Insight into the structure-function relationships of the solubility of chitin/chitosan in natural deep eutectic solvents

Recently, the development of solution processing of chitin/chitosan in natural deep eutectic solvents (NADESs) is one of the most promising strategies for handling insoluble biopolymers. A facile and efficient approach including choline chloride-based and betaine-based NADESs, were designed as solvents for chitin/chitosan with various degree of deacetylation (DD). The maximum solubility of chitin/chitosan (10.2 g/100 g) was obtained in NADESs composed of choline chloride-lactic acid (ChLa). The relationships between the solubility, crystallinity index (CrI), and DD of the dissolved chitin/chitosan with different pH values of NADESs were discussed, and the results indicated that DD of chitin/chitosan dominated its solubility. Furthermore, mechanistic analysis showed that the hydrogen-bonding interactions contained NH⋯OH or OH⋯OH between chitin and NADESs was the possible reason for better solubility of chitin in ChLa. The NADESs-chitin processing platform in this text reveals the potential of NADESs for the environmentally-aware research and developing chitin-based industrial processes and products.