Synthesis and characterization of fast responsive thermo- and pH-sensitive poly[(N,N-diethylacrylamide)-co-(acrylic acid)] hydrogels

BACKGROUND: A considerable amount of research has been focused on smart hydrogels that can respond to external environmental stimuli, especially temperature and pH. In this study, fast responsive thermo- and pH-sensitive poly[(N,N-diethylacrylamide)-co-(acrylic acid)] hydrogels were prepared by free radical copolymerization in aqueous solution using poly(ethylene glycol) (PEG) as a pore-forming agent. RESULTS: Swelling studies showed that the hydrogels produced had both temperature and pH sensitivity. The deswelling kinetics at high temperature demonstrated that the shrinking rates were influenced by the addition of the pore-forming agent and the amount of acrylic acid in the initial total monomers. The deswelling curves in low-buffer solutions had two stages. Pulsatile swelling studies indicated that the PEG-modified hydrogels were superior to the normal ones. These different swelling properties were further confirmed by the results of scanning electron microscopy. CONCLUSION: Such fast responsive thermo- and pH-sensitive hydrogels are expected to be useful in biomedical fields for stimuli-responsive drug delivery systems. (C) 2008 Society of Chemical Industry