Communication: Crystallite nucleation in supercooled glycerol near the glass transition

Abstract

Heterogeneity and solid-like structures found near the glass transition provide a key to a better understanding of supercooled liquids and of the glass transition. However, the formation of solid-like structures and its effect on spatial heterogeneity in supercooled liquids is neither well documented nor well understood. In this work, we reveal the crystalline nature of the solid-like structures in supercooled glycerol by means of neutron scattering. The results indicate that inhomogeneous nucleation happens at temperatures near T g . Nevertheless, the thermal history of the sample is essential for crystallization. This implies such structures in supercooled liquids strongly depend on thermal history. Our work suggests that different thermal histories may lead to different structures and therefore to different length and time scales of heterogeneity near the glass transition.

Liquid dynamics in partially crystalline glycerol

“…The solidification was induced by a two-step annealing procedure as suggested before 24,25 . Our dielectric data reveal that liquid glycerol, through a nucleation step at 190 K and subsequent crystal growth at 230 K, transforms into a new phase.…”

“…Even so, one can find in the literature several works mainly focused on the high frequency dynamics of the crystalline state [21][22][23] . Nevertheless, real time investigations of its transformation into solid-like structures have recently attracted the interest of some authors 24,25 . Inspired by previous works on the existence of long-lived dynamic heterogeneities in supercooled glycerol, Möbious et al performed real time aging experiments above T g and detected the formation of a solid phase that showed a distinct mechanical response as compared to the orthorhombic crystal 24 .…”

“…In this way, Möbious and co-authors speculated on the existence of a glacial phase 26 , that is, either a second amorphous state or a frustrated crystal with a high degree of defects and disorder. Two years later, by employing time-resolved neutron scattering, Yuan and co-authors aimed to unravel the structural nature of this solid-like phase 25 . They revealed, in agreement with one of the interpretations given by Möbious et al, the formation of a crystalline lattice.…”

A systematic study of the isothermal crystallization of the mono-alcohol n-butanol monitored by dielectric spectroscopy

“…Some liquids, like water, crystallize readily at moderate supercooling and need fast quenching below the melting temperature in order to avoid crystallization. Others, like the prototype glass-former glycerol, supercool easily and require a careful protocol to crystallize [5]. But the true thermodynamic equilibrium state for all supercooled liquids and glasses is unarguably the crystal, and thus crystallization is their eventual inevitable fate.…”

“…But understanding the crystallization process is also interesting from a fundamental point of view. Crystallization studies are however difficult to carry out in a controlled and reproducible manner, because many factors influence the initiation and course of crystallization, such as sample preparation, thermal history, presence of impurities, container geometry, etc [5][6][7].…”