Optimisation of transport properties of polyurethane-based pervaporation membranes by a polymer molecular structure design

This article discusses the relationship between a molecular structure of segmented polyurethanes and their permselectivity and permeability in the pervaporation separations of organic/organic mixtures and in the removal of VOC from water. The structural variations within this group of polymers were designed based on general physicochemical considerations and were achieved at the synthesis stage by using reagents of various chemical structures and molecular weights and in different initial molar ratios. Therefore, the homologous series of polyurethanes, having well defined and widely modified molecular structures, could be investigated. The pervaporation performances of the obtained polymers are described with respect to the various model binary mixtures simulating the feeds of commercial interest, like: benzene/cyclohexane mixtures with a low (5 wt. %) and a high (56 wt. %) benzene content, or benzene/water, ethanol/water, and acetone/water mixtures. The concept of a membrane material tailoring for a particular separation problem is also demonstrated.