Graft Copolymerization Onto Starch. 3: Grafting of Acrylamide Using Ceric Ion Initiation and Preparation of Its Hydrogels

Abstract

The grafting of acrylamide (AM) onto maize starch in aqueous medium initiated by ceric ammonium nitrate (CAN) has been studied gravimetrically under nitrogen atmosphere. The effect of concentration of monomer and initiator, polymerization time and reaction temperature has been studied in terms of efficiency of grafting (%GE) and percentage Add-on (%Add-on). The %GE was found to decrease with increase in monomer concentration, but the reverse trend was obtained on increasing the polymerization time and temperature. The maximum %GE was obtained at 45°C when polymerization was carried out for 180 min using [CAN] = 0.004 mol/L and [AM] = 0.141 mol/L in 100 mL of distilled water with 2 g of starch. These graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis. The graft copolymers showed enhanced thermal stability than pure starch. Hydrogels were prepared by grafting AM onto gelatinized maize starch followed by saponification of these graft copolymers with NaOH. The maximum water absorption obtained was 170 g/g.