The surface tunability and dye separation property of PVDF porous membranes modified by P(MMA-b-MEBIm-Br): effect of poly(ionic liquid) brush lengths

In order to obtain the tunable and charged surface of the membranes, polymerized ionic liquid(PIL) block copolymers poly (methyl methacrylate) (PMMA)-b-poly(1-[(2-methacryloyloxy)ethyl]-3-butylimidazoliumbromide) (PMEBIm-Br) with different poly(ionic liquid) brush lengths were synthesized by RAFT polymerization method and used in the fabrication of poly(vinylidene fluoride) blend membranes. Chemistry analysis confirmed the successful copolymerization of P(MMA-b-MEBIm-Br) with different chain lengths of PMEBIm-Br blocks, and the PIL groups was also detected on the surface of the blend membranes, which contributes to the hydrophilic and positively charged surface of the membrane. These properties were further enhanced by the chain length of PMEBIm-Br blocks in the copolymer. The surface wettability of the membranes can be regulated from hydrophilicity to hydrophobicity by anion exchange, and the water flux changes also confirmed these phenomena. In addition, the effects of PMEBIm-Br blocks on the separation properties of the membranes were investigated using two dyes, namely, orange G and rhodamine 6G. Results indicated that the blend membranes with long length of PMEBIm-Br blocks had high rejection and good antifouling property to rhodamine 6G. Furthermore, the adsorption experiment of the blend membranes to the two dyes also indicated that blend membranes with long length of PMEBIm-Br blocks would have good dye adsorption-separation property.