Investigating The Synthesis And Properties Of Novel Polyether Modified Quaternary Ammonium Ionic Liquids

Ionic liquids have attracted intense interest as "environmentally benign" solvents recently. However, ionic liquids reported in literature are mainly imidazolium salts, and few ionic liquids based on the quaternary ammonium salts have been reported. In this paper, a new series of ionic liquids have been prepared by introducing polyethylene glycol chain to ammonium salts, of which the structures are shown below:These salts were characterized by ¹H-NMR and ¹³C-NMR accordingly. The solid-liquid phase transition of these ionic liquids has been studied by DSC (Differential Scanning Calorimetry). The DSC results show that their melting points are all around room temperature. Increasing the polyethylene glycol chain length of the salts leads to decreasing of melting points. In addition the alkyl group and H-bond also influence their melting points. Most of these molten salts are good glass-formers. The thermogravimetric analysis shows that these salts were stable up to 280℃, and have wide liquid range. Most of these ionic liquids are immiscible with nonpolar liquids (n-heptane or toluene) and miscible with polar liquids (water or dichloromethane), the soluble behavior of these ionic liquids become similar gradually with increasing of the polyethylene glycol chain length. IL7 exhibits thermoregulated property with THF. i.e. biphasic at lower temperature and monophasic at higher temperature.