Aging of polymers of intrinsic microporosity tracked by methanol vapour permeation

Abstract

The initially very promising transport properties of glassy high free volume polymers deteriorate rapidly over time. In this work, we focused on this aging phenomenon in two polymers of intrinsic microporosity (PIMs), namely PIM-1 and PIM-EA-TB. To identify the main mechanisms involved, we studied the time-declines of permeability and diffusivity of methanol vapours in flat membranes with approximately equal thicknesses. The permeation measurements were carried out using a continuous flow permeation method with carrier gas, where the methanol vapours were held at constant activity 0.2 at 25°C. Two different experimental modes were used: (i) continuous experiments that consisted of one long experiment with a duration of over 650 hours for each polymer and (ii) momentary experiments that consisted of a vast number of short (ca. 6 hours) consecutive measurements of transient permeation. The observed decreases of methanol permeability due to aging were more intense in the case of continuous mode for both polymers. In other words, the aging was ca.

Assessment of the long-term stability of the polymer of intrinsic microporosity PIM-1 for hydrogen storage applications

“…[34] Glassy polymers such as PIM-1 are intrinsically non-equilibrium materials and are known to lose free volume over time, owing to slow rearrangements in the packing of the polymer chains. This physical aging [35] was found to be the primary cause of the well-established decay in permeability of PIM-1 membranes over time. [36] Interestingly, aging of the polymer was found to impact not only its permeability, but also to enhance its selectivity, [37] which is a critical parameter when evaluating the performance of polymer-based membranes.…”

Gas Permeation Properties, Physical Aging, and Its Mitigation in High Free Volume Glassy Polymers

“…26 It was also previously discovered that aging rate correlates strongly to the T g of the polymer 27 and that T g increases with physical aging. 28 Although physical aging occurs without any external influence, its rate is found to be dependent on several factors, such as temperature, [29][30][31][32] gas environment, [33][34][35] and polymer structure. 33,36 More importantly, it was observed that physical aging occurs more rapidly in a thin polymer film (i.e.…”

The synthesis, chain-packing simulation and long-term gas permeability of highly selective spirobifluorene-based polymers of intrinsic microporosity

“…Methanol treatment has been shown previously to reverse the effects of physical ageing for glassy ultra-permeable polymers and it also removes the last residues of casting solvent. 16,39,40 In addition, methanol treatment allows a direct comparison between the gas permeabilities of different polymers prior to ageing. The equivalent data for a freshly methanol treated lm of PIM-1 of similar thickness, measured under identical conditions to those of the PIM-SBFs, are also provided in Table 2 /CH 4 gas pairs and can be directly ascribed to the greater rigidity of the SBF units as compared to SBI units of PIM-1.…”