Dissolution, derivatization, and functionalization of chitin in ionic liquid.

In this article, a review of the researches, which endeavor concerning ionic liquids, used as media for dissolution, derivatization, and functionalization of chitin is presented. Although chitin has been noted to show poor solubility and processability, leading to mostly an unutilized biomass resource, some ionic liquids have been found to dissolve chitin. For example, an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was reported to dissolve chitin in concentrations up to 4.8 wt% and to form ion gels at higher contents of chitin. A cellulose/chitin binary ion gel was fabricated from the individually prepared cellulose/chitin solutions with ionic liquids, which was further converted into a binary film by regeneration. The binary ion gel was applied as a novel electrolyte for an electric double layer capacitor. Acetylation of chitin using acetic anhydride in AMIMBr gave chitin acetates with high degrees of substitution. The acetylation method has been extended to synthesize several chitin acylates using acyl chlorides after optimization of the conditions. The derivatization technique of chitin in AMIMBr was applied to the synthesis of a chitin macroinitiator for atom transfer radical polymerization (ATRP). Grafting of styrene by ATRP from the resulting macroinitiator was thus conducted to give chitin-graft-polystyrene.