Nastasienko N. Synthesis and characteristics of ultrafine silica/polyol as components for cryogenic environments

The thesis examines the subject of modification of ultrafine silicas and methyl silicas with polyols, physical and chemical properties thereof and their effects on bull sperm with the goal of improving the cryogenic media with reproductive cells. The silica surface was modified with polyols through adsorption (sorbitol) and impregnation (for all polyols). The data from IR spectroscopy and adsorption experiment results show that the layer of polyols on the surface of silica and methyl silicas forms through interaction of modifier molecules with the silanol groups on the surface of ultrafine silica and formation of surface clusters. Immobilization of polyols on the silica surface is accompanied by inclusion of water molecules into the surface adsorption layer of these carbohydrates. The research demonstrates that the nature of thermolysis of polyols immobilized on the silica depends on the method of immobilization and enables to identify the peculiarities of the structure of the surface layer of polyols. It has been established that modifying silicas through impregnation leads to diminishing contribution of hydrogen bonds to the interaction of polyols with the ultrafine silica surface and greater inclination of these compounds to form surface clusters. It has been demonstrated that the silica- and sorbitol-based composite materials stabilize water domains on their surface which points to possible use of cryoprotectant properties of such composites on cells. The research has investigated the effects of the original ultrafine silicas and methyl silicas, as well as of those modified by the polyols on bull spermatozoa. Also, the research demonstrates the benefits of sorbitol-modified silica as part of cryogenic media for bull gametes.