Phase transitions

Specificity of the transformation of end methyl groups in the interlamellar regions of tetracosane during the solid-solid phase transition as revealed by FTIR spectroscopy

V. A. Marikhin^a, S. A. Gur'eva^a, E. N. Vlasova<sup>b

a</sup> Ioffe Institute, St. Petersburg, Russia
^b Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia

Abstract: The kinetics of the development of the first-order diffuse structural phase transition in monodisperse samples of tetracosane C$_{24}$H$_{50}$ was studied by FTIR spectroscopy. The temperature dependences of the frequencies and intensities of the C–H-stretching vibrations in the spectral region $\nu$ = 2800–3000 cm$^{-1}$ were studied for 4 different modes in the methylene CH$_2$ trans sequences of the main chain and for 4 different modes corresponding to the end methyl CH$_3$-groups. Specific changes in the vibrational frequencies of all investigated modes are found, which are caused by changes in the symmetry of the molecular packing during the first-order phase transition.

Keywords: n-alkanes, phase transitions, theory of diffuse phase transitions, IR spectroscopy.

Received: 23.08.2022
Revised: 23.08.2022
Accepted: 25.08.2022

DOI: 10.21883/FTT.2022.12.53659.462

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