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

Abstract

The development of polymer membranes with tailored micro-morphology and wettability are a demand in the areas of filtration, sensors or tissue engineering, among others. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is a thermoplastic copolymer and one of the most interesting polymers to be used in these areas due to its good mechanical and thermal properties, biocompatibility and low density. The control of the morphology on this material is crucial for its performance [1]. However, for the moment this is a complicated task and is mostly restricted to the use of solvent evaporation (SE) and non-solvent-induced phase separation (NIPS) techniques. In this way, this work consists in a systematic study of the use of ionic liquids in the control of these membranes properties. Ionic liquids are molten salts with melting points lower than 100 °C, which stand out for their good properties, such as high good thermal stability, low vapor pressure, nonflammability and their ability to act as solvents of various materials and they have already been studied for the control of morphology in certain materials [2-3]. In this work, the production and the characterization of PVDF-HFP@ionic liquid composite membranes using different ionic liquids (Diethylmethylammonium trifluoromethanesulfonate, 1-Methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-Methylimidazolium chloride) and methodologies (solvent evaporation temperature) are described in detail. The results demonstrate how aspects such as morphology, wettability or mechanical properties change depending on the production methodology employed and on the type of used ionic liquid. In view of the results, it is concluded that the morphology of a polymer composite can be tuned by use ILs and this control of the morphology could open up new possibilities for their use in different applications.