Chitin is a natural polysaccharide abundantly present on the earth, and thus, a very important biomass resource. However, because it has high crystallinity due to strong intra- and intermolecular hydrogen bonding, its solubility and processability are poor, leading to hardly utilization. We have already reported that an ionic liquid (IL), 1-allyl-3-methylimidazolium bromide, dissolves chitin in concentrations up to 4.8 wt%, but the color of the solution is blacked, owing to the presence of bromide. Deep eutectic solvents (DESs), analogs of IL, have recently been found to act as good solvents for polysaccharides. DESs are systems formed from eutectic mixtures of hydrogen bond accepters and donors. In this study, we found that DESs composed of various imidazolium ILs and thiourea as hydrogen bond accepters and donor, respectively, dissolved chitin in 2~5 wt%. The DESs were first prepared by heating mixtures of the ILs and thiourea at 100 <sup>o</sup>C for 30 min with stirring. A predetermined amounts of chitin were then added to the DESs and the mixtures were kept at room temperature for 24 h, followed by heating at 100 <sup>o</sup>C for 24 h (Scheme 1). The dissolution state was observed by a CCD camera view. Furthermore, we found that 1-butyl-3-vinylimidazolium bromide / thiourea (1: 0.2) DES swelled 20 wt% of chitin. Functionalization of chitin using the DESs are now in progress, which will be reported in this presentation.

Dissolution and functionalization of chitin using deep eutectic solvents

2019 Fall National Meeting

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