Surfactant Binary Systems: Ab Initio Calculations, Preferential Solvation, and Investigation of Solvatochromic Parameters

Abstract

Solvatochromic UV−vis shifts of three probes 4-nitroaniline, 4-nitroanisol, and Reichardt's dye in binary mixtures of polyethylene glycol p-(1,1,3,3tetramethylbutyl)-phenyl ether (Triton X-100 or TX-100) with methanol, ethanol, 1propanol, and water have been investigated at 298 K. Structural and intermolecular interactions of solvatochromic probes were determined in these systems. Solvatochromic parameters, including normalized polarity (E T N ), dipolarity-polarizability (π*), hydrogenbond donor (α), and hydrogen-bond acceptor (β) abilities, were measured at a wide range of mole fraction (0 ≤ X ≤ 1) with 0.1 increment. Interestingly, a similar behavior of E T N and α is observed in alcohols/TX-100 mixtures. The E T N parameters obtained from absorbance of Reichardt's dye within various mixtures of surfactant were observed to be lower than predicted values from ideal additive behavior. A negative deviation from ideality is shown by E T N parameter in all alcohols/TX-100 mixtures, while a fluctuated behavior for other probes can be seen. The optimized geometries exhibit that the hydroxyl (−OH) group on the side chain of TX-100 significantly affects the arrangement of the selected solvents around TX-100. All binary systems show complex behavior for chosen probes. The results demonstrate that 4-nitroanisole and Reichardt's dye have stronger interactions with binary mixtures of alcohols/TX-100 systems. Synergistic solvation behavior for water/TX-100 was observed. Preferential solvation model was applied for the first time in the surfactant binary mixtures and from this model information solute−solvent and solvent−solvent interactions were interpreted. Preferential solvation (specific solute−solvent interactions) or the solvent−solvent interaction is the reason for deviation from ideal behavior of probes. As a main result, alkyl chain length of alcoholic solvents does not have impressive effects on predicted trends of solvatochromic parameters. Ab initio calculations of solvents/TX-100 mixtures demonstrate the following trend for magnitude order of interactions: water > methanol > ethanol >1-propanol. Electrostatic potential map is another confident evidence for predicted order.

Experimental and Theoretical Efforts to Identify the Microstructural Transition of Water to Acetonitrile‐Based Reverse Micelle through Binary Compositions of Polar Solvents

“…Consequently, it can be predicted that the strongest interactions are ascribed to the water/AOT complex, and the weakest interactions are attributed to the ACN/DDAB complex. Similar kind of observation was also reported earlier in order to show differential interaction between a surfactant (TX‐100) and molecular solvents such as methanol, ethanol, 1‐propanol, and water …”

Analysis of the Cybotactic Region of Two Renewable Lactone–Water Mixed-Solvent Systems that Exhibit Synergistic Kamlet–Taft Basicity

“…One reason for the lack of synergistic basicity in the MeOH–GVL system is that the cybotactic region is not fully occupied with 1–2 complex molecules, and another reason is due to the strength of the solvent–solvent interaction. Water has a higher charge separation than that of methanol; thus, the solvent–solvent interaction of water with GVL should be higher than that of methanol with GVL.…”

Correspondence between Spectral-Derived and Viscosity-Derived Local Composition in Binary Liquid Mixtures Having Specific Interactions with Preferential Solvation Theory

“…Preferential solvation (PS) theory as proposed by Rosés et al , is commonly applied with UV–vis spectroscopy that uses Kamlet–Taft (KT) solvatochromic indicators to estimate local compositions and polarity of the solutions. The PS theory has been applied to binary aqueous systems, , nonaqueous systems, − and ionic liquid–molecular solvent systems. , The PS theory is based on a solvent-exchange mechanism that occurs in the cybotactic region of a solvatochromic dye such that it allows one to estimate the local composition of (1–2) complex molecules formed between a molecule of solvent type 1 and a molecule of solvent type 2 due to specific mutual interactions that change in bulk concentration. − , In this work, local compositions determined by UV–vis spectroscopy with solvatochromic indicators (dyes) are denoted.…”