Aggregation Influence of Polyethyleneglycol Organic Solvents with Ionic Liquids BMIBF4 and BMIPF6

Polyethyleneglycol (PEG, M_w = 200, 300, 400) and polyethyleneimine (PEI, M_w = 423) are used to investigate the ion‐ion interactions in liquids and physicochemical properties after the addition of PEG (or PEI) to ionic liquids 1‐butyl‐3‐methylimidazole tetrafluoroborate (BMIBF₄) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIPF₆). Nuclear magnetic resonance is used to investigate the effects of solvent content (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) and temperature (303–338 K) on the diffusion coefficient, chemical shift, and two dimensional NOESY, HOESY spectra. HOESY spectra show that a hydrogen bond forms between the alkyl hydrogen of PEG and the ¹⁹F atom of BF₄⁻ and PF₆⁻. After the addition of PEG to BMIBF₄ (or BMIPF₆), the aggregation is the dominant effect for the diffusion coefficient result. When the molecular weight and the concentration of PEG increase, the effect of coving generates larger clusters involving PEG, BMI⁺ and its counter anion. The BF₄⁻ group of the BMIBF₄/PEG system is smaller than PF₆⁻, it's easier to generate clusters in the BMIBF₄/PEG system than it is in the BMIPF₆/PEG system.