Journal of Chemical and Engineering Data, Vol.61, No.1, 255-263, 2016
Surfactant Binary Systems: Ab Initio Calculations, Preferential Solvation, and Investigation of Solvatochromic Parameters
Solvatochromic UV-vis shifts of three probes 4-nitroaniline, 4-nitroanisol, and Reichardts dye in binary mixtures of polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (Triton X-100 or TX-100) with methanol, ethanol, 1-propanol, 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 (TT*), hydrogen-bond donor (alpha), and hydrogen-bond acceptor (beta) 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 a is observed in alcohols/TX-100 mixtures. The E-T(N) parameters obtained from absorbance of Reichardts 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 Reichardts 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.