Modulation the morphologies and performance of polyacrylonitrile-based asymmetric membranes containing reactive groups: Effect of non-solvents in the dope solution

Previous work revealed that polyacrylonitrile-based membranes containing reactive groups could be facilely modified through chemical reactions to improve their surface properties meeting the demands of hemodialysis and/or enzyme immobilization. One should keep in mind that, with the exception of surface properties, the morphologies and permeation performances of these potential membranes must be modulated also. In this work, using water and water–PEG (PEG400 or PEG200) or water–glycerin mixture as non-solvent additive respectively, the morphologies and permeation performances of poly(acrylonitrile-co-acrylic acid) (PANCAA) asymmetric membrane, which was prepared by the dry–wet phase-inversion process, were investigated on the basis of scanning electron microscopy, water permeation, and bovine serum albumin (BSA) rejection measurements. Falling ball method was used to measure the gelation rate of the dope solution. It was found that the non-solvents used could induce the gelation of dope solution before immersion, thus suppressed the formation of macrovoids effectively. Results revealed that: (1) increasing the water and water–PEG (or glycerin) mixture concentration modulated the cross-section of the PANCAA membrane experiencing from finger-like to sponge-like voids and (2) glycerin–water mixture induced the gelation more readily than PEG200–water mixture, while PEG200 than PEG400. Moreover, in the case of more non-solvents addition, higher water flux and lower BSA rejection rate could be achieved, while at appropriate amount of water, lowest flux would be obtained.