Amphipathic Janus Membrane with Hierarchical Multiscale Hyperporous Structure for Interfacial Catalysis

Abstract

The rational design and realization of multiscale porous structures has been a long-standing challenge in membrane science. Block copolymers (BCPs) with their self-assembly-enabled nanodomains have the potential to make structural breakthroughs. An amphipathic Janus membrane, with a hierarchical multiscale hyperporous structure constituted by polystyrene-b-poly(4-vinylpyridine) (PS4VP) and polyvinylidene fluoride (PVDF) blocks, was designed and synthesized in this work. Hydrophobic PVDF dominated one side of the membrane, and hydrophilic PS4VP, with nanopores that formed inside the macroporous channels of PVDF via a self-assembly approach, dominated the other side. Candida Rugosa Lipase (CRL), as a model biocatalyst, was immobilized in the PS4VP nanopores via injection. The immobilized lipase was exactly suspended at the interface of the organic and aqueous phases, owing to the amphipathic property of the Janus membrane. The designed structures and catalysis performances were further characterized. The immobilized lipase exhibited a three times higher specific activity than free lipase, and the relative activity still remained above 90% after 10 cycles of reusing, indicating the observable promotion and the guaranteed stability of the Janus membrane in interfacial catalysis. This work provided a general, facile and unique example for the design and synthesis of a hierarchical multiscale hyperporous membrane for interfacial catalysis.