A combined physical blending and surface grafting strategy for hydrophilic modification of polyethersulfone membrane toward oil/water separation

Abstract

The block copolymer, Pluronic F127-block-poly(acrylic acid) (PAA-b-F127-b-PAA) was firstly synthesized via RAFT polymerization. Then, the copolymer was utilized as the blending modifier for fabricate polyethersulfone (PES)/PAA-b-F127-b-PAA composite membrane by nonsolvent induced phase separation technique. The hydrophilic PAA segments were concentrated onto the membrane surface due to the surface segregation phenomenon in the membrane formation process, which improved the hydrophilicity of the membrane surface and provided active sites for further surface grafting modification. Subsequently, the amine-terminated poly(sulfobetaine methacrylate) (NH2-PSBMA) was prepared through ARGET ATRP and used as surface modifier to fabricate PES/PAA-b-F127-b-PAA/PSBMA composite membrane by amination reaction. The composite membrane exhibited the highest pure water flux and oil flux around 358.25 and 217.53 L m−2 h−1, which equal to 5.6 times and 19.6 times of unmodified PES membrane respectively. The flux recovery rate increased from 45.74% to 94.64%, suggesting the fouling-resistance of the composite membranes was greatly improved. The hydrophobic PPO segments of PAA-b-F127-b-PAA used as anchor segments and amalgamated with PES molecular by hydrophobic interaction and physical intertwisting, resulting in the PAA-b-F127-b-PAA was firmly embedded in the membrane. Moreover, the PSBMA segments were grafted onto the membrane surface by forming strong chemical bonds, exhibiting excellent stability. It shows that this membrane material prepared by physical blending and surface grafting has a good application prospect in oil/water separation.