Physico-Chemical nanomaterials science

Investigation of the structure and mechanisms of thermal motion in nanostructured undecylenic acid.
K.I. Hnatiuk1, A.N Alekseev1, S.A. Alekseev1, Yu.E. Grabovsky1, M.V. Lazarenko2, M.M. Lazarenko1
1 Taras Shevchenko National University of Kyiv, Physical Faculty, Volodymyrs’ka St. 64/13, Kyiv 01601, Ukraine.
E-mail: email.of. corresponding_author@server.com
2 National University of Food Technologies, Volodymyrs’ka St. 68, Kyiv-01601, Ukraine.

The use of nanomaterials makes it necessary to analyze the basic concepts of condensed matter physics. Such principles are the principle of 2D packaging and the thermodynamics of phase transitions, as well as the mechanisms of thermal motion, which change at the nanoscale.
Little is known about the effect of a porous matrix on the equilibrium and kinetic properties of a substance, as well as on phase transitions in a solid state. The influence of the morphology of pores, in particular the form and chemical composition on these properties, has not been sufficiently studied.
The aim of the work is to study the mechanisms of thermal motion, structure and phase transitions in a nanoscale system of porous silicon and undecylenic acid.
The effect of bounded space of porous silicon nanopores on the structure, thermal motion, and phase transitions in undecylenic acid crystals has been studied. Using thermophysical methods, IR spectroscopy and X-ray diffraction analysis, it was obtained that the temperature of phase transition in the solid state and the melting point decrease. A transition from the orthorhombic crystalline phase in the orthorhombic rotational-crystalline phase in the boundary layer was detected in nanostructured undecylenic acid. Undecylenic acid in the porous silicon matrix and in the bulk sample crystallizes with different subcell, although the long crystal period remains unchanged.
A model of the phase transition in such systems is proposed. This model is associated with the appearance and motion of topological solitons in undecenovy acid.