Hydroxyl-containing ionic liquids as heat-transfer agents

Properties of Dicationic Disiloxane Ionic Liquids

“…The impossibility of crystallization of ILs based on 1-methylimidazole is explained both by the steric effect (higher mobility of imidazolium cations unsubstituted at position 2) and by the specific interaction of the hydrogen atom at position 2 of the imidazolium cation with the Tf 2 N - anion [ 26 , 27 , 28 ]. The melting point of ILs is also affected by the introduction of polar substituents into the cation [ 16 , 17 ]. Replacing the N-methyl group with a 2-methoxyethyl group in the presence of a methyl group at the position 2 of the imidazolium cation allows us to obtain ILs 10–12 that are viscous liquids at room temperature, characterized by T g = −48...−43 °C ( Table 1 ).…”

“…The introduction of polar substituents into the cation (OH-and CH 3 O-groups), which, according to our ideas, should contribute to reducing the volatility of ILs [16,17], as a result of additional intermolecular interactions with the formation of H-bonds, has a complex effect on the properties of ILs. Such a behavior is explained by the participation of polar groups in thermal decomposition processes, which, unlike the evaporation process, are intensified in the presence of the polar groups.…”

“…The introduction of polar substituents (OH groups, for example) into the cation structure or an increase in the number of ion pairs in the structures of ILs leads to a significant decrease in their volatility [16,17]. The volatility of dicationic ILs is by an order of magnitude lower than that of monocationic ones.…”

“…High thermal stability and thermal characteristics (heat capacity and heat transfer coefficient) allow them to be used as heat transfer agents in solar energy utilization systems and in heat exchange installations for heating and cooling [12][13][14]. A special feature of ionic liquids is the possibility of using them as a working fluid under dynamic vacuum conditions [15][16][17].…”

Synthesis and investigation of physico-chemical properties of dicationic ionic liquids

“…Ionic liquids (ILs) have received wide popularity in recent years in the areas of electrochemistry [1], catalytic reactions [2], organic synthesis [3], separation technology [4] and biochemistry [5]. ILs attract research interests because they possess a number of unique properties such as high thermal stability [6], no flammability [7], low vapour pressure and ease of reuse [8,9]. Moreover, the physical and chemical properties can be adjusted by altering their chemical structure of cations and anions [10,11].…”