Methoxypolyethylene glycol grafting on polypropylene membrane for enhanced antifouling characteristics – Effect of pendant length and grafting density

• Clickable membrane prepared by photo bromination and SN2 nucleophilic substitution.
• Clickable methoxypolyethylene glycol (MPEG) prepared by Williamson reaction.
• Grafting density and pendant length play vital roles in membrane performance.
• High grafting density and long chain are bad for membrane permeability.
• High grafting density and long chain are conducive to fouling reduction.

Grafting density and pendant length are recognized as decisive roles in membrane performance; however, they are not easy to control in widely employed free radical grafting polymerization. Herein, methoxypolyethylene glycol (MPEG) brushes with predetermined chain lengths and grafting densities were prepared from hydrophobic macroporous polypropylene membrane (MPPM) by click chemistry.The grafting density of MPEG on the membrane rose with MPEG concentration and click reaction time, while with the decrease of pendent length. Under the same reaction conditions, the densities were 88.065, 13.116 and 7.070 chains/100 nm2 for MPEG-200/600/1000, respectively. The normalized pure water flux through MPEG-200 modified membrane (grafting density of 9.250 chains/100 nm2) was 222.0, twice that through the pristine one. Pearson correlation analysis indicates that the longer the pendent length and the higher grafting density are, the lower the normalized water fluxes of BSA solution and tap water are, while the better antifouling characteristics are.

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