Modified carrageenan. 1. H-CarragPAM, a novel biopolymer-based superabsorbent hydrogel

A novel kappa-carrageenan (kappa C)-based superabsorbing hydrogel was synthesized through graft copolymerization of acrylamide (AAm) onto a kappa C substrate in the presence of a crosslinking agent. The crosslinked kappa C-poly(AAm) polymer graft was partially hydrolyzed in alkaline medium to yield a superabsorbent resin, H-carragPAM. The resin structure was confirmed using FTIR spectroscopy. The variables of graft copolymerization (monomer, initiator, polysaccharide and crosslinker concentration, reaction temperature and time as well as stirrer speed) that affected on the ultimate water-swelling capacity were optimized. The time-temperature variation of the copolymerization was investigated in terms of the absence and presence of the atmospheric oxygen. Under optimized conditions, the maximum capacity of swelling in distilled water and saline (0.9 wt% NaCl) were 1,465 and 121 g/g, respectively. Since this hydrogel exhibited a very high absorptivity in saline, it may be referred to as low salt sensitive superabsorbent.