'Button and Buttonhole' Supramolecular Structure Enables the Self-Healing Behaviors of Functionalized Poly(ether sulfone) Membranes for Osmotic Power Generation

Osmotic power generation has emerged as an advanced technology toward water-energy nexus to tackle global water pollution. It provides a sustainable use of salinity gradient from water resources yet encounters major obstacles caused by pressure-retarded osmosis (PRO) membrane fouling. Although membranes with good antifouling properties are widely studied, their antifouling functions are readily lost when scratches or detachments occur through physical damage during operation and chemical degradation by water and corrosive foulants. Consequently, it is important to develop antifouling membranes with autonomous self-healing capabilities. Herein, self-healable functionalized poly(ether sulfone) (PES) antifouling membranes have been fabricated via the sequential conjugation of the zwitterionic random copolymer [poly(1-(1-(1-adamantylcarbonyloxy)methyl)-3-vinylimidazolium bromide-co-1-(3-sulfopropyl)-3-vinylimidazolium-co-vinylamine)] (P(ADVI-co-SBVI-co-VA), abbreviated as PASV copolymer) and linear cyclodextrin polymer (LPCD) on polydopamine-preactivated PES supports. The self-healing behaviors rely on the judiciously designed "button-and-buttonhole" supramolecular network. Specifically, β-cyclodextrins in LPCD and adamantines in PASV act as "buttonholes" and "buttons", respectively. Under physical and chemical damages, the β-cyclodextrin "buttonhole" may sacrificially detach from the adamantine "button" of PASV but then recap another adamantine to restore the protective function. The antifouling and self-healing traits of as-functionalized PES-g-PASV-LPCD membranes were demonstrated by the superior antiprotein behaviors and improved antimicrobial performances on both nonaged and aged samples. In the PRO process, the modified membranes were effective in mitigating organic fouling and exhibited higher power density (79% of the initial value) than the nonmodified ones (47% of the initial value) in municipal wastewater testing. The strategy for engineering inherently healable and antifouling membranes paves a new pathway for the development of sustainable membranes for osmotic power production.