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

authors	Schaeffer, N; Perez-Sanchez, G; Passos, H; Gomes, JRB; Papaiconomou, N; Coutinho, JAP
nationality	International
journal	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
keywords	COARSE-GRAINED MODEL; IONIC-LIQUID; WATER; SURFACTANTS; COACERVATION; TRANSITION; EXTRACTION; MIXTURES; MICELLES; BEHAVIOR
abstract	The temperature responsive solubility of ionic liquids with bulky' polar regions, such as tributyltetradecyl phosphonium chloride ([P-44414]Cl), in acidic aqueous solutions is elucidated through a combined experimental and computational approach. The temperature effect in the acidic aqueous biphasic system HCl/[P-44414]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 [P-44414]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 [P-44414]Cl results in a decrease in the electrostatic repulsion between the cationic moieties, leading the [P-44414](+) 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 [P-44414]Cl aggregation.
publisher	ROYAL SOC CHEMISTRY
issn	1463-9076
isbn	1463-9084
year published	2019
volume	21
issue	14
beginning page	7462
ending page	7473
digital object identifier (doi)	10.1039/c8cp07750a
web of science category	Chemistry, Physical; Physics, Atomic, Molecular & Chemical
subject category	Chemistry; Physics
unique article identifier	WOS:000464580600021