Toward Better Understanding Crystallization of Supercooled Liquids under Compression: Isochronal Crystallization Kinetics Approach

In this paper, we present dielectric studies on the effect of different thermodynamic conditions on the physical stability of van der Waals glass-forming material of pharmaceutical interest, indomethacin. By maintaining isochronal condition during measurements, we were able to control the kinetic factor of the crystallization process and untangle purely thermodynamic effects on crystallization from kinetic ones. This cannot be achieved by any other experimental attempt performed at atmospheric pressure. Along with experimental studies, crystallization of supercooled indomethacin under pressure was described theoretically. We have demonstrated within the studied pressure range (0.1-220 MPa) that one should expect an increase of thermodynamic driving force, decrease in melt/crystal interface energy, and critical nuclei size. Therefore, an experimentally observed increase in the overall crystallization rate under isochronal conditions can be exclusively rationalized as due to variations of the thermodynamic factor.