Negative Pressure Vitrification of the Isochorically Confined Liquid in Nanopores

Abstract

Dielectric relaxation studies for model glass-forming liquids confined to nanoporous alumina matrices were examined together with high-pressure results. For confined liquids which show the deviation from bulk dynamics upon approaching the glass transition (the change from the Vogel-Fulcher-Tammann to the Arrhenius law), we have observed a striking agreement between the temperature dependence of the α-relaxation time in the Arrhenius-like region and the isochoric relaxation times extrapolated from the positive range of pressure to the negative pressure domain. Our finding provides strong evidence that glass-forming liquid confined to native nanopores enters the isochoric conditions once the mobility of the interfacial layer becomes frozen in. This results in the negative pressure effects on cooling. We also demonstrate that differences in the sensitivity of various glass-forming liquids to the "confinement effects" can be rationalized by considering the relative importance of thermal energy and density contributions in controlling the α-relaxation dynamics (the E(v)/E(p) ratio).

On the Segmental Dynamics and the Glass Transition Behavior of Poly(2-vinylpyridine) in One- and Two-Dimensional Nanometric Confinement

“… 45 Likewise, the much different behavior of low-molecular-weight liquids glycerol (35 K/GPa) and salol (204 K/GPa) confined in alumina templates was explained in terms of the different contribution of volume and thermal effects in controlling their glassy dynamics. 33 In line with this, the relatively weak sensitivity of P2VP to pressure/density effects might be the origin of its bulk-like behavior in AAO nanopores. One can also use the same type of argumentation for 1,4- cis -polyisoprene ( dT g / dP = 178 K/GPa), 95 in which glass transition temperature was unaffected by 2D confinement, whereas, at the same time, a remarkable broadening of the distribution of relaxation times for both the segmental and chain modes was observed.…”

Testing density scaling in nanopore-confinement for hydrogen-bonded liquid dipropylene glycol

“…It is well-established that the dynamics of the liquids conned to nanometer pores is much different from that in the bulk state. [29][30][31][32][33][34][35] In the presence of nanoscale connement, it has been observed that on cooling the temperature dependence of the structural relaxation time starts to depart from the bulk-behavior. This happens as due to verication of the interfacial layer, that is the fraction of molecules located in close proximity of the pore walls.…”

“…Surprisingly, to do that we use the same value of the scaling exponent g as that found for substances measured in the bulk. [29][30][31] What remains unclear, however, is whether the idea of the density scaling works in conned geometry for these glass-forming systems which for sure, does not scale in bulk supercooled liquid state.…”

Distributions of pore sizes and atomic densities in binary mixtures revealed by molecular dynamics simulations

“…To date, several experimental studies have been performed to understand the constant volume vitrification [32][33][34][35][36][37][38][39]. The works include experimental studies of glass transition taking place in confined environments.…”