QSPR Study On The Viscosity Of Ionic Liquids

Ionic Liquids, which emerged over the few decades, are a class of compounds which have desirable properties. Because of the properties, ionic liquids differ from traditional organic solvents and have been employed in the fields of separation, catalysis, electrochemistry, functional materials, etc., thus making it one of the hottest subjects in green chemical research. However, viscosity is a key property of ionic liquids that is worth researching in order to expand their application domains. Low viscosity ionic liquids are needed, while in some instances; for example, high viscosity ionic liquids are also favored in applications such as stationary phases for gas-liquid chromatography and when used as lubricants, a certain viscosity range is generally required. Hence,and a deep understanding of ionic liquids viscosity is necessary. In this work, with the aid of two softwares, GAUSSIAN and CODESSA, the relationship between the structure and viscosity of six types of ionic liquids and structure is understood, the microscopic nature of ionic liqids viscosity is explained, and a guide for the synthesis and applications of ionic liquids is provided. Specifically, this work is mainly concentrated on the following:1. Direct understanding based on the viscosity of ionic liquids is expanded to include the effect of cation, anion and temperature on viscosity.2. Selection and classification of ionic liquids from database which have the most viscosity data under 1atm. The selection of ionic liquids is based on least content of water and latest publication data. To this end, six types of ionic liquids comprising thirteen groups are obtained.3. Quantitative structure-property relationship (QSPR) study is performed for all the selected data sets. The thirteen correlations are obtained with R2>0.8226. From the result, it is found that the structure of cation-anion and electrostatic interaction between cation-anion play the most important role on the viscosity of ionic liquids.4. Compared with the viscosity of organic solvents, it can be seen that intermolecular hydrogen-bonding interaction and structural characteristics are the main factors affecting viscosity; for cation-fixed ionic liquids, the structure of anion and electrostatic interaction between cation-anion play the most important role on the viscosity; for anion-fixed ionic liquids, the structure of cation and electrostatic interaction between cation-anion play the most important role on the viscosity.