Poly(maleic anhydride-co-acrylic acid)

P(MA-AA)

was synthesized by the free-radical copolymerization of maleic anhydride with acrylic acid

and fast responsive pH-sensitive poly(maleic anhydride-co-acrylic acid)/polyethylene glycol

P(MA-AA)/PEG

hydrogels were prepared using PEG as macromolecular cross-linking agent. FT-IR and 1H-NMR spectrometry were applied to characterize the structure of P(MA-AA). The influences of pH and ionic strength on the swelling behavior of P(MA-AA)/PEG hydrogels and the swelling-deswelling changes along with the repeated changes between acid and alkali conditions were studied. The results showed that there was a hundredfold difference in the swelling ratios between the conditions of acid and alkali

and the swelling capability could not be weakened after multiple swelling-deswelling cycles. The results of swelling kinetics demonstrated that the response rate of P(MA-AA)/PEG hydrogels was very fast

because the swelling transition points always occurred at 10 min. The pH-responsive hydrogels reported here might be a smart material for potentially applications in many areas

including biosensors

drug-delivery devices and tissue engineering.