Issue 14, 2019

Mechanisms of phase separation in temperature-responsive acidic aqueous biphasic systems

Abstract

The temperature responsive solubility of ionic liquids with ‘bulky’ polar regions, such as tributyltetradecyl phosphonium chloride ([P44414]Cl), in acidic aqueous solutions is elucidated through a combined experimental and computational approach. The temperature effect in the acidic aqueous biphasic system HCl/[P44414]Cl/H2O was characterised in the range 273 K to 373 K and was found to significantly deviate from the corresponding aqueous biphasic system with NaCl. A new transferable coarse grained MARTINI model for [P44414]Cl was developed, validated and applied to provide a molecular understanding of the experimental results. It is shown that the presence of large aliphatic moieties around the central phosphorus atoms of [P44414]Cl results in a decrease in the electrostatic repulsion between the cationic moieties, leading the [P44414]+ cation to present a behaviour conventionally associated with non-ionic surfactants. This difference in behaviour between HCl and NaCl was shown to result from the greater interaction of the hydronium cation with the micelle surface, thereby enhancing the [P44414]Cl aggregation.

Graphical abstract: Mechanisms of phase separation in temperature-responsive acidic aqueous biphasic systems

Supplementary files

Article information

Article type
Paper
Submitted
19 Dec 2018
Accepted
11 Mar 2019
First published
12 Mar 2019

Phys. Chem. Chem. Phys., 2019,21, 7462-7473

Mechanisms of phase separation in temperature-responsive acidic aqueous biphasic systems

N. Schaeffer, G. Pérez-Sánchez, H. Passos, J. R. B. Gomes, N. Papaiconomou and J. A. P. Coutinho, Phys. Chem. Chem. Phys., 2019, 21, 7462 DOI: 10.1039/C8CP07750A

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