Low Fouling Molecular Selective Channels through Self-assembly of Cross-linked Block Copolymer Micelles for Selective Separation of Dye and Salt

Abstract

We report the solvent-evaporation and ionic cross-linking mediated self-assembly of the shell cross-linked micelles of the amphiphilic triblock copolymer containing middle poly(methyl methacrylate) block (hydrophobic) and poly(2-dimethylamino)ethyl methacrylate end blocks (hydrophilic) on the membrane substrate to create molecular selective channels. The formation of selective channels on the substrate is attributed to the local increase of micelle concentration upon solvent evaporation, which leads to the core–core hydrophobic interaction. The post-ionic cross-linking of the shell part further reduces the intermicelle distance, thereby creating interstices for selective separation. The TUF-1:1 membrane prepared by the self-assembly of the cross-linked micelles (triblock copolymer:halide-terminated PEG-based = 1:1 w w^–1) and by the post-ionic cross-linking shows molecular weight cutoff of 3000 g mol^–1 and pure water permeance of 52 L m^–2 h^–1 bar^–1. The membrane shows 99.5–99.9% rejection of Congo red and Direct red-80 in the presence or absence of salts and Na₂SO₄ to dye separation factor of about 900. The added functionality (PEG) in the micelle structure provides good fouling-resistant properties toward dye and bovine serum albumin. This work provides the membrane formation mechanism and the advantages of the membrane for fractionation and resource recovery applications.