Extended dissolution studies of cellulose in imidazolium based ionic liquids

Ionic liquids (ILs) have become advantageous solvents for the dissolution and homogeneous processing of cellulose in recent years. However, despite significant efforts, only a few ILs are known for their capability to efficiently dissolve cellulose. In order to overcome this limitation, we screened a wide range of potentially suitable ILs. From our studies, some remarkable results were obtained, for example, an odd-even effect was found for different alkyl side-chain lengths of the imidazolium chlorides which could not be observed for the bromides. Furthermore, 1-ethyl-3-methylimidazolium diethyl phosphate was found to be best suitable for the dissolution of cellulose; dissolution under microwave irradiation resulted in almost no color change. No degradation of cellulose could be observed. In addition, 1-ethyl-3-methylimidazolium diethyl phosphate has a low melting point which makes the viscosity of the cellulose solution lower and, thus, easier to handle.