Combined Description of Polymer PVT and Relaxation Data using a Dynamic "SL-TS2" Mean-Field Lattice Model

We develop a combined model to describe the pressure-volume-temperature (PVT) thermodynamics and the α- and β-relaxation time dynamics in glass-forming amorphous materials. The PVT results are described using a two-state modification of the Sanchez-Lacombe equation of state (SL-EoS), while the dielectric relaxation is captured using the TS2 mean-field model (Soft Matter 16, 810 [2020]). The application of simple first-order kinetic equations also allows us to study the volume recovery after so-called “down jumps” (when the material is rapidly cooled from liquid to glassy state). We applied the new framework to describe experimental data for polystyrene and poly(methylmethacrylate) and found a good qualitative and quantitative agreement.