Synthesis and characterization of a new hydrogel were. carried out using a chemically modified starch (starch-M) consisting of coupling C=C bounds coming from glycidil methacrylate (GMA) onto the polysaccharide structure. C-13 NMR, H-1 NMR, and FT-IR spectroscopies were used to confirm the incorporation of such groups onto the starch-M. The hydrogel was prepared by a crosslinking polymerization of starch-M using sodium persulfate as an initiating agent. The starch-M hydrogel shows morphology clearly different from that of the raw starch film due to the presence of, voids on its surface. The swelling process of the starch-M hydrogel was not significantly affected by changes on the temperature or on pH of the surrounding liquid, indicating the such behavior can be then understood by a diffusional process, resulting from its physical-chemical interactions with the solvent. The values of the diffusional exponent n were on the order of 0.45-0.49 for the range of pHs investigated, demonstrating that the water transport mechanism of starch-M hydrogel is more dependent on Fickian diffusion, that is, controlled by water diffusion. Such starch-M hydrogel is a promising candidate to be used in transporting and in preserving acid-responsive drugs, such as con ticoids, for the treatment of colon-specific diseases, for example, Crohn's disease. (C) 2008 Wiley Periodicals, Inc.46725672574