Gnatyuk I. Spectroscopy of molecular interactions, dynamics and phase transitions in heterogeneous systems based on alkylcyanobiphenyls

The thesis is devoted to the study of interaction mechanisms between polar molecules of fillers and active centers on the channel surface of inorganic nanoporous matrices dependent on the surface state and external factors, on peculiarities of the ordering and dynamics of these molecules in channels. A set of heterogeneous systems based on silicate porous glasses (pore diameter of 2-90 nm) and alumosilicate molecular sieves of MCM-41 and Me2+MCM-41 (channel diameter of 4 nm) with different types of the surface physicochemical state of channels filled with molecules of the homologous alkylcyanobiphenyls (nCB) row with a different length of the alkyl chain (n=2-9) has been investigated by methods of IR spectroscopy (10000-400 cm-1). For both types of heterogeneous systems distinctions are clearly observed in the behavior of nCB molecules in channels compared to the bulk state. These differences are mainly due to two factors: first of all, the presence of the active surface, and also the influence of the small confining volume. It has been shown that a part of molecules in channels is in a bonded state, interacting with surface active centers by creation of either hydrogen bonds -OH…NєC- or bonds of the coordination type with Me2+. The character and energy of this interaction have been established to depend on the surface pretreatment type. The model of interaction mechanisms between nCB molecules and surface active centers has been proposed. Based on this model the estimation method for the ratio of bulk (free) and bonded nCB molecules has been developed. Results of calorimetric and NMR studies demonstrate that MCM surface active centers are structure defects and lead to the destruction of the nematic and crystal arrangement of nCB molecules in channels. The volume confinement is found out to result in slowing of molecule dynamics of whole molecules, as well as separate molecular groups.