Metal ions play an important role in life activities

but some heavy metal ions (such as Pb2+ and Hg2+) have high toxicity to the organisms even at alow concentration.It is of important theoretical significance and great practical interest to study smart materials with metal ion-recognition properties. Crown ethers have remarkable recognition ability towards specific mental ions.A series of ion-recognition-responsive smart materials composed of crown ethers and responsive poly (N-isopropylacrylamide) (PNIPAM) polymer have been developed.The development of ion-recognition-responsive smart materials based on 18-crown-6 and 15-crown-5 is reviewed.At present

the ion-recognition-responsive smart materials are still at the basic research stage and need further intensive study and development.