Regulating the Interlayer Spacing of 2D Lamellar Polymeric Membranes via Molecular Engineering of 2D Nanosheets

The recent development of 2D lamellar membranes may lead to the next generation of membrane processes for molecular separation, but smart regulation of substance permeability has rarely been reported for the challenge of precise regulation of the interlayer spacing (d-spacing). Here 2D lamellar polymeric membranes with reversible thermoresponsive nanogating regularity are constructed by regular stacking of poly(N-isopropylacrylamide) (PNIPAM) brushes covalently grafted hybrid nanosheets (HNS-P). HNS-P were formed under precise molecular engineering of in situ surface-initiated photopolymerization of NIPAM on the surface of hybrid nanosheets (HNS), which were fabricated by crystal-driven self-assembly. The uniform, square HNS-P with a tunable PNIPAM brush made it possible to obtain a highly ordered lamellar membrane and enhance the interfacial compatibility of the sheets for the membrane. Moreover, the interspace tunability generated by adjusting the environment temperature or the surface grafting ratio of PNIPAM brushes endowed the membrane with a high gating ratio (∼8.5) of water permeance and the ability to separate multiple gradient molecules of different sizes. This integrated assembly strategy provides insight into the formation of 2D lamellar polymeric membranes and expands the scope of smart gating membranes, showing promising applications in micro/nanofluidics and molecular separation.