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

Abstract

Abstract 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 (BMIBF 4 ) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIPF 6 ). 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 19 F atom of BF 4 − and PF 6 − . After the addition of PEG to BMIBF 4 (or BMIPF 6 ), 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 BF 4 − group of the BMIBF 4 /PEG system is smaller than PF 6 − , it's easier to generate clusters in the BMIBF 4 /PEG system than it is in the BMIPF 6 /PEG system.