Preparation and properties of composite membranes of fully fluorinated nanofibrous electrospun mat impregnated with highly sulfonated polysulfone: Effect of thermal treatment on the mat and the membranes thereof

Abstract

To prepare highly sulfonated/fully fluorinated nanofibrous composites, sulfonated polysulfone with 70% degree of sulfonation and fully fluorinated poly(aryl ether) are synthesized as components. Nucleophilic aromatic substitution reaction is applied for polymerization. Then, the composite membrane with thickness of 60 μm and 30 wt% electrospun nanofibers is prepared via impregnation of the fully fluorinated mat by a suitable solution of the sulfonated polymer. In the next step, two treated composite samples with thicknesses of 60 and 20 μm containing 20 wt% of treated electrospun nanofibers are also prepared by impregnation. A simple thermal treatment on fully fluorinated mat is used to obtain the latter composites. The thermal crosslinking make the handling of the thin mat possible. Fourier transform infrared spectroscopy, solubility assessment, and gel content measurement are used to confirm thermal crosslinking. The properties of three developed composites are studied to investigate the presence of fluorinated electrospun nanofibers, thermal treatment effectiveness, and nature of the thin membrane structure. The remarkable tensile strength of 87.52 MPa is attained for the thin membrane. Moreover, the conductivity value of 0.146 S/cm at 30 °C with an activation energy of 10.22 kJ/mol in this sample is motivating.