Investigation of relaxation processes and phase transitions in the silica gel-undecylenic acid system using IR spectra in a wide temperature range

The study of relaxation processes in porous inhomogeneous systems via dielectric and mechanical spectroscopy methods is associated with methodological difficulties. To understand how IR spectroscopy can be used to elucidate the temperature-dependent changes that take place in the undecylenic acid - porous silica gel systems, such as phase transition and relaxation processes, we compare IR spectroscopic data with previously obtained dielectric spectroscopy data for the bulk undecylenic acid and undecylenic acid embedded in silica gel matrices of different pore sizes. We demonstrate that the topological soliton model can be used for both bulk undecylenic acid, and the undecylenic acid in nanoporous silica gel matrices.