Ionic liquids for the control of the morphology in poly(vinylidene fluoride-co-hexafluoropropylene) membranes

The development of polymer membranes with tailored micro-morphology and wettability is a demand in the areas of filtration, sensors, and tissue engineering, among others. The thermoplastic copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), is one of the most widely used polymers for these applications due to its good mechanical and thermal properties, biocompatibility and low density. Although the control of the PVDF-HFP morphology is a complicated task, the introduction of ionic liquids (ILs) in the PVDF-HFP matrix opens new perspectives in this area. This work consists of a systematic study of three different protic ionic liquids ([dema][TfO], [MIm][NTf2] and [MIm][Cl]) in the control of PVDF-HFP membranes properties. Different preparation conditions are also analyzed. These results demonstrate how several parameters such as morphology, water absorption capacity and mechanical properties vary depending on the production methodology employed and on the choice of incorporated IL. Pores of different sizes, spherulites and compact structures have been obtained, as well as hydrophilic and highly hydrophobic structures. These results show that ILs play a key role in the optimization of polymer properties and given the large number of available ILs, open up new possibilities for the development of polymer membranes suitable for applications where specific morphologies are desirable.