纤维素基水凝胶的溶胀动力学研究

以纤维素为骨架,丙烯酸(AA)为单体,采用接枝共聚方法在85%磷酸溶液反应介质中合成了pH值敏感水凝胶(C-g-AA)。主要研究了C-g-AA水凝胶的pH值敏感性及在不同pH值溶液(pH值分别为1.15,6.86,11.05)中的溶胀可逆性和溶胀动力学行为,并与在去离子水中的溶胀行为进行对比。结果表明,C-g-AA水凝胶的溶胀比随着凝胶中AA组分的增加而增加,最高可达73%;水凝胶溶胀具有明显的pH值敏感性,当pH值>7时达到溶胀平衡,水凝胶对pH值的溶胀可逆性良好;不同pH值溶液中的溶胀动力学表明,溶胀初期水分子在水凝胶中的扩散行为可用non-Fickian扩散定律来描述,整体溶胀行为满足Schott二级动力学方程,而在去离子水中,水凝胶溶胀初期的扩散特征指数同样保持稳定,但整体溶胀行为却不遵循Schott二级动力学方程。

Study on the Swelling Kinetics of pH-sensitive Cellulose-based Hydrogels

Cellulose-graft-acrylic acid(C-g-AA) hydrogels were prepared via graft polymerization in 85% phosphoric acid solution,the pH sensitivity and reversibility,salt sensitivity and swelling kinetics of the hydrogels were tested.The results showed that the hydrogels had obvious pH sensitivity,the swelling reached equilibrium when pH>7,and the hydrogels also displayed excellent pH reversibility.The swelling ratio in distilled water was increased with increasing of AA components in hydrogels,and could reached 73% with mole ratio of 6∶ 1(AA/cellulose).The swelling kinetics in the solutions with various pH values indicated that the initial water intake of hydrogels followed a non-Fickian type diffusion with the diffusion exponents all higher than 0.5,and the whole swelling process fit the Schott model well.In distilled water,the initial water intake also followed a non-Fickian type diffusion,while the whole swelling did not obey the Schott swelling kinetic model.