Vapor−Liquid Equilibrium of Polymer + Solvent Mixtures by the Chain-of-Rotators Equation of State

Abstract

Vapor−liquid equilibrium (VLE) of polymer + solvent mixtures is described by the chain-of-rotators (COR) equation of state (EOS) using segment parameters that are applicable to polymers of varying molecular weight. Segment parameters a and b are obtained from small molecules of the same chemical structure as the polymer segment. The segment parameter c is then obtained by fitting polymer pressure−volume−temperature (PVT) data. van der Waals and free energy matching mixing rules are investigated to describe mixtures of various types. Excellent correlation of VLE data is obtained for all mixtures studied by using only one constant interaction coefficient for a, k 12, in the van der Waals mixing rule independent of temperature or polymer molecular weight. VLE predictions from the COR EOS by using van der Waals mixing rules with zero k 12 as well as by using UNIFAC free energy matched mixing rules are presented. For the majority of systems studied, both predictive methods gave better or equal results compared to the UNIFAC−FV model (FV = free volume).

Polystyrene freeze-dried from dilute solution: Tg depression and residual solvent effects

“…[6,[9][10][11]15] It is not at all clear why it becomes more difficult to remove residual solvent from materials freeze-dried from more dilute solutions. The benzene vapor pressure of 0.1 wt% benzene in polystyrene is 0.26 Torr at 15 8C, based on the chain-of-rotators equation of state [43,44], indicating that nearly complete removal of the solvent should be achievable at room temperature under moderate vacuum in contrast to our experimental results (as shown, for example, in Fig. 7).…”

Vapor−Liquid Equilibrium for Polymer−Diluent Systems from Melting Point Depression

“…Additionally, for melt polycondensation processes, VLE data for polymer−diluent systems is critical for design of finishers and extruders, where trace levels of condensation products (or solvent) are devolatilized from highly viscous polymer melts. Though such data are reported for a few systems in the literature, − it is not available for the systems of interest, namely polybutylene terephthalate (PBT) in the presence of 1,4-butanediol (BDO) and tetrahydrofuran (THF).…”