Graft copolymerization, characterization, and degradation of cassava starch-g-acrylamide/itaconic acid superabsorbents

Biodegradable superabsorbent polymers were synthesized by graft copolymerization of acrylamide (AM)/itaconic acid (IA) onto cassava starch via a redox initiator system of ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED), in the presence of N,N'-methylenebisacrylamide (N-MBA) crosslinking agent, sodium bicarbonate foaming agent, a triblock copolymer of polyoxyethylene/polyoxypropylene/polyoxyethylene as a foam stabilizer. The acrylamide-to-itaconic acid ratio, the starch-to-monomer ratio, and concentrations of the crosslinking agent and initiator, on the water absorption of the superabsorbent polymers were investigated. The swelling of starch-g-PAM was 39 g g(-1) while the starch-g-P(AM-co-IA) with the IA content of 0.02-0.15% mole gave the water swelling value in the range of 70-390 g g(-1). By-products of the reaction were removed by water extraction. The starch grafted composites were characterized by FTIR and SEM. Thermal gravimetric analysis was also used for determining the percentage of grafting ratio. Biodegradation of the starch grafted copolymer was carried out using alpha-amylase. After the alpha-amylase hydrolysis, the amount of reducing sugar was quantified by DNS method. The hydrolyzed solution gave a negative test with iodine solution and a positive test by Benedict's solution, an indication of the existence of glucose units. (c) 2006 Elsevier Ltd. All rights reserved.