engleski

EPR study of solid ethanol

The study of glass-forming materials represents a challenge in various scientific fields [1]. Due to the large number of minima in the potential energy surface glassy state shares a fundamental property with proteins in the sense of existence of nearly isoenergetic conformational substates [2]. In this context solid ethanol offers the possibility to study molecular dynamics in phases characterized by different types of disorder which results from a controlled thermal history of the sample. In this contribution we show how electron paramagnetic resonance (EPR) can be used to study glassy and crystalline solid ethanol using two different nitroxide guest molecules incorporated in host ethanol matrix [3]. The switching of dynamical constraints in the nitroxide local environment was thermally controlled in the temperature range 5-80 K and probed by the effective spin-lattice relaxation and phase memory time measurements. Discussion of isotope substitution is provided with respect to methyl group dynamics and the physical processes relevant to spin relaxation proposed. References [1] Angell, C. A. 1995. Formation of glasses from liquids and biopolymers. Science 26:1924-1952. [2] Parak, F. 1993. Protein dynamics. 201: 332-345. [3] Kveder, M., D. Merunka, M. Jokić, B. Rakvin. 2008. Low-temperature electron-spin relaxation in the crystalline and glassy states of solid ethanol. Ph

Crystal-glass phase transition ; EPR

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