Dissolution of α-chitin in deep eutectic solvents

Deep eutectic solvents (DESs) consisting of mixtures of choline halide (chloride/bromide)–urea, choline chloride–thiourea, chlorocholine chloride–urea and betaine hydrochloride–urea were demonstrated to be effective solvent systems for α-chitin. The dissolution of the biopolymer in the DESs was carried out by conventional heating, heating under microwave irradiation and heating assisted by ultrasonication under an inert atmosphere. Microwave and ultrasonication helped to reduce the time and temperature required for dissolution. Maximum dissolution of the biopolymer (9% w/w) was observed in the DES consisting of choline chloride–thiourea. The absence of insoluble particles in the solutions was confirmed by optical light microscope. No remarkable degradation of chitin during the dissolution process was observed upon investigations using FT-IR, XRD, 1H NMR, TGA, viscometry and rheology.