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

Volumetric shrinking kinetics of poly (N-isopropylacrylamide-co-acrylic acid) hydrogels in response to Cu^(2+) solution

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。

The copolymer（N-isopropylacrylamide-co-acrylic acid,NIPAAm-co-AA） was synthesized by the microwave irradiation method and its volumetric shrinking kinetics in Cu^2＋ 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 Cu^2＋ 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 Cu^2＋ concentration in solution.Their response activation energies in the range of 36-42 kJ·mol^-1 decreased with increasing Cu^2＋ concentration at a temperature between 40—60℃.The regeneration experiment showed that the copolymer hydrogels could shrink/swell in response to temperature-swing in Cu^2＋ 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.