Density fluctuations in aqueous solution of ionic liquid with lower critical solution temperature: Mixture of tetrabutylphosphonium trifluoroacetate and water

Nitta, Ayako; Morita, Takeshi; Saita, Shohei; Kohno, Yuki; Ohno, Hiroyuki; Nishikawa, Keiko

doi:10.1016/j.cplett.2015.03.026

Cited by 27 publications

(17 citation statements)

References 29 publications

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“…This observation was also supported by additional experimental techniques and it was assigned to the surfactant free micellar formation by the ionic liquid that swelled in size with increasing temperature until macroscopic phase separation occurred. Aggregation behavior approaching the critical point for [P 4444 ][CF 3 COO] aqueous mixtures was also observed by density fluctuations from smallangle X-ray scattering (SAXS) 37 . However, the SAXS study did not support micelle formation i.e., structures consisting of an ordered hydrophilic shell and hydrophobic core 36 .…”

Section: Resultsmentioning

confidence: 77%

“…However, the SAXS study did not support micelle formation i.e., structures consisting of an ordered hydrophilic shell and hydrophobic core 36 . The authors concluded that the aggregates formed non-distinct 'fuzzy clusters' composed of ionic liquid and water molecules 37 . What appears consistent of IL-water LCST mixtures is the change from a more homogenous mixture (reduced density fluctuations, smaller aggregates) to a more inhomogeneous mixture upon heating up to the T c and macroscopic phase separation.…”

Section: Resultsmentioning

confidence: 99%

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Molecular insight into the lower critical solution temperature transition of aqueous alkyl phosphonium benzene sulfonates

et al. 2019

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Ionic liquid (IL)-water mixtures can exhibit a lower critical solution temperature (LCST) transition, but changes in long-range order and local molecular environment during this transition are not comprehensively understood. Here we show that in IL-H 2 O LCST mixtures, the IL forms loosely held aggregate structures that grow in size leading up to a critical temperature, whereas the aggregation of a fully miscible aqueous mixture, obtained by minor chemical modification of the anion, decreases with increasing temperature. Radial distribution functions from molecular dynamics simulations support the observation of aggregation phenomena in the IL-H 2 O mixtures. A local molecular structure of the ions is derived from multi-dimensional NMR experiments in conjunction with reported molecular dynamics simulations. In addition to considerable shifts of water's hydrogen bonding network in the fully miscible phase, by NMR we observe the anion's protons response to the intermolecular thermal environment and the intramolecular environment and find that the responses are determined by the sulfonate ionic functional group.

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Section: Resultsmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Molecular insight into the lower critical solution temperature transition of aqueous alkyl phosphonium benzene sulfonates

et al. 2019

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“…Neutron and X-ray scattering represent two of the major experimental tools to probe the structure of liquid mixtures on several different length scales [ 78 ]. The most detailed information that can be extracted from the scattered intensity is represented by the partial structure factors.…”

Section: Theoretical Computational and Experimental Methodsmentioning

confidence: 99%

“…If the interest is restricted to the mixed/demixed state of the mixture, then the

of the structure factors carries all the relevant information, and, as a further simplification, the IL/solvent sample can be seen as a pseudo-binary system, made of water and ions, without discriminating between cations and anions. Then, the relevant variables are the fluctuation

of the total number of particles, and the fluctuation

in the mutual concentration of ion and water, measured on a portion of the system that is macroscopic without including the whole sample (for which

and

vanish) [ 78 ].…”

Section: Theoretical Computational and Experimental Methodsmentioning

confidence: 99%

Thermoresponsive Ionic Liquid/Water Mixtures: From Nanostructuring to Phase Separation

et al. 2022

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The thermodynamics, structures, and applications of thermoresponsive systems, consisting primarily of water solutions of organic salts, are reviewed. The focus is on organic salts of low melting temperatures, belonging to the ionic liquid (IL) family. The thermo-responsiveness is represented by a temperature driven transition between a homogeneous liquid state and a biphasic state, comprising an IL-rich phase and a solvent-rich phase, divided by a relatively sharp interface. Demixing occurs either with decreasing temperatures, developing from an upper critical solution temperature (UCST), or, less often, with increasing temperatures, arising from a lower critical solution temperature (LCST). In the former case, the enthalpy and entropy of mixing are both positive, and enthalpy prevails at low T. In the latter case, the enthalpy and entropy of mixing are both negative, and entropy drives the demixing with increasing T. Experiments and computer simulations highlight the contiguity of these phase separations with the nanoscale inhomogeneity (nanostructuring), displayed by several ILs and IL solutions. Current applications in extraction, separation, and catalysis are briefly reviewed. Moreover, future applications in forward osmosis desalination, low-enthalpy thermal storage, and water harvesting from the atmosphere are discussed in more detail.

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“…[28][29][30] There are severalr eports on LCST-type thermomorphic behaviours of IL-water mixtures. [1] Ohno and co-workersi nvestigated LCST-type phase behaviours of many different ILs in water, [22,29,31,32] with different cloud points (T cp s) depending on the counter anions, such as 4-styrenesulfonate, [33] trifluoroacetate [31] etc. In addition to these studies, Ohno et al also described ad etailed study of a list of existing LCST-type ILs in ar ecent reviews.…”

Section: Introductionmentioning

confidence: 99%

Chemical Tuning of Zwitterionic Ionic Liquids for Variable Thermophysical Behaviours, Nanostructured Aggregates and Dual‐Stimuli Responsiveness

Biswas

Ghosh

Mandal

2018

Chemistry A European J

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The design and synthesis of a series of zwitterionic ionic liquids (ZILs) to understand the structure-property relationship towards an increase of the thermal stability, a variation of the glass transition temperature, the shape-tuning of nanostructured aggregates and the tuning of the stimuli responsiveness are demonstrated. The substitution reaction of imidazole with various aliphatic and aromatic bromides followed by the reaction of the corresponding substituted imidazoles with bromoalkyl carboxylic acids of varying spacer length produces the ZILs. In aqueous solution, a ZIL molecule either exist in its ionic liquid (substituted imidazolium bromide) form or its zwitterionic (substituted imidazolium alkyl carboxylate) form with an isoelectric point (pI) depending on the pH value of the solution. Upon changing the pH to near or above the pI, the aqueous ZIL solution undergoes transition from a transparent to a turbid phase due to the formation of insoluble hierarchical nanostructured aggregates of various morphologies, such as spheres, tripods, tetrapods, fern-like, flower-like, dendrites etc. depending on the pH of the solution and the nature of the alkyl/vinyl/aryl substituents. Upon heating the solution a phase transition occurs from turbid to transparent, exhibiting a distinct reversible upper critical solution temperature (UCST)-type cloud point (T ). It is observed that the cloud point varies with the nature of the substituent, an increase of the concentration of the ZIL as well as with changes of the pH of the solution.

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Density fluctuations in aqueous solution of ionic liquid with lower critical solution temperature: Mixture of tetrabutylphosphonium trifluoroacetate and water

Cited by 27 publications

References 29 publications

Molecular insight into the lower critical solution temperature transition of aqueous alkyl phosphonium benzene sulfonates

Molecular insight into the lower critical solution temperature transition of aqueous alkyl phosphonium benzene sulfonates

Thermoresponsive Ionic Liquid/Water Mixtures: From Nanostructuring to Phase Separation

Chemical Tuning of Zwitterionic Ionic Liquids for Variable Thermophysical Behaviours, Nanostructured Aggregates and Dual‐Stimuli Responsiveness

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