Calorimetric and acoustic experiments on orientationally disordered and fully ordered crystalline phases of ethanol

• Published in: Journal of physics. Condensed matter Vol. 19; no. 20; pp. 205135 - 205135 (10)
• Main Authors: Ramos, M A, Rodríguez-Mora, V, Jiménez-Riobóo, R J
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 23.05.2007; Institute of Physics
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General studies of phase transitions; Glass transitions; Order-disorder and statistical mechanics of model systems; Physics; Specific phase transitions; Structure of solids and liquids; crystallography; Crystalline phase; Order-disorder transformations; Ethanol; Glass; Melting points; Monoclinic lattices; Glass transition; Specific heat; Plastic crystals; Supercooled liquids; Orientation disorder; BCC lattices; Brillouin spectra; Calorimetry; Kinetics; Thermodynamic properties; Polymorphism
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/19/20/205135

Ethanol exhibits a very interesting polymorphism, presenting different solid phases below its melting point at 159 K: a structural (amorphous) glass, by quenching the supercooled liquid below the glass-transition temperature Tg = 97 K; a (bcc) plastic crystal, which by quenching below the same Tg = 97 K becomes an orientationally disordered crystal with glassy properties (sometimes named a 'glassy crystal'); and fully ordered (monoclinic) crystals. We present here new calorimetric experiments and specific-heat measurements of the different phases of ethanol in the relevant temperature range around the glass-transition and melting temperatures. In addition, we have concurrently performed Brillouin-scattering experiments on these crystalline phases, both fully ordered and orientationally disordered ones, that complement our earlier studies of the glass phases. The possible role of water impurities in kinetic and thermodynamic properties has also been investigated.