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 ‐AAB 15 C 5 )) 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 ‐AAB 15 C 5 ), 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 + , Ca 2+ or Mg 2+ ) 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.