The FTIR spectra of starch and starch-g-poly(acrylic acid) hydrogel are shown in Fig.2.The FTIR spectra of starch (Fig.2 a) show the O-H stretching absorption in the region of 3421.24cm-1,the C-H stretching at 2930.28cm-1,C=O stretching at 1647cm-1 and the triplet band for the C-O-C stretching absorption at 1158.50cm-1,1080.84cm-1.Although the FTIR spectra of starch-g-poly(acrylic acid) hydrogel (Fig.2 b) present the absorption bands which are characteristics of the starch backone at 3439.74cm-1,2939.78cm-1,1157.34cm-1 and 1082.04cm-1,all of them becomeweaker.Fig.2 FTIR spectra of the native starch and starch-g-poly (acrylic acid) hydrogel.(a) nativestarch,(b)starch-g-poly(acrylicacid)hydrogel In addition, the absorption bands at 1647.48cm-1 attributed to C=O bending from starch disappeared after the grafting reaction.An additional sharp peak at 1711.32cm-1 belonging toC=O stretching of the carboxylic groups ofthe grafted poly(acrylic acid) chains can be observed in the Fig2 b. The presence of above information in the starch-g-poly (acrylic acid) hydrogel confirms the grafting of acrylic acid onto starch. Earlier reports on the graft copolymerization of starch with acrylic acid support this conformation