Heuristic Guidelines for Developing Polymer/Ionic Liquid Blend Membranes

In the search of increasingly effective materials for enhancing gas transport in membranes, the incorporation of ionic liquids within a polymeric matrix is attracting a lot of interest in the development of advanced membranes to be applied to CO₂ separation. An analysis of the open literature focusing on polymer/IL blend membranes, in which a polymer matrix hosts an ionic liquid, was carried out, showing the effects of different composition dependences on CO₂ permeability. The peculiar permeability profiles were attributed to the specific interactions established between the ionic liquid and the polymer matrix rather than to the state of the polymer matrix. Hansen's solubility parameters were considered to represent CO₂ transport in polymer/IL blend membranes by linking them to interactions between the ionic liquid and the polymer matrix. Through an appropriate rearrangement of the solubility parameters, 2D maps were utilized as an immediate and easy tool to identify the best polymer/ionic liquid combination before even performing laboratory experiments.