Coupling between Molecular Mobility and Kinetics of Crystal Growth in a Hydrogen-Bonded Liquid.

Our aim here is to gain new insight into the nature of the crystalline phase formed in supercooled glycerol near the glass transition temperature and to establish the interrelationship between the kinetics of crystal growth and fundamental dynamic properties. The liquid's dynamics and the crystalline development in glycerol, a hydrogen-bonded liquid, is studied by means of dielectric spectroscopy. We monitored the kinetics of crystallization by isothermal treatment at temperatures between 220 and 240 K (T g = 185 K). Given the thermal protocol employed, we stimulated the growth of the crystalline phase from pre-existing nuclei, in such a way that the observed kinetics is dominated by the crystal growth step. Our experimental results are discussed in terms of the classical theory of crystallization which predicts a significant correlation between the liquid's diffusion and the crystal growth rate. The coupling between dynamic properties, such as dielectric α relaxation time, viscosity, and self-diffusion coefficient, and the characteristic crystal growth time is analyzed. We find that the crystal growth time scales with the glycerol's self-diffusion coefficient as τcryst ∝ D -0.85, confirming that the liquid's dynamics is the principal factor governing the crystal growth in glycerol above but close T g. [ABSTRACT FROM AUTHOR]