Chapter 5: Ion-recognizable Smart Gating Membranes

This chapter introduces ion-recognizable smart gating membranes in terms of their design, production and performance as well as applications. First, the design and fabrication of ion responsive membranes possessing functional gates comprising poly(N-isopropylacrylamide) chains as actuators and crown ether units as ion sensors are described. Then, two types of ion-recognizable membranes with positively and negatively responsive properties are introduced. In the presence, or with an increase, of ions in the environment, the positively-responsive gating membrane's permeability increases; meanwhile, the negatively-responsive gating membrane exhibits the opposite performance. Finally, the prospective for potential conundrums in the progress and industrial application of ion-recognizable smart or intelligent gating membranes is discussed.