Reaching the ideal glass transition by aging polymer films

TL;DR

This study demonstrates that ultrathin polystyrene films can reach thermodynamic states near the Kauzmann temperature through aging, providing evidence for the ideal glass transition by observing enthalpy recovery and stabilization.

Contribution

It shows that aging in thin polymer films can access states close to the ideal glass transition, revealing new insights into glass thermodynamics.

Findings

Enthalpy recovery allows reaching the Kauzmann temperature.

No further enthalpy decrease observed after reaching $T_K$.

Evidence supports the existence of the ideal glass transition.

Abstract

Searching for the ideal glass transition, we exploit the ability of glassy polymer films to explore low energy states in remarkably short time scales. We use 30 nm thick polystyrene (PS) films, which in the supercooled state basically display the bulk polymer equilibrium thermodynamics and dynamics. We show that in the glassy state, this system exhibits two mechanisms of equilibrium recovery. The faster one, active well below the kinetic glass transition temperature ($T_g$), allows massive enthalpy recovery. This implies that the 'fictive' temperature ($T_f$) reaches values as low as the predicted Kauzmann temperature ($T_K$) for PS. Once the thermodynamic state corresponding to $T_f = T_K$ is reached, no further decrease of enthalpy is observed. This is interpreted as a signature of the ideal glass transition.