Preparation, water absorbency, and enzyme degradability of novel chitin‐ and cellulose/chitin‐based superabsorbent hydrogels

Abstract

Superabsorbent hydrogels were prepared from chitin dissolved in lithium chloride and N-methyl-2-pyrrolidinone by esterification crosslinking with 1,2,3,4-butanetetracarboxylic dianhydride (BTCA). The absorbency of the chitin hydrogel was strongly dependent on the ratio of BTCA feed to chitin. The hydrogel prepared at the feed ratio of 5 showed the highest absorbency (345 g/g-polymer), and the hydrogel was composed of 0.65 molecules of BTCA per monomer unit of chitin. The hydrogels exhibited good biodegradability by chitinase with a maximum degradation of 91% within 7 days. This method for obtaining the chitin hydrogel was also applicable to cellulose and chitin mixtures, and 1 : 1 cellulose/chitin hybrid hydrogels could be obtained by the esterification crosslinking of a mixture with a 1 : 1 molar ratio of cellulose and chitin. The optimal BTCA feed ratio of 5 resulted in the cellulose/ chitin hydrogel with the highest water absorbency (329 g/g-polymer), and the hydrogel contained 0.65 molecules of BTCA per polysaccharide monomer unit. In addition, the hybrid hydrogels were degraded by cellulase as well as chitinase.

Removal of anionic dyes in aqueous solution by flocculation with cellulose ampholytes

“…On the other hand, flocs formed from AR13 and AB92 exhibited well-developed porous structures, with pore sizes of about 50-200 m and 10-60 m for AR13 and AB92, respectively. Such porous network structures have been frequently observed in the morphology of crosslinked polymers such as hydrogels: for example, hydrogels prepared from cellulose [45], carboxymethyl cellulose [33], chitosan [46], chitin [47], and guar gum [48], crosslinked by bifunctional crosslinking agents, showed similar porous morphologies. As described above, all polymer surfaces are positively charged at pH 3 due to the protonation of anionic carboxymethyl groups, and thus the floc formation takes place through the charge neutralization mechanism between the anionic dye and the positively charged polymer surface.…”

Hydrogels based on cellulose and chitin: fabrication, properties, and applications

“…Most esterification-type cross-linking reactions of biopolymers with carboxylic anhydrides require effective nucleophilic catalysis, and typically 4-dimethylaminopyridine (DMAP) has been used; examples include using BTCA and SA as crosslinkers. [126][127][128][129] In these reactions, DMAP initially reacts with an acyl group of the anhydride, forming a positive acylpyridinium intermediate and a negative carboxyl counterion. The polysaccharide molecules are deprotonated by the latter, and then attack the acyl group in the former to form an ester ( Fig.…”

Characterization and properties of carboxymethyl cellulose hydrogels crosslinked by polyethylene glycol

“…added to the solution to give 90% saturation. The precipitate was collected by centrifugation, 209 desalted by ultrafiltration using a Q0100 filter (Advantec Co. Ltd., Japan), and then lyophilized 210 (Kono, & Zakimi, 2013). The obtained cellulase powder was used for the biodegradation of the 211 hydrogels.…”