BF₃ Complexing Phosphate/Phosphonate Ionic Liquids: Synthesis, Characterization and Thermophysical Properties.

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Ionic liquids (ILs) are salts that are liquid at low temperatures, offering unique solvent properties.
• Boron trifluoride (BF3) complexation can modify IL properties, but systematic studies on phosphate/phosphonate-based systems are limited.

Purpose of the Study:

• Synthesize and characterize novel BF3 complexing phosphate/phosphonate ionic liquids.
• Investigate and compare key thermophysical properties with non-complexed analogues.
• Evaluate the potential applications of these new ILs based on their unique characteristics.

Main Methods:

• Synthesis and characterization of [Emim][X(BF3)2] ionic liquids.
• Measurement of thermophysical properties: density, viscosity, conductivity, surface tension, phase transitions, and thermal stability.
• Estimation of derived properties: thermal expansion coefficient, molecular volume, entropy, lattice energy, free volume, critical temperature, boiling temperature, and enthalpy of vaporization.

Main Results:

• Successful synthesis and characterization of four new BF3 complexing ILs.
• Demonstrated significantly lower glass transition temperatures and viscosities compared to non-complexed ILs.
• Exhibited high free volume fractions and good adherence to the Walden rule, indicating high ionicity.
• Classified as fragile liquids, with potential for low-temperature applications.

Conclusions:

• The synthesized BF3 complexing ionic liquids possess unique thermophysical properties, including extremely low glass transition temperatures and low viscosities.
• These properties make them promising candidates for applications requiring enhanced performance at low temperatures.
• The study provides valuable data for the design and application of novel ionic liquids.