Hosein Bidgoli, Akram Zamani, Mohammad Taherzadeh. Effect of carboxymethylation conditions on water binding capacity of chitosan-based superabsorbents. Carbohydrate research 2010; 345:2683-2689.

Superabsorbent polymers (SAPs) were prepared from carboxymethyl chitosan (CMCS) cross-linked to a gel,
concentrated by partial dehydration in a rotary evaporator (at 70, 85, and 100 °C), frozen at -5, -20, and
-196 °C, and then freeze dried. A 0.9% aqueous solution of CMCS was gelled by addition of glutaraldehyde
and partially dehydrated to 1.3-16.8% dry matter (DM) before freeze drying. The water binding capacity
(WBC) of the products was up to 171 g/g of superabsorbent. The best results were obtained when 32-81%
of the water in the gel was removed in the evaporator at 85-100 °C, and the concentrated gel (1.3-4.7%
DM) was frozen in liquid nitrogen at -196 °C before freeze drying. On average, these SAPs, according to
SEM micrographs, had a porous sponge-like structure and absorbed 35 and 32 g/g of saline and urine solutions
after 10 min exposure, respectively. The corresponding WBC of two commercial polyacrylate-based SAPs
was 34-57 g/g for saline and 30-37 g/g for urine solutions.