Nanostructure in Amphiphile-Based Deep Eutectic Solvents

Iva Manasi, Ralf Schweins, Kun Ma, Karen J. Edler

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Abstract

Deep eutectic solvents (DESs) are an emerging class of modern, often “green” solvents with unique properties. Recently, a deep eutectic system based on amphiphilic surfactant N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12 & C14 sulfobetaine) and (1S)-(+)-10-camphor-sulfonic acid in the molar ratio 1:1.5 has been reported. Nanostructuring can be expected in this DES due to the nature of the components. In this work, we have investigated the native nanostructure in the DES comprising C12–C18 alkyl chain sulfobetaines with camphor sulfonic acid and how it interacts with polar and nonpolar species, water and dodecane, respectively, using small angle neutron scattering. By using contrast variation to highlight the relative position of the solvent components and additives, we can resolve the structure of the solvent and how it changes upon interaction with water and dodecane. Scattering from the neat DES shows structures corresponding to the self-assembly of sulfobetaines; the size of the structure increases as the alkyl chain length of the sulfobetaines increases. Water and dodecane interact, respectively, with the hydrophilic and hydrophobic moieties in the DES structure, primarily the sulfobetaine, thereby swelling and solvating the entire structure. The extent of the shift of the peak position, and the swelling, depend on concentration of the additive. The solution phase organization and the interaction of polar and nonpolar species as observed here, have the potential to affect the ordering of inorganic or polymeric materials grown in such solvents, paving new avenues for templating applications.
Original languageEnglish
Pages (from-to)16776-16784
Number of pages9
JournalLangmuir
Volume39
Issue number47
Early online date15 Nov 2023
DOIs
Publication statusPublished - 28 Nov 2023

Bibliographical note

I.M. acknowledges funding from EPSRC (grant number EP/S020772/1). We thank Naomi Elstone for synthesizing some of the isotopically labelled d29-SB3-14. We also acknowledge award of neutron beamtime on D22 SANS instrument at ILL under experiment number 9-10-1699 (doi: 10.5291/ILL-DATA.9-10-1699). This work benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView contains code developed with funding from the European Union’s Horizon 2020 research and innovation programme under the SINE2020 project, grant number 654000.

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