title: Dynamic phase change and local structures in IL-containing mixtures: classical MD simulations and experiments.
abstract: The dynamic phase change between a homogeneous mixture and a liquid-liquid biphase and separation of phases are explored in three-component mixtures composed of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), and water through a classical simulation method and experiment. Different experimental and theoretical tools, including density measurement, dynamic light scattering study, radial distribution, mean square displacement, an interstice model, and statistical function, are used to describe the structural modifications of the ions as a function of solution concentration. An analysis of the relation between the phase and the state of the component ions indicates that the phase separation pattern is governed by the hydrophilicity/hydrophobicity of anions. We proposed the existence of a critical point, that is, 1 : 3 : 8 for [Bmim][PF6]/[Bmim][BF4]/H2O (mole fraction). Before this critical point, obvious phase separation was seen in the mixtures. The separation phase became homogeneous with the addition of [Bmim][BF4] after this critical point. However, this homogeneous mixed solution was phase separated again upon the addition of [Bmim][PF6] or water. The existing nanostructures were present in the [Bmim][PF6]/[Bmim][BF4]/H2O mixtures, and their size abruptly decreased close to the critical point. We provided evidence of the formation of double salt ionic liquids of [Bmim][PF6]0.25[BF4]0.75·2H2O and discussed the interactions involved in these systems by examining their physicochemical properties. The ionic phase response of such three-component mixtures could be useful in various applications, especially in the dynamic control of extraction/separation processing.
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com.
authors.forename: Yang
authors.identifier: http://orcid.org/0000-0002-2510-1313
authors.initials: Y
authors.lastname: Wu
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com.
authors.forename: Xia
authors.initials: X
authors.lastname: Wang
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com.
authors.forename: Qiaozhen
authors.initials: Q
authors.lastname: Liu
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com and Beijing National Laboratory for Molecular Sciences, Key Laboratory of Colloid and Interface and Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Ma
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com.
authors.forename: Dawei
authors.identifier: http://orcid.org/0000-0002-0361-090X
authors.initials: D
authors.lastname: Fang
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Jiang
authors.affiliation: College of Chemistry, Liaoning University, Shenyang 110036, China. xiaoxma@iccas.ac.cn guanweiy@sina.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Guan