Fabrication of novel temperature and pH sensitive poly (N-isopropylmaleamic acid-co-acrylonitrile) hydrogels

To combine temperature and pH sensitive capabilities, N-isopropylmaleamic acid (NIPMMA), having isopropylamide group and weakly acidic group (–COOH), was synthesized and used as a precursor for fabrication of temperature and pH sensitive hydrogels. In this paper, a new class of intelligent hydrogel with pH and temperature sensitivity originated from only one precursor (NIPMMA) was designed and demonstrated. Resultant poly(NIPMMA-co-acrylonitrile) [P(NIPMMA-co-AN)] hydrogels were characterized by Fourier transform infrared spectroscopy for structural determination and scanning electron microscope for morphology observation. Their temperature and pH sensitive behaviors were also examined in detail. The data obtained exhibited that the magnitude of sensitive properties of P(NIPMMA-co-AN) hydrogels depended on the composition ratio of two precursors. By increasing the content of NIPMMA, the temperature and pH sensitive capabilities of P(NIPMMA-co-AN) hydrogels were improved correspondingly since AN has no sensitivity upon temperature or pH changes.