Self-Confined Dynamics in supercooled Isopropanol during crystallization as revealed by quasielastic neutron scattering methods

Abstract

Over the last decades, hydrogen bonding systems have attracted the interest of the scientific community for its strong implications in a wide a range of molecular properties. Low molecular weight monohydroxy alcohols are excellent glass formers and their structural and dynamic properties have been extensively discussed at the crystalline, glassy, supercooled liquid and ordinary liquid states [1-3]. Isopropyl alcohol (isopropanol can easily form a glass if cooled fast enough to avoid the crystallization process. The structure, dynamics and the thermodynamic properties of isopropanol have been widely studied and frequently discussed in terms of the molecular aggregates formed by the hydrogen bonds [3]. We have studied the dynamics of isopropanol during crystallization by using quasielastic neutron scattering methods in real time. In this case, supercooled liquid isopropanol has been subjected to isothermal annealing above its glass transition temperature. Our results reveal that the time scale of the isopropanol reorientation dynamics is altered for the late stages of the crystallization process. We propose the existence of a confinement effect during the transformation of amorphous isopropanol into its triclinic phase, in this way modifying the intrinsic nature of the dynamics assessed by quasielastic neutron scattering at the ns timescale, mainly for low values of the momentum transfer.