the different molecular structures of DMSO in the DMSO-intercalated kaolinites.