温度及pH敏感聚(丙烯酸)/聚(N-异丙基丙烯酰胺)互穿聚合物网络水凝胶的合成及性能研究

合成聚（丙烯酸）／聚（Ｎ 异丙基丙烯酰胺）互穿聚合物网络（ＰＡＡｃ／ＰＮＩＰＡＩＰＮ）水凝胶，具有温度及ｐＨ双重敏感特性．这种水凝胶在弱碱性条件下的溶胀率远大于酸性条件下的溶胀率．在酸性条件下，随着温度上升，凝胶的溶胀率也随之逐渐上升；而在弱碱性条件下，温度低于聚（Ｎ 异丙基丙烯酰胺）（ＰＮＩＰＡ）的较低临界溶解温度（ＬＣＳＴ）时，溶胀率也随着温度的上升而上升，当温度达到ＬＣＳＴ时，凝胶的溶胀率突然急剧下降，并随着温度的逐渐上升而下降．

THE SYNTHESIS AND CHARACTERIZATION OF TEMPERATURE AND pH SENSITIVE POLY(ACRYLIC ACID)/POLY-(N-ISOPROPYLACRYLAMIDE)IPN HYDROGEL

The aqueous solution of Poly(N isopropylacrylamide) (PNIPA) exhibits a lower critical solution temperature(LCST,32℃).Its hydrogel undergoes phase separation as the temperature is raised above LCST.This temperature sensitive hydrogel has been widely used in many fields,for instance,controlled drug release,enzyme immobilization and release of solutes.However,response to pH of hydrogel may be required at the same time for some applications.Here, a new intelligent hydrogel which can respond to temperature and/or pH changes is described.The new hydrogel was prepared by using interpenetrating polymer networks(IPN) technique.Poly(acrylic acid)/Poly(N isopropylacrylamide)(PAAc/PNIPA)IPN hydrogel was synthesized.The temperature and pH sensitivity of this hydrogel was studied.The Swelling Ratio(SR) of this hydrogel in weak alkaline solution is much greater than that in acidic solution.Experimental results revealed that its SR rises as the temperature is raised in acidic solution.On the other hand,in weak alkaline solution,when the temperature is below the LCST of PNIPA (32℃),the SR of the hydrogel also rises as the temperature is raised.However,when he temperature reachs the LCST or higher,its SR slumps suddenly and drops quickly.This IPN hydrogel may be useful in the field of controlled drug delivery.