Mixed-Penetrant Sorption in Ultrathin Films of Polymer of Intrinsic Microporosity PIM-1

Abstract

Mixed-penetrant sorption into ultrathin films of a superglassy polymer of intrinsic microporosity (PIM-1) was studied for the first time by using interference-enhanced in situ spectroscopic ellipsometry. PIM-1 swelling and the concurrent changes in its refractive index were determined in ultrathin (12-14 nm) films exposed to pure and mixed penetrants. The penetrants included water, n-hexane, and ethanol and were chosen on the basis of their significantly different penetrant-penetrant and penetrant-polymer affinities. This allowed studying microporous polymer responses at diverse ternary compositions and revealed effects such as competition for the sorption sites (for water/n-hexane or ethanol/n-hexane) or enhancement in sorption of typically weakly sorbing water in the presence of more highly sorbing ethanol. The results reveal details of the mutual sorption effects which often complicate comprehension of glassy polymers' behavior in applications such as high-performance membranes, adsorbents, or catalysts. Mixed-penetrant effects are typically very challenging to study directly, and their understanding is necessary owing to a broadly recognized inadequacy of simple extrapolations from measurements in a pure component environment.

CO2/CH4 Pure- and Mixed-Gas Dilation and Sorption in Thin (∼500 nm) and Ultrathin (∼50 nm) Polymers of Intrinsic Microporosity

“…The refractive index change data of Figure 3b clearly indicate that the "Thick" PTMSP indeed accommodated pure CO 2 and CH 4 , mostly within its extremely large EFFV. The refractive index change reached an extraordinarily high value of 2.5% (the highest reported among similar studies 21,22,24 ). At the same time, the PTMSP matrix did not dilate nearly as much as PIM-1 (Figure 3a), and the resulting penetrant concentration was slightly lower in "Thick" PTMSP than in "Thick" PIM-1.…”

“…In this part, we compare the refractive index changes and dilation recorded during pure and mixed CO 2 and CH 4 gas sorption experiments in “Thick” and “Thin” films of CTA, PIM-1, and PTMSP. Unfortunately, individual penetrant uptakes for mixed-gas experiments could not be calculated because of the fundamental limitations of the employed technique Figure shows mixed-gas refractive index changes of “Thick” and “Thin” films of CTA, PIM-1, and PTMSP exposed to 50:50 CO 2 –CH 4 molar mixtures.…”

“…To aid the development of thin-film membrane systems, it is vital to study the sorption, diffusion, and permeation behavior of thin (<1 μm) films under high-pressure pure- − and multicomponent penetrants. For example, Tiwari et al have recently investigated CO 2 sorption in ∼125 nm PIM-1 films using in situ spectroscopic ellipsometry and detected reductions in gas solubility with aging.…”

Nano-Confinement Effects on Structural Development and Organic Solvent-Induced Swelling of Ultrathin Carbon Molecular Sieve Films

“…The presence of the ∼500 nm thick silicon oxide underneath each polymer/carbon film amplified the accuracy of the analysis versus the more broadly used native oxide wafers, as thoroughly investigated before. 15 , 32 , 33 An example of the optical model is presented in the Supporting Information (Figure S2). Error bars were estimated based on the fit parameter uniqueness analysis assuming as threshold a 25% reduction of the mean squared error (MSE).…”

High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement

“…33 The chemical structures and some relevant properties of the polymers are listed in Table 1. [34][35][36] , the rejuvenation procedure helped to re-set the thermal history and produce films with well-defined and reproducible starting properties. Even though the rejuvenation procedure was not necessary for PS, as its Tg = 100 °C is easily accessible, it was still performed to assure comparability of the results.…”