Dimethylsulfoxide (DMSO) kaolinite complexes of low-and high-defect kaolinites were studied by thermo-IR-spectroscopy analysis.
Samples were gradually heated up to 170°C, three hours at each temperature. After cooling to room temperature, they were pressed
into KBr disks and their spectra were recorded. From the spectra two types of complexes were identified. In the spectrum of
type I complex two bands were attributed to asymmetric and symmetric H-O-H stretching vibrations of intercalated water, bridging
between DMSO and the clay-O-planes. As a result of H-bonds between intercalated water molecules and the O-planes, Si-O vibrations
of the clay framework were perturbed, in the low-defect kaolinite more than in the high-defect. Type II complex was obtained
by the thermal escape of the intercalated water. Consequently, the H-O-H bands were absent from the spectrum of type II complex
and the Si-O bands were not perturbed. Type I complex was present up to 120°C whereas type II between 130 and 150°C. The presence
of intercalated DMSO was proved from the appearance of methyl bands. These bands decreased with temperature due to the thermal
evolution of DMSO but disappeared only in spectra of samples heated at 160°C. Intercalated DMSO was H-bonded to the inner-surface
hydroxyls and vibrations associated with this group were perturbed. Due to the thermal evolution of DMSO the intensities of
the perturbed bands decreased with the temperature. They disappeared at 160°C together with the methyl bands.