Phenomenology of vapour sorption in polymers of intrinsic microporosity PIM-1 and PIM-EA-TB: envelopment of sorption isotherms

Vapour sorption isotherms for PIM-1 and PIM-EA-TB exhibit specific sigmoidal shapes. Moreover, obtained sorption uptakes of tested organic compounds appear inside confined envelopes while the volatility of the sorptive strongly influences the sorption uptakes. Thus, the infinite dilution solubility coefficients depend mainly on the vapour pressure of the sorptive. Sorption isotherms were parameterised with the GAB model of multilayer adsorption. Although the observed sorption isotherms likely result from a rather complex phenomenon involving adsorption, micropore filling and plasticization of the polymer, the model provided physically interpretable parameter values. In particular, one adsorption centre (as assumed by the GAB model) is formed by-0.7 mer units of either PIM-1 or PIM-EA-TB for all sorptives. We hypothesize that sorption isotherms of other than tested volatile compounds in PIM-1 and PIM-EA-TB can presumably fit into the observed sorption envelopes and that other PIMs should exhibit similar sorption envelopments.

Automated summary

Vapour sorption isotherms for PIM-1 and PIM-EA-TB show specific sigmoidal shapes and are strongly influenced by the volatility of the sorptive. The GAB model is used to parameterize the sorption isotherms, providing physically interpretable parameter values.