Azizova L. Adsorption and thermal transformations of aliphatic carboxylic acids, heparin and muramyl dipeptide on the silica and alumina surfaces

The thesis is devoted to the studying of the interaction of carboxyl group containing compounds (aliphatic carboxylic acids, heparine and muramyl dipeptide) with the surface of fumed silica and alumina. The adsorption of linear and branched aliphatic carboxylic acids C1-C6 on the fumed silica surface and the adsorption of valeric acid on the surface of alumina have been studied. Valeric acid sorption capacity of Al2O3 is three times higher than that for silica. The formation of different types of surface complexes of carboxylic acids on the silica surface using IR spectroscopy, DTG, temperature programmed desorption mass spectrometry (TPD MS) methods has been determined. Their relative amount and activation energy of desorption from the surface have been calculated by means of TPD MS. The mechanism of ketene formation on the silica surface has been suggested. The correlation between hydrophobicity parameter lgPo/w and the ratio of peaks intensities of complex distruction on the TPD curves has been obtained. Kinetic parameters of ketene formation by reaction of carboxylic acid over Al2O3 have been calculated by TPD MS. The hydrolytic stability of grafted ester groups of carboxylic acids on the silica surface has been studied by means of TPD MS. Thermolysis stages have been identified, kinetic parameters have been calculated and mechanisms of thermal transformation of the aglycone, the peptide fragment and the carbohydrate moiety of O-glycoside of muramyl dipeptide (MDP) using TPD MS have been proposed. Using IR-spectroscopy and TPD MS it has been shown that the adsorption of MDP on the silica surface occurs due to carboxylic and -NH groups of isoglutamine not involved in the formation of hydrogen bonds, stabilizing beta-turns. Thermolysis stages of heparin in the pristine state and adsorbed on the silica surface have been identified. It has been shown by means of photon correlation spectroscopy and scanning electron microscopy that the surface modification of silica with heparine causes changes in particle size distribution.