title: ÐÐ-ÑÐ¿ÐµÐºÑÑÐ¾ÑÐºÐ¾Ð¿Ð¸ÑÐµÑÐºÐ¾Ðµ Ð¸ÑÑÐ»ÐµÐ´Ð¾Ð²Ð°Ð½Ð¸Ðµ ÑÑÑÑÐºÑÑÑÐ½ÑÑ ÑÐ°Ð·Ð¾Ð²ÑÑ Ð¿ÐµÑÐµÑ Ð¾Ð´Ð¾Ð² Ð² Ð½-Ð°Ð»ÐºÐ°Ð½Ð°Ñ
title: Ð²ÑÐ¿ÑÑÐºÐ½Ð°Ñ ÐºÐ²Ð°Ð»Ð¸ÑÐ¸ÐºÐ°ÑÐ¸Ð¾Ð½Ð½Ð°Ñ ÑÐ°Ð±Ð¾ÑÐ° Ð¼Ð°Ð³Ð¸ÑÑÑÐ°
titleType: Subtitle
title: IR spectroscopic study of structural phase transitions in n-alkanes
Creators: name: ÐÑÑÑÐµÐ²Ð°, Ð¡Ð²ÐµÑÐ»Ð°Ð½Ð°
Publisher: name: Ð¡Ð°Ð½ÐºÑ-ÐÐµÑÐµÑÐ±ÑÑÐ³ÑÐºÐ¸Ð¹ Ð¿Ð¾Ð»Ð¸ÑÐµÑÐ½Ð¸ÑÐµÑÐºÐ¸Ð¹ ÑÐ½Ð¸Ð²ÐµÑÑÐ¸ÑÐµÑ ÐÐµÑÑÐ° ÐÐµÐ»Ð¸ÐºÐ¾Ð³Ð¾
Year: 2021
Subjects: Ð¤Ð°Ð·Ð¾Ð²ÑÐµ Ð¿ÐµÑÐµÑ Ð¾Ð´Ñ
Ð¡Ð¿ÐµÐºÑÑÐ¾ÑÐºÐ¾Ð¿Ð¸Ñ Ð¸Ð½ÑÑÐ°ÐºÑÐ°ÑÐ½Ð°Ñ
ÐÑÐ¸ÑÑÐ°Ð»Ð»Ñ Ð¼Ð¾Ð»ÐµÐºÑÐ»ÑÑÐ½ÑÐµ
Ð½-Ð°Ð»ÐºÐ°Ð½Ñ
Ð¼Ð°ÑÐµÑÐ¸Ð°Ð»Ñ Ñ Ð¸Ð·Ð¼ÐµÐ½ÑÑÑÐµÐ¹ÑÑ ÑÐ°Ð·Ð¾Ð¹
ÑÐ¾ÑÐ°ÑÐ¸Ð¾Ð½Ð½ÑÐµ ÑÐ°Ð·Ñ
Ð¼ÐµÐ·Ð¾ÑÐ°Ð·Ñ
n-alkanes
phase change materials
rotator phases
mesophases

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description: The given work is devoted to the kinetics study of the first-order structural phase transition in monodisperse samples of n-alkanes: tricosane Ð¡ââÐââ and tetracosane Ð¡ââÐââ by FTIR spectroscopy. To clarify the relationship between the lamellar structure of n-alkanes and the development of solid-phase transitions, the temperature dependences of the IR spectra were studied in the regions associated with vibrations in the lamella crystal cores and in the interlamellar space. The temperature dependences analysis of the frequencies of methylene Ð¡Ðâ vibration modes in the crystalline lamella cores showed for the first time that the solid-phase transition develops according to a heterogeneous mechanism in ÎÐ¢ ~ 2 K in accordance with the theory of the first-order diffuse phase transition. It is proved that the transition is due to a change in the symmetry type of the initial crystallographic cells of n-alkanes (orthorhombic or triclinic) into hexagonal ones. Additionally, the study of stretching vibrations of C â H bonds made it possible to study the kinetics of the solid-phase transition development in the lamella near-surface regions and to establish the nucleation sources of a new phase depending on the n-alkane parity. Thus, in odd n-alkanes, the initial nuclei of the hexagonal phase are formed in the interlamellar space containing terminal CHâ and closest to them CHâ groups. At the same time, when considering even n-alkanes, it was demonstrated that the transition is generated precisely in the lamella cores. It is shown that the structural phase transition occurs through the formation of a number of intermediate rotator phases (Râ , Râ â , RV), during transitions between which the concentrations of irregular conformers sharply increase: gtg* kinks, gtm end gauche and gg double gauche-defects.