Graft copolymerization of acrylamide onto carboxymethyl starch

Water absorption resins of carboxymethyl starch graft acrylamide (CMS-g-AM) were synthesized by copolymerization based on a free radical reaction. At first, CMS was prepared with starch and chloroacetic acid in an alkali-methanol media. Then, AM was grafted onto CMS by using ceric ammonium nitrate as an initiator. The resulting graft products were identified by infrared spectra. The effects of the preparation conditions on the substituent degree (SD) of starch and the water absorption capacities of CMS-g-AM were investigated. The results showed that SD of starch first increased remarkably and then decreased gradually with increased addition of sodium hydroxide, and the water absorption capacity of CMS-g-AM depended greatly on the SD of CMS and its maximum with 0.75 of SD of starch was 350 g/g.