High‐pressure infrared spectroscopy of ionic liquids mixed with Tween 80

Abstract

In this study, the possibility of using Tween 80 to disturb the microstructures of 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM]BF4) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM]PF6) was investigated under high pressures. The imidazolioum CH absorptions of pure ionic liquids (ILs) are significantly blue‐shifted under high pressures. However, mild changes in imidazolioum CH stretching frequencies were observed for IL/Tween 80 mixtures. Tween 80 may hinder cations of ILs to form network structures with anions under high pressures via pressure‐enhanced cation‐Tween 80 interactions. Based on the experimental results, Tween 80‐[BMIM]PF6 interactions are more effective in disturbing the local structure of imidazolium CH than Tween 80‐[BMIM]BF4 interactions.