Effect of Pyrrolidinium Formate Ionic Liquid on Micellization of Direct and Reverse Pluronics in Aqueous Solutions

Abstract

The behavior of direct and reverse Pluronic, copolymer nonionic surfactants, poly(ethylene oxide) PEO, and poly(propylene oxide) PPO copolymers, in aqueous solution and in the pyrrolidinium formate ([pyrr][F]) ionic liquid, was investigated using Fourier transform infrared spectroscopy (FTIR spectroscopy). The study was performed for a fixed Pluronic concentration at room temperature. We showed that in aqueous solution, the spectra associated with the direct and reverse Pluronics are similar irrespective of the difference in length of the various PPO and PEO blocks, their positions and the PPO:PEO ratio. The study of those same Pluronics dissolved in a pure pyrrolidinium formate solution showed that the Pluronic types were soluble and that the micellization process can take place at room temperature. The interaction between the Pluronic 10R5 aqueous solutions and the [pyrr][F] for various ionic liquid volumes is reported.