(376e) Fundamental Pure and Mixed Liquid Sorption Properties of Osn Membranes Based on Polybenzimidazoles
In this study, free standing, mechanically robust flat membranes based on Celazole® were cast from DMAc2. Pure and mixed solvent and solute sorption experiments were carried out at room temperature. Among solvents, hydrocarbons, alcohols, acetone, toluene, ethyl acetate and water were considered. N-decane and PEG400 were used as mimic standard solutes. Interestingly, molar solubility decreases by an order of magnitude with increasing penetrant molar volume, which points out that liquids sorption in Celazole® is controlled essentially by entropic factors. Indeed, as long as penetrant size increases, it is less likely to accommodate penetrant molecules into the polymer matrix3. However, this rapid decrease is followed by a plateau, where sorption changes little with penetrant chemical nature and size.
When considering sorption of isomers, solubility starts to be affected by enthalpic effects. Specifically, 1-propanol solubility is 5 times higher than 2-propanol solubility. Such behavior can be justified by considering that, while 1-propanol can easily form hydrogen bonds with the amine groups on the polymer backbone, 2-propanol is less prone to do so, since the âOH group is much more sterically screened.
Finally, the effect of the second component on solvent and solute solubility in CelazoleÂ® was also investigated using model mixtures, such as methanol-PEG400.
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