Cooling-Rate versus Compression-Rate Dependence of the Crystallization in the Glass-Forming Liquid, Propylene Carbonate

The effect of cooling and compression rates on the tendency to crystallize/vitrify the canonical glass-forming liquid, propylene carbonate (PC), was studied by using dielectric spectroscopy. Based on constructed time-temperature transformation (TTT) and continuous heating transformation (CHT) diagrams, we have determined the critical scanning rates that allow avoiding crystallization on cooling from the liquid state and reheating of the glassy sample, respectively. In a similar way to isobaric temperature dependent studies, we have also carried out isothermal high-pressure measurements upon which the crystallization tendency of PC was examined as a function of varying compression and decompression rates (pressures up to 1.3 GPa). We propose time pressure transformation (TPT) and continuous decompression transformation (CDT) diagrams as the pressure analogs of the TTT and CHT diagrams. Obtained results demonstrate that, qualitatively, one gets the same picture when pressure (instead of the temperature) is used as the principal adjustable thermodynamic parameter. In agreement with this finding, a careful comparison of the time-dependent crystallization results collected under isobaric and isothermal conditions has revealed that within the considered T-p range the maximal crystallization rate and dimensionality of the growing crystals do not depend significantly on whether we vary with the temperature at a fixed pressure or pressure at a constant temperature.