Synthesis and characterization of novel biodegradable superabsorbent hydrogels based on chitin and succinic anhydride

Synthesis of novel superabsorbent hydrogels has been investigated with the reaction of chitin and succinic anhydride (SA) in the presence of 4-dimethylaminopyridine as esterification catalyst in mixture of tetrabutylammnium fluoride and dimethylsulfoxide (TBAF/DMSO) or in mixture of lithium chloride and N-methyl-2-pyrrolidinone (LiCl/NMP), followed by NaOH neutralization. Interestingly, hydrogel was obtained in TBAF/DMSO without any crosslinking agent, which indicated the partial formation of diester between hydroxyl group of chitin and SA. On the contrary, products obtained in LiCl/NMP dissolved out during the absorbency test, which indicates that they consist mainly of linear polymer. The former absorbed water about 300 times of its dry weight, which is comparable with the conventional sodium polyacrylate superabsorbent hydrogel. Further, in aqueous NaCl solution, absorbency of the product hydrogels was higher than the sodium polyacrylate superabsorbent hydrogel. The products biologically degraded up to 70% after 20 days, which shows their good biodegradability.