Influence of amino acid-based deep eutectic solvents on the micellization behavior of Triton X-100: A comparative spectroscopic study

Abstract

Deep eutectic solvents have found themselves as a flexible green media that has broad hydrogen-bond networks and adjustable polarity that can substantially alter interfacial and self-assembly events. This work contains a systematic study of the micellization principle of the non-ionic surfactant Triton X-100 in aqueous media under the influence of three novel amino acid-based deep eutectic solvents (DESs) consisting of choline chloride as a hydrogen-bond acceptor and various amino acids as hydrogen-bond donors. The multi-technique experimental method of surface tension measurements, fluorescence spectroscopy, UV-visible spectroscopy, viscosity, and Fourier-transform infrared (FTIR) spectroscopy was also used to investigate the effect of DES composition and concentration (5 and 10 wt%) on critical micelle concentration (CMC), interfacial parameters, micellar microenvironment, and molecular interactions. The surface tension measurements indicate progressive reduction of the CMC of Triton X-100 with the addition of DESs, which evidences the increased self-assembly of the surfactant. The intensity of CMC decrease is highly dependent on the type of amino acid, as this indicates variations in hydrogen-bonding aptitude, polarity, and solvation influences. Fluorescence analysis with pyrene as a probe indicates an unanimously varied ratio of I1/I3, which supports the alteration of micellar micropolarity and supports the existence of the more hydrophobic microenvironment in the presence of DES. Pre-micellar and micellar interactions are further supported by UV-visible spectroscopy, which gives concentration-dependent spectral changes, and viscosity measurements, which give information on structural and rheological changes induced by the incorporation of DES. The FTIR spectral analysis indicates that characteristic vibrational bands can be distinguishably shifted, indicating the presence of a particular interaction of hydrogen bonds between Triton X-100, water, and DES components, which is the basis of changes in the behavior of micellization.

The paper provides a comparative, mechanistic, and thermodynamic reason for how the amino acid structure influences hydrogen bonding, interfacial adsorption, micellar microenvironment, and spontaneity of aggregation. The results demonstrate their irrevocable correlations of structure and properties and demonstrate how amino acid-based DESs can be selected rationally to optimize the micellar systems to facilitate their further application in sustainable colloidal and formulation chemistry.