Cationic micelles in deep eutectic solvents: effects of solvent composition.

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Physical Chemistry

Background:

• Deep eutectic solvents (DES) are tunable liquid mixtures formed by hydrogen bond donors and acceptors.
• The physicochemical properties of DES, including solubility and self-assembly, can be modified by altering component ratios.
• Choline chloride (ChCl) and p-toluenesulfonic acid (pTSA) form room-temperature DES at various molar ratios (1:1, 1:2, 2:1).

Purpose of the Study:

• To investigate the solubility and self-assembly behavior of cationic surfactants (alkyltrimethyl ammonium bromides, CnTAB) in pTSA/ChCl DES.
• To understand how varying DES compositions and water content influence surfactant interactions and micelle formation.
• To explore the potential of these DES systems for controlled surfactant templating and rheology modification.

Main Methods:

• Preparation of pTSA/ChCl DES at different molar ratios (1:1, 1:2, 2:1).
• Solubility testing of CnTAB (n=12, 14, 16) in the prepared DES.
• Characterization of CnTAB micelles using small-angle neutron scattering (SANS).
• Investigation of water interactions with the surfactant-DES system.

Main Results:

• CnTAB surfactants were insoluble in the 1:2 pTSA:ChCl DES.
• CnTAB surfactants formed micelles in the 1:1 and 2:1 pTSA:ChCl DES.
• SANS data provided insights into micelle structure and the influence of DES components and water on these structures.

Conclusions:

• The composition of pTSA/ChCl DES significantly impacts CnTAB solubility and self-assembly.
• The ability to form micelles in specific DES ratios opens possibilities for controlled surfactant templating.
• These findings offer potential for tuning rheological properties in DES-based formulations.