Preparation of Porous Polysulfone Membranes Using Ionic Liquids with Different Alkyl Chain as Additives

Abstract

1-alky-3-methylimidazolium hexfluorophosphate ([n-Cnmim][PF6]) and 1-alky-3- methylimidazolium thiocyanate ([n-Cnmim]SCN) (n=4,8,16) were firstly introducing into the casting solution (PSF/NMP), porous polysulfone (PSF) membranes were successfully prepared by the wet-phase-inversion. The scanning electron microscope was utilized to visualize the cross-sections of the membranes, in order to study the influence of ionic liquids with different alkyl chain on the porous structures. The results indicate that the PSF membranes have different structures and separation properties due to ionic liquids with different alky chain. For ionic liquids with the short alkyl chain, the prepared membranes have the porous structure on cross-sections, but no or weak separation properties. However, for ionic liquids with the long alkyl chain, the prepared membranes have both porous structure and good separation properties. According to the structure of a hydrophobic straight-long alkyl and a hydrophilic limidazolium ring, the ionic liquid with long alkyl chain is considered as a surfactant, it can change not only the interface properties between the casting solution and coagulation bath, but also induce the space structures of the polymer chains.