Mixed Micellar Aggregates of Nonionic and Anionic Surfactants with Short Hydrophobic Tails: A Microcalorimetric Study

• Published in: Journal of colloid and interface science 2002-05, Vol.249 (2), p.481-488
• Main Authors: Ortona, Ornella, D'Errico, Gerardino, Vitagliano, Vincenzo, Costantino, Lucia
• Format: Article
• Language: English
• Subjects: calorimetry; Chemistry; Exact sciences and technology; General and physical chemistry; ionic surfactant; mixed micelles; nonionic surfactant; Surface physical chemistry; Surface-active agents: properties
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.2002.8280

Apparent molar relative enthalpies were measured for the nonionic ethoxylated surfactant CH3–(CH2)5–(OCH2–CH2)5OH (C6E5) in aqueous solution at constant molality of the ionic surfactant CH3–(CH2)5–SO–3Na+(C6SNa) at 25°C. The experimental data obtained by a stepwise dilution process allowed evaluation of the C6E5 first interaction parameter at several constant molalities of C6SNa. The C6E5 critical micelle composition as a function of the C6SNa molality was also estimated. The experimental calorimetric data, together with the mixed micelles composition computed in the past by some of us [Ciccarelli et al., Langmuir14, 7130 (1998)], allowed computation of the ΔhMic of micellization. The experimental data are compared to those predicted by the ideal solution model and regular solution model of mixed micellization. From a calorimetric study performed on the water–hexanol–C6SNa and water–penthaethylene glycol–C6SNa model systems, it can be argued that the interactions among the hydrophilic heads in the C6E5–C6SNa mixed micelles prevail on the contribution of the hydrophobic tails in ruling the enthalpic properties of the system.