Predictions of Volume Relaxation in Glass Forming Materials Using a Stochastic Constitutive Model

Abstract

In a previous publication (Macromolecules 2012, 45, 7237), a stochastic model of the glassy state that acknowledges dynamic heterogeneity was shown to describe the classic Kovacs poly(vinyl acetate) volume relaxation data set with the exception of the expansion gap and the pressure dependence of the glass transition temperature. This initial model included two assumptions–the relaxation time of the meso-domain was controlled by the specific volume and the fluctuations were isotropic. Recently, a fully tensorial stochastic constitutive model (SCM) was developed where (i) the relaxation time was a function of both the configurational entropy and the stress tensor and (ii) nonisotropic fluctuations were allowed. In the present work, the SCM is shown to predict the Kovacs data, including the expansion gap as well as the pressure dependence of the glass transition temperature.