The properties of a molecular liquid confined at the nanometer length scale can be very distinct from the bulk. For that reason, the macro- and the nanoscopic behaviors of glass-forming liquids are regarded as two nonconnected realms, governed by their own rules. Here, we show that the glassy dynamics in molecular liquids confined to nanometer pores might obey the density scaling relation, ρ/T, just like in bulk fluids. Even more surprisingly, the same value of the scaling exponent γ superposes the α-relaxation time measured at different state points in nanoscale confinement and upon increased pressure. We report this remarkable finding for van der Waals liquids tetramethyl-tetraphenyl-trisiloxane (DC704) and polyphenyl ether (5PPE), considered as simple, single-parameter liquids. Demonstrating that the density scaling idea can be fulfilled in both environments opens an exciting possibility to predict the dynamic features of the nanoconfined system close to its glass-transition temperature from the high-pressure studies of the bulk liquid. Likewise, we can describe the viscous liquid dynamics at any given combination of temperature and pressure based on analysis of its behavior in nanopores.

Here, we have studied the effect of spatial restrictions on the molecular dynamics and crystallization behavior of modeled lipophilic drug fenofibrate incorporated into nanoporous aluminum oxide membranes of different pore size. Our measurements demonstrate that, on subsequent cooling, dynamics of confined liquid split up into two distinct fractions, due to the presence of core and interfacial layers. At the temperature, at which vitrification of the interfacial layer takes place (T g_interface), departure from the bulk-like behavior occurs, and molecules in the center of the pores enter quasi-isochoric conditions. Depending on the thermal protocol and pore size, the volume fixed at T g_interface might be a bit different so as the core liquid’s dynamics. Interestingly, below that temperature, the nanoconfined liquid can still obey the fundamental density scaling relation (1/TV γ), just like in the bulk phase, while not necessarily isochronal superposition. This is in contrast to a common observation that the validity of the density scaling in bulk glass-forming systems always goes together with isochronal superposition of the α-relaxation, and vice versa. Finally, our careful analysis of the crystallization kinetics as a function of lowering pore diameter indicates for systematic slowing down crystallization progress, the shift of the maximum crystallization rate toward higher undercooling and decrease in the dimensionality of growing crystals.

In this work, we have performed a detailed investigation on the crystallization tendency of the modeled glass-forming pharmaceutical compound, fenofibrate. To do this, we have employed four different experimental techniques allowing following of the crystallization process. This has included dielectric spectroscopy, optical microscopy, X-ray diffraction and differential scanning calorimetry. From the crystallization kinetic studies carried out at atmospheric pressure, we have determined the temperature dependence of the crystal growth rate and the overall crystallization rate. It was found that the time scale of the molecular motions responsible for α-relaxation correlates much better with the crystal growth rate than with the overall crystallization rate. Experiments carried out under varying thermodynamic conditions while remaining on the same timescale of α-relaxation have demonstrated that the crystallization tendency of the supercooled fenofibrate significantly slows down with increasing pressure. Lastly, we have also shown that the thermodynamic history of reaching crystallization conditions has a substantial impact on its overall progress.