Micellization and surface properties of Triton X 100 in aqueous solution of short-chain alcohols

Abstract

This study investigates the micellization and surface properties of nonionic surfactant Triton X-100 (TX100) in binary water-alcohol mixtures containing methanol (MeOH), ethanol (EtOH), and 1-propanol (1-PrOH) at 293.15 K. Binary mixtures with alcohol volume fractions ($\mathrm{VF}$) of 0.10, 0.20, 0.30, 0.40 and 0.50 were prepared. Surface tension measurements were carried out to determine the critical micelle concentration ($\mathrm{CMC}$) and surface properties, including maximum surface excess concentration (${\Gamma }_{\max }$), minimum area per molecule ($A_{\min }$), surface pressure (${\pi }_{\mathrm{cmc}}$) Gibbs free energy of adsorption ($\Delta G_{\mathrm{ads}}^o$) and Gibbs free energy of micellization ($\Delta G_m^o$). The results show that alcohol addition significantly influences micellization and interfacial behavior. $\mathrm{CMC}$ increased with increasing $\mathrm{VF}$ of alcohol, reflecting reduced hydrophobic interactions and a decline in polarity of medium. Above 0.30 $\mathrm{VF}$ of EtOH and 0.20 $\mathrm{VF}$ of 1-PrOH, formation of micelle ceases, indicating suppressed micellization due to extensive disturbance of water's hydrogen-bonding network, reduced cohesive energy density ($\mathrm{CED}$), and dominance of alcohol-surfactant interactions. Surface properties reveal a decline in ${\Gamma }_{\max }$ and ${\pi }_{\mathrm{cmc}}$, alongside an increase in $A_{\min }$ conforming reduce adsorption efficiency. Thermodynamic analysis shows that both $\Delta G_m^o$ and $\Delta G_{\mathrm{ads}}^o$ becomes less negative with increasing alcohol content, indicating unfavorable micelle formation and adsorption. These findings suggest that solvent parameters, such as the Gordon Parameter ($\mathrm{GP}$) and $\mathrm{CED}$ play a critical role in modulating surfactant behavior in mixed solvent systems.