Effects of methacrylate based amphiphilic block copolymer additives on ultra filtration PVDF membrane formation

Abstract

Well-defined methacrylate based amphiphilic block copolymers (BCs) consisting of poly(methyl methacrylate) (PMMA) and poly(ethylene glycol) methacrylate (PPEGMA) were synthesized by atom transfer radical polymerization (ATRP) and used as additives in DMAc casting solution to fabricate poly(vinylidene fluoride) (PVDF) ultra-filtration (UF) membranes in non-solvent induced phase separation (NIPS) process, where the amphiphilic BC additives hydrophilically altered PVDF with PPEGMA block segment by strong interaction with the other PMMA block segment, which reduced water resistance to the PVDF polymer solution during phase separation. FT-IR and XPS studies showed carbonyl groups of BCs in the PVDF membranes, which were not changed even after IPA treatment, indicating that BCs in the membrane were very stable. Obtained PVDF membranes with BCs showed porous surface layer and finger-like pore structures with macrovoids on the sublayers, of which sizes were increased with the increase of BC contents, which were then compared to the pristine PVDF membranes and the PVDF membrane with corresponding other additives such as hydrophobic PMMA, hydrophilic PPEGMA, LiCl and BC/LiCl. Obtained PVDF membranes showed MWCO with 100 K PEO and the best water flux (140 LMH) was achieved in the PVDF membrane with BC/LiCl additive, which was almost 4 times higher than the pristine PVDF membrane. In addition, the PVDF membranes with BC and BC/LiCl additives improved the anti-fouling property for BSA protein, of which reversible fouling resistance ratio was ca. 7 times higher than that of the pristine PVDF membrane.