In this study, a novel semi-interpenetrating polymer network (semi-IPN) hydrogel of kappa-carrageenan-g-poly(methacrylic acid)/poly(N,N-diethylacrylamide) (KC-g-PMAA/PDEA) was prepared using ammonium persulfate as an initiator and N,N,N',N'-tetramethylethylenediamide as an accelerator at 25 degrees C. The structure of the hydrogels was characterized by Fourier transform infrared spectroscopy and scanning electron microscope. The effects of the feed components, temperature and pH on the swelling behavior of the hydrogels were studied. The results showed that the introduction of KC-g-PMAA did not change the lower critical solution temperature of the semi-IPN hydrogels, which was the same to the PDEA hydrogel (at 28 degrees C). With the increase of KC-g-PMAA content, the thermo- and pH-sensitivity of the hydrogel improved, which the swelling rate increased with the increasing content of KC-g-PMAA. The semi-IPN hydrogels showed a fast deswelling and swelling rate. The swelling dynamic transport of the hydrogels was analyzed based on the Fickian equation. (C) 2008 Elsevier B.V. All rights reserved.