Physical Aging of Polymers

Abstract

Abstract This article provides an overview of the most important aspects of physical aging of polymers. First, we briefly introduce basic concepts of the glass transition, that is, the way a nonequilibrium glass is formed. Subsequently, after presenting the way physical aging can be monitored, we describe the main well‐established signatures of physical aging, that is, its nonexponential and nonlinear nature. The next part of the article is dedicated to recent advancements in the physical aging of bulk polymers. In this context, recent experimental activity is discussed, where the existence of multiple mechanisms for equilibrium recovery is presented. In addition, important aspects of physical aging in polymers altered by geometrical confinement are scrutinized in light of the past 20 years efforts aiming to understand glass dynamics in such conditions. It is shown how confined polymers weakly interacting with the confining medium exhibit accelerated physical aging. Importantly, such acceleration was found to be decoupled from the molecular mobility of the glass. Finally, we briefly discuss how recent advancements in physical aging of polymers in bulk and under geometrical confinement should foster experimental efforts to unveil important basic aspects of the glass transition, such as the existence of the so‐called “ideal glass.”