Why we need to look beyond the glass transition temperature to characterize the dynamics of thin supported polymer films.

ABSTRACT: There is significant variation in the reported magnitude and even the sign of [Formula: see text] shifts in thin polymer films with nominally the same chemistry, film thickness, and supporting substrate. The implicit assumption is that methods used to estimate [Formula: see text] in bulk materials are relevant for inferring dynamic changes in thin films. To test the validity of this assumption, we perform molecular simulations of a coarse-grained polymer melt supported on an attractive substrate. As observed in many experiments, we find that [Formula: see text] based on thermodynamic criteria (temperature dependence of film height or enthalpy) decreases with decreasing film thickness, regardless of the polymer-substrate interaction strength ε. In contrast, we find that [Formula: see text]

SUBMITTER: Zhang W 

PROVIDER: S-EPMC5984511 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature