Nonequilibrium Lattice Fluid Modeling of Gas Solubility in HAB-6FDA Polyimide and Its Thermally Rearranged Analogues

Abstract

For the first time, a theoretical analysis of gas sorption, based on the non-equilibrium lattice fluid (NELF) model, in chemically-imidized HAB-6FDA polyimide and its thermally rearranged analogs is presented. Due to the inaccessibility of pVT data in the rubbery region, the characteristic lattice fluid parameters of the polymers considered in this study were obtained from a collection of infinite dilution solubility data at multiple temperatures. Hydrogen, nitrogen and methane sorption isotherms at 35°C were fit to the NELF model using one adjustable parameter, i.e., the polymer-penetrant binary interaction parameter, 12 k . The optimal value of 12 k for each polymer-penetrant pair was used to predict hydrogen, nitrogen and methane sorption isotherms at other temperatures and at pressures up to 6 MPa. For carbon dioxide, a second adjustable parameter, the swelling coefficient, was introduced to account for sorption-induced matrix dilation. The ideal solubility-selectivity is also predicted for several gas pairs. The increase in gas sorption in thermally rearranged samples relative to their polyimide precursor is essentially due to entropic effects, i.e., to the increase in non-equilibrium fractional free volume during thermal rearrangement.

Influence of temperature on gas solubility in thermally rearranged (TR) polymers

“…Finally, polymer-penetrant interactions could also influence enthalpies of sorption. However, a theoretical analysis of gas sorption in HAB-6FDA and its TR analogues was recently reported [36]. The polymer-penetrant binary interaction parameters calculated in the study by Galizia et al were not large, which indicates that polymer-penetrant interactions are minimal.…”

Effect of relative humidity on the gas transport properties of zeolite A/PTMSP mixed matrix membranes

“…† For all gases, k ij is slightly positive, in agreement with the values reported for other glassy polymers as PIM-1 47 and HAB-6FDA polyimides. 48 For water vapour sorption, the binary parameters reported in Table 2 were adjusted using the isotherm reported by Scholes et al 21 …”

“…† For all gases, k ij is slightly positive, in agreement with the values reported for other glassy polymers as PIM-1 47 and HAB-6FDA polyimides. 48 For water vapour sorption, the binary parameters reported in Table 2 were adjusted using the isotherm reported by Scholes et al 21 In addition, the model has been modied to take into account the gas sorption into MMMs. 46,49 The mass of penetrant adsorbed in the MMM per unit mass of total solid, U M , is evaluated from the mass adsorbed on the pure ller per unit mass of ller, U F , and that adsorbed in the polymeric phase of the MMM per unit mass of polymer, U P,MM :…”

Non-equilibrium Lattice Fluid Modeling of Gas Sorption for Fluorinated Poly(ether imide)s

“…Additionally, the k 12 parameter describes the deviation from the geometric mixing rule as dictated by Hildebrand's solution theory, where a value of zero represents ideal interactions, positive values represent unfavorable (i.e., less than ideal) interactions, and negative values represent favorable (i.e., greater than ideal) interactions. 20 This parameter, present in eq 4, is dependent only on the gas− polymer pair and is treated as an adjustable, best-fit parameter between the model and data of a reference sorption isotherm. Assuming no penetrant-induced swelling, once the k 12 parameter is determined for the gas−polymer pair, the value can be reused to obtain isotherms for all other temperatures in a fully predictive manner.…”