The dissolubility of chitosan was studied in four kinds of imidazole-based ionic liquids 1-butyl-3-methylimidazolium chloride ([BMIM]Cl)

1-butyl-3-methylimidazolium acetate ([BMIM]Ac)

1-allyl-3-methylimidazolium chloride ([AMIM]Cl) and 1-ethyl-3-methylimidazolium acetate ([EMIM] Ac) respectively.The possible dissolution mechanism of chitosan in these ionic liquids was suggested

and the chemical structures

thermal stabilities and crystalline forms of the native chitosan and regenerated chitosan from these ionic liquids were analyzed by FTIR

TGA and XRD

respectively.The results show that

chitosan can be dissolvd without derivatization by all the four kinds of ionic liquids

and the dissolubility of chitosan in these ionic liquids is mainly related to the anions of ionic liquids

but also influenced by cations of ionic liquids.The dissolving power of the two kinds of acetate ionic liquids for chitosan is stronger than that of the two kinds of chloride ionic liquids

and that of [EMIM]Ac is the strongest.15.5 wt% of chitosan dissolved in [EMIM]Ac can be achieved at 110℃.The dissolution concentration of chitosan in these ionic liquids increases

but the viscosity-average molecular weight of it decreases with the increasing of temperature and the prolongation of time.The thermal stability of the regenerated chitosan from [BMIM]Cl

[AMIM]Cl

[BMIM]-Ac and [EMIM]Ac respectively increase gradually

which is consistent with the dissolving power of these ionic liquids for chitosan

but the thermal stability of the regenerated chitosan from the four kinds of ionic liquids decreases compared with that of native chitosan.A transition of -chitosan to -chitosan may occur during the dissolving and the recovering processes.