Smart Gating Membranes with K+-Responsive Pore Size and Surface Property

A novel smart gating membrane with K⁺-responsive pore size and surface property 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) copolymer, not only the membrane pores with grafted gates could spontaneously switch from “closed” state to “open” state, but also the membrane surface is induced the hydrophilic/hydrophobic change of the membrane surface 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, sensors, etc.