Origin of low melting point of ionic liquids: dominant role of entropy

Abstract

Ionic liquids (ILs) are salts with an extremely low melting point. Substantial efforts have been made to address their low melting point from the enthalpic standpoint (i.e. interionic interactions). However,...

Insights into structure–property relationships in ionic liquids using cyclic perfluoroalkylsulfonylimides

“…The correlation between ion rigidity/flexibility and low melting points has been rationalized through the entropy of the liquid phase. 22 A higher number of available conformers in the liquid phase typically results in an increase of entropy leading to lower melting temperatures of the IL. 23 The influence of conformational flexibility on the thermal properties is reflected by the phase transitions of the ILs presented in this study ( Table 3 ).…”

“…15,18,19,125 and conformational exibility. 4,[22][23][24] For all three different types of ILs with the cations, [EMIm] + , [BMIm] + and [BMPL] + , the respective TFSI-IL possesses the lowest dynamic viscosity (Table 5 and Fig. 11).…”

“…20 A further properties determining factor is the conformational exibility of the ions as a higher number of conformers increases the entropy of the liquid. 4,[21][22][23][24] So, the introduction of exible alkyl chains is a common strategy for the design of low-melting ILs, e.g. in 1-alkyl-3methylimidazolium ions.…”

Effect of cation alkyl chain length on 3-sulfopropylmethacrylate-based draw solutes having lower critical solution temperature

“…ILs, which are organic salts that have a melting point of less than 100 °C can dissociate in water-forming ions, leading to osmolality. 38,39 ILs also have attractive characteristics including negligible volatility, high ion density and ionic conductivity, tunable polarity, basicity, and acidity. [40][41][42][43] The most crucial feature of ILs is the ability of their physicochemical properties to be tuned by modication of their alkyl chain length and an ionic precursor according to application requirements, such as electrochemistry, 44 catalysis, 45,46 and extraction.…”

Anion Effect on Forward Osmosis Performance of Tetrabutylphosphonium-Based Draw Solute Having a Lower Critical Solution Temperature

“…Various thermo-responsive draw solutes have been explored, which include hydrogels [ 32 , 33 ], homopolymers [ 18 , 34 ], oligomers [ 20 ], and copolymers [ 21 ]. Recently, thermo-responsive ILs have been considered promising draw solutes because ILs can dissociate in water, leading to osmolality [ 35 , 36 ]. ILs have several distinct characteristics, such as high ionic conductivity, thermal stability, tunable polarity, and negligible volatility [ 37 , 38 , 39 , 40 ].…”