(730b) Influence of Molecular Interactions, Membrane Swelling and Plasticization on Pure and Mixed Fluid Transport in OSN Membranes
In this study, the solubility of several pure and mixed organic species in Celazole®, a commercial polybenzimidazole, has been investigated. Polymer volumetric dilation upon liquid sorption has been investigated as well, using the optical method. The role of polymer-penetrant interactions, membrane degree of swelling, and penetrant clustering on small molecule sorption and transport in Celazole® has been discussed and several structure-property correlations were identified. Methanol was selected as a model penetrant to run sorption and diffusion experiments in the activity range 0-1. Methanol and other polar lower alcohols cause severe matrix plasticization. We have hypothesized the possible mechanism of Celazole® plasticization. Specifically, methanol (as well as other polar penetrants) likely break the inter-chain hydrogen bonds in favor of polymer-penetrant hydrogen bonds, according to a mechanism that we could define as competitive hydrogen bonding. The breaking of the original polymeric network would increase, in turn, the distance between polymer chains, thus enhancing their mobility. This picture helps to rationalize mixed methanol-PEG400 sorption data. In contrast, Celazole® is very stable in non-polar aliphatic and aromatic hydrocarbons.
Finally, the polymer mechanical properties were measured before and after soaking in liquid water and methanol. The results provide further proof that polar liquids severely plasticize Celazole®.