Mixed equilibrium/nonequilibrium effects govern surface mobility in polymer glasses

2024/02/10 by Jianquan Xu, Asieh Ghanekarade, Xu, Jianquan +14
Chemistry · Materials Science · #Adsorption, diffusion, and thermodynamic properties of materials #FOS: Physical sciences #Material Dynamics and Properties #Materials Science (cond-mat.mtrl-sci) #Soft Condensed Matter (cond-mat.soft)

paper · pdf · doi:10.48550/arxiv.2402.06917

openalex publication_date 2024/02/10 · openalex created_date 2024/02/14 · openalex updated_date 2026/07/28

Abstract

The temperature at which supercooled liquids turn into solid-like glasses (T_g) can change at the free surface, affecting the properties of nanostructured glasses and their applications. However, inadequate experimental resolution to determine the T_g gradient and a longstanding debate over the role of nonequilibrium effects have hindered fundamental understanding of this phenomenon. Using spatially resolved T_g measurements and molecular dynamics simulations, we reveal a crossover from equilibrium behavior to a new regime of near-surface nonequilibrium glass physics on cooling. This crossover causes the form of the nonequilibrium T_g gradient to change, highlighting the need to include these physics for rational understanding of the properties of realistic nanostructured glass-forming materials. They also potentially recast the interpretation of decades of experimental data on nanoconfined glasses.

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