Theoretically Self-Consistent Nonequilibrium Thermodynamics of Glassy Polymer Theory for the Solubility of Vapors and Liquids in Glassy Polymers

The nonequilibrium thermodynamics of glassy polymer (NETGP) theory provides a formalism to calculate solubilities of volatile species in glassy polymers using equilibrium free energies. The classic NETGP approach of Sarti and Doghieri assumes that the glassy polymer density of a solvent swollen polymer is known a priori. In the modified approach developed in this work, this density is calculated self-consistently. The self-consistent calculation of the swollen polymer density has profound implications on both the theoretical and practical aspects of the theory. This is accomplished by means of a new class of perturbation theory, which assumes that the sorption of volatile species in a glassy polymer can be treated as a perturbation to a dry polymer reference state. The new approach is then validated against sorption data in several glassy polymers.