New Challenges for the Pressure Evolution of the Glass Temperature

Abstract

The ways of portrayal of the pressure evolution of the glass temperature (T g ) beyond the dominated Simon-Glatzel-like pattern are discussed. This includes the possible common description of T g (P) dependences in systems described by dT g /dP > 0 and dT g /dP < 0. The latter can be associated with the maximum of T g (P) curve hidden in the negative pressures domain. The issue of volume and density changes along the vitrification curve is also discussed. Finally, the universal pattern of vitrification associated with the crossover from the low density (isotropic stretching) to the high density (isotropic compression) systems is proposed. Hypothetically, it may obey any glass former, from molecular liquids to colloids.

Correlation between glass transition temperature and the width of the glass transition interval

“…As far as we are aware so far no comprehensive experimental investigations have been performed in order to analyze the dependence of vitrification parameters on the rate of change of pressure. Such approach seems to us to represent a very useful alternative tool in varying the properties of glasses like the change of the glass transition temperature by pressure or pressure‐induced densification of glasses similar to vitrification in cooling…”

Pressure-Related Universal Previtreous Behavior of the Structural Relaxation Time and Apparent Fragility

“…The isothermal compressing constitutes the alternative path of approaching the glass transition. It offers unique possibilities of decoupling phenomena overlapping under atmospheric pressure, the selective focus on the free volume related properties or revealing the impact of phenomena "hidden" under pressure (Roland et al, 2005(Roland et al, , 2008Drozd-Rzoska et al, 2008a,b;Rzoska et al, 2010;Floudas et al, 2011;Kondrin et al, 2012;Rzoska, 2017).…”

“…where T = const, P < P g , and P g is for the glass (vitrification) pressure; V a (P) denotes the apparent activation volume (Roland et al, 2005(Roland et al, , 2008Rzoska et al, 2010;Floudas et al, 2011;Rzoska, 2017); τ ref . = τ P 0 is the reference prefactor.…”

“…The prefactor in SB Equation (2) can be approximated by the relaxation time under atmospheric pressure for the selected isotherm. Consequently, it ranges between 10 −10 s and 10s for the same glass former (Drozd- Rzoska et al, 2008a,b;Rzoska, 2017). The general SA-SB formula can be obtained linking Equations (1, 2) (Roland et al, 2005;Floudas et al, 2011):…”

“…In the last three decades Equation (8), due to its simplicity and the link to fragility via the fragility related coefficient D P , has become the key tool for describing τ (P) and η (P) experimental data in compressed glass-forming systems (Roland et al, 2005;Rzoska et al, 2010;Floudas et al, 2011;Rzoska, 2017;White and Lipson, 2018). Despite this success, there are still no theoretical models deriving Equation 8, often recalled as the pressure counterpart of the VFT relation: the PVFT equation (Roland et al, 2005;Floudas et al, 2011).…”