title: Competitive interactions between components in surfactant-cosurfactant-additive systems.
abstract: Complex interactions of phenol (PhOH), heptanol (HeOH) and heptanoic acid (HeOIC) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC, HeOH or HeOIC content of 0.5 mmol kg(-1), and phenol molality of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of (1)H NMR spectroscopy, titration calorimetry and solution conductimetry. The analysis of the composition-dependence of the (1)H chemical shifts assigned to selected protons in the surfactant and additive units revealed the location of PhOH both within the hydrophobic micelle core and in the vicinity of the quaternary ammonium groups, the phenol penetration being somewhat deeper in the presence of HeOIC. The phenomenon was globally more exothermic with increasing extent of PhOH solubilization and it was accompanied by a gradual decrease in the positive entropy of micellization. The solubilization was competitive for high phenol contents in the aqueous phase, with some HeOH and HeOIC units being displaced progressively towards the aqueous phase.
authors.affiliation: Institut Charles Gerhardt, Equipe Agrégats, Interfaces et Matériaux pour l'Energie, CNRS UMR 5253, Université Montpellier 2, C.C. 1502, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
authors.forename: Radhouane
authors.initials: R
authors.lastname: Chaghi
authors.forename: Louis-Charles
authors.initials: LC
authors.lastname: de Ménorval
authors.forename: Clarence
authors.initials: C
authors.lastname: Charnay
authors.forename: Jerzy
authors.initials: J
authors.lastname: Zajac
mesh_terms: D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D006538:Heptanoic Acids / Q000737:chemistry*; D019850:Heptanol / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000592:standards; D008823:Micelles; D010636:Phenols / Q000737:chemistry*; D012015:Reference Standards; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D006538:Heptanoic Acids; D008823:Micelles; D010636:Phenols; D013501:Surface-Active Agents; D019850:Heptanol; D000077286:Cetrimonium