Abstract

The grafting of poly(acrylic acid) and/or acrylamide onto biopolymer chitosan were carried in order to obtain hydrogel materials. The grafting reactions were carried out in a homogeneous aqueous phase by using potassium persulfate in combination with ferrous ammonium sulfate as redox initiator system in the case of acrylic acid and potassium persulfate alone in the case of acrylamide. The percentage of grafting was found to depend on the relative amount of monomer to chitosan, initiator and ferrous ion concentration, volume of the aqueous phase as well as reaction time and reaction temperature. In the case of acrylic acid a maximum grafting of 1800% was obtained, whereas with acrylamide the optimum percentage of grafting attained was near 400%. Evidence of grafting was obtained from comparison of FTIR of the grafted and ungrafted chitosan as well as solubility characteristics and swelling behavior of the products. The swelling degree of the grafted chitosan samples was determined at two different pH values. The percentage of grafting influenced the degree of swelling of the grafted chitosan, in different manner depending on the nature of the grafted chains, where values as high as 40 was observed.