Activation induced fluidization of a confined viscous liquid

Abstract

Confinement of supercooled liquids into nano-pores induces a strong modification of the dynamics. In this work we raise the issue as how this confinement effect is modified when the liquid is out of equilibrium. To answer that question, we use molecular dynamics simulations to investigate the effect of confinement on a supercooled liquid activated by the periodic folding of a molecular motor. The excitation (i.e. elementary diffusion processes) density calculation shows that the motor’s opening angle controls the activation of the medium. We then use that result to study the effect of different activations on the confined supercooled liquid. When our liquid is not activated, the confinement generates a strong slowing down of the dynamics, and the excitation density decreases sharply around the pore wall. In contrast when the liquid is activated the motor generates excitations inside the medium localized mostly in the pore center. The combination of these two effects leads to a localization of the excitation density when the motor is on. Results show that the activation is able to wash out the confinement-induced slowing down while the main characteristics of supercooled liquids are maintained or increased. We observe actually an increase of the tail of the Van Hove correlation function upon activation inside the pores leading to the increase of the Non Gaussian parameter, two signatures of dynamic heterogeneity in supercooled liquids.