Micellization and surface properties of Triton X 100 in aqueous solution of short-chain alcohols
Sujit Kumar Shah, Rojer M. Leblanc, Ajaya Bhattarai
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 ( 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 ( CMC ) and surface properties, including maximum surface excess concentration ( Γ max ), minimum area per molecule ( A min ), surface pressure ( π cmc ) Gibbs free energy of adsorption ( Δ G ads o ) and Gibbs free energy of micellization ( Δ G m o ). The results show that alcohol addition significantly influences micellization and interfacial behavior. CMC increased with increasing VF of alcohol, reflecting reduced hydrophobic interactions and a decline in polarity of medium. Above 0.30 VF of EtOH and 0.20 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 ( CED ), and dominance of alcohol-surfactant interactions. Surface properties reveal a decline in Γ max and π cmc , alongside an increase in A min conforming reduce adsorption efficiency. Thermodynamic analysis shows that both Δ G m o and Δ G 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 ( GP ) and CED play a critical role in modulating surfactant behavior in mixed solvent systems.