Identifying the Lower Critical Solution Temperature with Viscosity

Ionic liquids (ILs) are organic salts with very low melting points (< 100°C). The melting temperature will depend on the specific anion-cation combination with some salts existing in a fluid state even at room temperature or below. ILs have several desirable properties such as low volatility, both chemical and thermal stability, and high charge density. As a result, they can function as solvents, electrolytes, or functional materials when modified (Kohno and Ohno, 2012).

The miscibility of an IL with water is an important consideration when tailoring the anion-cation pair for certain applications. Since accurate determination of the LCST is important when establishing process parameters, experimental techniques such as UV-vis spectroscopy and differential scanning calorimetry (DSC) are often used to quantify the LCST.

In this application note, we explore the ability of temperature dependent viscosity measurements to identify the phase transition and compare the results to those presented in the literature (Haddad et al., 2021).

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