Antifouling performance of poly(acrylonitrile)-based membranes: From green synthesis to application

In order to develop clean ultrafiltration membranes able to prevent the fouling of biological compounds in filtration processes, poly(ethylene glycol) methyl ether acrylate (PEGA) was grafted to poly(acrylonitrile) (PAN) by free-radical polymerization in supercritical carbon dioxide (scCO₂) and the grafted copolymer was blended with PAN to fabricate porous membranes using scCO₂-induced phase inversion method. Fourier transform infrared (FT-IR) analysis, ¹H nuclear magnetic resonance (¹H NMR) and differential scanning calorimetry (DSC) confirmed that the poly(acrylonitrile)-graft-poly(ethylene oxide) (PAN-g-PEO) was successfully synthesized, for the first time, in scCO₂. The effect of increasing PEGA content on the initial monomer feed mixture on graft polymer morphology and average molecular weight was studied. Blended membranes with different PEGA contents were investigated by scanning electron microscopy (SEM), mercury porosimetry and dynamical mechanical analysis (DMA) to characterize their morphological, physico-chemical and mechanical properties. Moreover, water contact angle measurements, pure water permeability and filtration experiments were performed to evaluate membrane hydrophilicity and fouling resistance properties. Permeation experiments of model foulants, bovine serum albumin (BSA) and starch solutions were used to investigate antifouling character of blend membranes at different pHs. PAN:PAN-g-PEO (70:30) showed to be the ultrafiltration membrane with best performance. Furthermore, comparing with conventional technologies blended membranes of PAN:PAN-g-PEO prepared by a scCO₂-assisted process showed enhanced hydrophilicity, larger protein and starch solution permeabilities and good resistance to irreversible fouling, indicating that the technology is an efficient process to prepare fouling resistant membranes for biomacromolecule separations.