A crown ether derivative (4'-allyldibenzo-18-crown-6, CE) was covalently incorporated into the network of temperature sensitive poly(Nisopropylacrylamide) (PNIPA) hydrogels by copolymerization in a mixed solvent of water and tetrahydrofuran (H2O/THF). The poly(Nisopropylacrylamide-co-4/-allyldibenzo-18-crown-6) (poly(NIPA-co-CE)) hydrogels exhibited dramatically faster deswelling rates than normal PNIPA hydrogels at a temperature (50 degreesC) above their lower critical solution temperatures. The effect of the solvent component ratio in the mixed solvent during the copolymerization on the swelling properties of the poly(NIPA-co-CE) hydrogel was investigated. The thermosensitive poly(NIPA-co-CE) hydrogels have potential applications in the extraction of cations and separation of chiral drugs.