Density-functional theory for polymer-carbon dioxide mixtures: A perturbed-chain SAFT approach

Abstract

We propose a density-functional theory (DFT) describing inhomogeneous polymer-carbon dioxide mixtures based on a perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS). The weight density functions from fundamental measure theory are used to extend the bulk excess Helmholtz free energy to the inhomogeneous case. The additional long-range dispersion contributions are included using a mean-field approach. We apply our DFT to the interfacial properties of polystyrene-CO 2 and poly(methyl methacrylate) CO 2 systems. Calculated values for both solubility and interfacial tension are in good agreement with experimental data. In comparison with our earlier DFT based on the Peng-Robinson-SAFT EOS, the current DFT produces quantitatively superior agreement with experimental data and is free of the unphysical behavior at high pressures (>35 MPa) in the earlier theory.

Bubble nucleation in polymer–CO2 mixtures

“…11 A simple explanation is that, at the same T and P 0 , the CO 2 solubility in the PS liquid is lower than in the PMMA liquid. 8 Moreover, at the same weight fraction of CO 2 , the spinodal value of PS-CO 2 is also lower than that of PMMA-CO 2 , which leads to a lower degree of supersaturation for the metastable uid at the ambient pressure. As the pressure is the controlling variable, we dene a relative degree of supersaturation S using the difference between the binodal pressure P b and the nucleation pressure P 1 , scaled by the difference between the binodal pressure and the spinodal pressure P s for a given weight fraction of CO 2 , i.e.…”

“…Details for the value of molecular weight (M), chain length of polymer or average size of the CO 2 cluster due to association interaction (N), energy parameter (3), monomer diameter (s) and k ij parameter for the species used in the model are given in our recent publication. 8 …”

Nonlocal Density Functional Theory and Grand Canonical Monte Carlo Molecular Simulations of Water Adsorption in Confined Media

“…Figure 3 represents the average adsorbed quantity per surface area N as a function of the reduced pressure P/P 0 . N is defined by (34) where N A is the Avogadro number. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 20 It is noticeable that in the narrowest pore (0.7 nm), the capillary condensation occurs remarkably soon (around P/P 0 = 0.1) and this may explain that no hysteresis appears when desorption is described.…”

Modeling of molecular gas adsorption isotherms on porous materials with hybrid PC-SAFT–DFT

“…As such DFTs also account for the excess free energies of chain connectivity and association, their application can be extended to a wide range of substances, [34][35][36][37][38] and it allows describing homogeneous and inhomogeneous properties in a consistent manner. Several of these DFTs have been applied for realistic fluid interface properties, among them, the models proposed by Xu et al [39], Hu et al [40], Llovell et al [41], Kahl et al [42], von Müller et al [43] and Klink et al [44] have been used to represent the interfacial properties of fluids such as hydrocarbons, CO 2 , H 2 O and polymers. However, the application of such molecular DFTs for realistic fluid confined in pores or near a solid surface is still limited.…”