September 26, 2019
Journal Article

Two Coexisting Liquid Phases in Switchable Ionic Liquids

Musahid Ahmed
Tyler Troy
Xiao Sui
Yufan Zhou
Satish Nune
Juan Yao
David Lao
Xiang Ma
David Heldebrant
Zihua Zhu
Xiao-Ying Yu
In situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) coupled with a vacuum compatible microfluidic reactor, System for Analysis at Liquid Vacuum Interface (SALVI), has enabled the first spatial mapping of the switchable ionic liquids (SWILs) derived from 1,8-diazabicycloundec-7-ene (DBU) and 1-hexanol. As predicted by molecular dynamic simulations, our molecular imaging results confirmed a dynamic heterogeneous molecular structure with ionic regions (high CO2 concentration) coexisting with non-ionic regions (no CO2) where stoichiometry would indicate otherwise. Chemical speciation was also found to be more complex than initially thought, with spectral principal component analysis identifying dimers that ultimately highlight a highly complex molecular structure unique to SWILs. The spatial chemical mapping enabled by ToF-SIMS and SALVI advances the understanding of how the heterogeneous molecular structure impacts the dynamic physical and thermodynamic properties or SWILs.

Revised: September 26, 2019 | Published: August 30, 2017

Yao J., D. Lao, X. Sui, Y. Zhou, S.K. Nune, X. Ma, and T. Troy, et al. 2017. "Two Coexisting Liquid Phases in Switchable Ionic Liquids." Physical Chemistry Chemical Physics. PCCP 19, no. 34:22627-22623. PNNL-SA-122167. doi:10.1039/C7CP03754F