Reorientation dynamics in thin glassy films

TL;DR

This study investigates how the orientational relaxation dynamics in thin glassy films vary with temperature and thickness, revealing that confinement influences relaxation time distribution near the glass transition but not in the deep glassy state.

Contribution

It provides new insights into the effects of confinement on glassy dynamics by measuring relaxation time distributions across different temperatures and film thicknesses.

Findings

Distribution width increases under confinement near the glass transition

Confinement effects diminish in the deep glassy state

Relaxation dynamics are probed using second-harmonic generation

Abstract

We present a study of orientational relaxation dynamics in thin films of a low-molecular-weight glass-former as a function of temperature and film thickness. The relaxation is probed by second-harmonic generation after release of a poling electric field. From the measured decays of the second-harmonic signal and their fitting with a stretched exponential, we can determine the distribution of relaxation times in the system. As temperature decreases from above the glass transition, we observe that the width of the distribution first increases under confinement, but that deeper in the glassy state, confinement has no effect anymore on the dynamics.