聚(N-异丙基丙烯酰胺-co-丙烯酸)水凝胶对铜离子的体积响应动力学

采用微波辐射法制备了N-异丙基丙烯酰胺-co-丙烯酸共聚水凝胶，探讨了该水凝胶对Cu²⁺的响应动力学，并估算出此过程中水凝胶的体积收缩速率常数及其反应活化能，同时建立了Cu²⁺浓度对水凝胶体积收缩响应速率常数影响的数学关系模型。实验结果表明，水凝胶对Cu²⁺所产生的体积收缩响应符合拟一级动力学反应。在40～60℃水溶液中，水凝胶的收缩速率随溶液中Cu²⁺浓度的增高而加快，其反应活化能在36～42 kJ•mol^-1之间，且随着溶液中Cu²⁺浓度的增大而逐渐减小。重复性实验表明，该共聚水凝胶经过3次体积收缩(50.0℃溶液)/溶胀(6.0℃溶液)的循环实验，它在含Cu²⁺水溶液中对温度变化仍能保持高灵敏度的体积收缩/溶胀响应，而且其3次体积收缩/溶胀响应值几乎一样，有很好的重现性。

Volumetric shrinking kinetics of poly(N-isopropylacrylamide-co-acrylic acid)hydrogels in response to Cu2+ solution

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 kJ•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.