Investigating micelle formation in systems with benzethonium chloride and n-lauroyl sarcosine sodium salt: The impact of thermal effects and ethyl lactate concentration using volumetric, statistical, acoustic, and molecular dynamic methods

Abstract

Surface active agents (SAAs) are versatile molecules that possess the ability to serve as multifunctional ingredients in a wide range of consumer products across various industrial sectors. These molecules can act as wetting and dispersion agents, emulsifiers, foaming and anti-foaming agents, lubricants, and more. The objective of this study was to evaluate the effect of temperature, and ethyl lactate concentration on micelle formation in systems containing benzethonium chloride (BC) and N-lauroyl sarcosine sodium salt (NLSS). The experimental measurements were conducted at three equidistant temperatures i.e., 298.15 K to 318.15 K and pressure, P=0.1 MPa. Several volumetric as well as compressibility parameters including apparent molar properties (Vϕ,Kϕ,S), partial molar properties (Vϕ°,Kϕ,S°), transport properties (ΔtrVϕ°,ΔtrKϕ,S°), hydration number, etc. have been evaluated. A Bayesian two-factor design with uninformative priors was used to analyze the values of Vϕ°,and Kϕ,S°. It was possible to determine that the temperature factors, and the ethyl lactate (EL) addition significantly influence the results for Vϕ° while for Kϕ,S°it is not appreciable at 5 and 10 % in EL concentration when BC and NLSS systems is compared. The simulations of the micellization process show the impact of temperature, particularly in the presence of ethyl lactate, is evident in the structural and dynamic changes observed in the micelles. Specifically, as the temperature rises from 298.15 K to 318.15 K, the self-assembly process becomes more spontaneous and accelerated, leading to larger and more spherical micelles. These alterations in micelle size, shape, and orientation enhance their capacity to effectively solubilize hydrophobic substances. The computational simulations demonstrated that BC molecules exhibit spontaneous aggregation at the interface of polar-nonpolar systems, resulting in the formation of a monolayer. In this monolayer, the heads of the molecules are oriented towards the polar phase, while the hydrophobic tails are in the nonpolar phase. Similarly, the NLSS system exhibits a continuous and gradual process of self-organization over a period of 120 ns, where NLSS molecules naturally come together to create a single layer arrangement at the zigzag-shaped boundary.