The copolymer (N-isopropylacrylamide-co-acrylic acid

NIPAAm-co-AA) was synthesized by the microwave irradiation method and its volumetric shrinking kinetics in Cu2+ aqueous solution was investigated in this paper.The volumetric shrinking kinetic constants and the activation energies for these copolymer hydrogels were estimated from their kinetic data.Furthermore

a mathematic model was established to describe the relationship between Cu2+ concentration and volumetric shrinking kinetic rate constant of copolymer hydrogels.The results indicated that the volumetric shrinking kinetics of these copolymer hydrogels was found to follow the pseudo-first-ordered kinetics.Moreover

their volumetric shrinking kinetic rate increased with increasing Cu2+ concentration in solution.Their response activation energies in the range of 36－42 kJ8226;mol-1 decreased with increasing Cu2+ concentration at a temperature between 40—60℃.The regeneration experiment showed that the copolymer hydrogels could shrink/swell in response to temperature-swing in Cu2+ solution sensitively after shrinking (at 50.0℃)/swelling (at 6.0℃) for three times continuously.The tiny change of their shrinking/swelling ratio in the regeneration experiment showed a good repetition of hydrogel in response to temperature.