Positively K+-Responsive Membranes with Functional Gates Driven by Host–Guest Molecular Recognition



A novel positively K+-responsive membrane with functional gates driven by host-guest molecular recognition is prepared by grafting poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) (poly(NIPAM-co-AAB15C5)) copolymer chains in the pores of porous nylon-6 membranes with a two-step method combining plasma-induced pore-filling grafting polymerization and chemical modification. Due to the cooperative interaction of host-guest complexation and phase transition of the poly(NIPAM-co-AAB15C5), the grafted gates in the membrane pores could spontaneously switch from “closed” state to “open” state by recognizing K+ ions in the environment and vice versa; while other ions (e.g., Na+, Ca2+ or Mg2+) can not trigger such an ion-responsive switching function. The positively K+-responsive gating action of the membrane is rapid, reversible, and reproducible. The proposed K+-responsive gating membrane provide a new mode of behavior for ion-recognizable “smart” or “intelligent” membrane actuators, which is highly attractive for controlled release, chemical/biomedical separations, tissue engineering, sensors, etc.