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

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