As expected, the viscosity decreases slightly with the increase of temperature. The higher viscosity of GBOC6-BF4, compared to this Muscimol of GBOC6-Dca is ascribed to the intermolecular friction generated by the anion. The intermolecular friction generated by rod-shaped Dca− anion is thought to be smaller than that of spherical BF4− anion, resulting in their different viscosities . Similar interpretation can be given to explain the difference of viscosity between GBOC12-Dca and GBOC12-Lac. The determined viscosities of GBOC12-Lac, GBOC14-Lac and GBOC16-Lac at 90 °C are 30.7 cP, 132.3 cP and 195.0 cP, respectively. In accordance with previous works , , ,  and , the lengthening of the alkyl chain leads to an increase of viscosity. For the series of ILs with lactate anions, the increase could be attributed to the interactions of Van der Waals between the alkyl chains .
The data of physical properties on ionic liquids are essential for both theoretical research and industrial applications. In this work, new “green” ionic liquids containing an esterified Glycine-Betaine with different alkyl chains and different inorganic and organic anions have been synthesized. Their physicochemical properties such as glass transition and decomposition temperature, viscosity, and melting point have been determined in order to study the relationship between structure and properties. In all cases, the lengthening of the alkyl chain enhances the thermal stability of these ionic liquids. The thermal and viscosity properties of these ILs with the inorganic anions are totally different compared to those with organic anions.