title: Aqueous mixtures of di-n-decyldimethylammonium chloride/polyoxyethylene alkyl ether: dramatic influence of tail/tail and head/head interactions on co-micellization and biocidal activity.
abstract: Mixed aggregate formation and synergistic interactions of binary surfactant mixtures of di-n-decyldimethylammonium chloride, [DiC(10)][Cl], with polyoxyethylene alkyl ethers, C(i)E(j) (i=10, 12, j=4, 6, 8), have been investigated for various [DiC(10)][Cl]/C(i)E(j) ratios. The critical aggregation concentration of the binary mixtures has been determined by tensiometry, and the aggregate characteristics (i.e., size and composition, free ammonium concentration) have been estimated using the pulsed field gradient NMR spectroscopy and a [DiC(10)]-selective electrode. Diffusion coefficient measurements of micelles confirmed the synergistic interaction between the surfactants. It is thus shown that the formation of surface monolayers and mixed aggregates from [DiC(10)][Cl]/C(10)E(j) mixtures is driven by both tail/tail and head/head interactions, whereas [DiC(10)][Cl]/C(12)E(j) co-aggregation is mainly driven by tail/tail interactions. As a consequence, the co-aggregation phenomenon notably influences the biocidal activity of [DiC(10)][Cl] on the Candida albicans fungi. In the presence of C(12)E(j), the biocidal activity of the ammonium salt is inhibited due to the trapping of the cationic surfactants in the mixed aggregates, whereas in the presence of C(10)E(j), the biocidal activity of the surfactant mixture is maintained. The mode of action is also confirmed by a faster increase in the zeta potential of a C. albicans suspension in the presence of [DiC(10)][Cl]/C(10)E(8) than in the presence of [DiC(10)][Cl]/C(12)E(8). Therefore, a judicious adjustment of the alkyl (i) and polyoxyethylene (j) chain lengths of C(i)E(j) avoids its antagonistic effect on the biocidal activity of [DiC(10)][Cl].
authors.affiliation: Laboratoires Anios, Pavé du Moulin, F-59260 Hellemmes Lille, France.
authors.forename: Gaétan
authors.initials: G
authors.lastname: Rauwel
authors.forename: Loïc
authors.initials: L
authors.lastname: Leclercq
authors.forename: Jacques
authors.initials: J
authors.lastname: Criquelion
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Aubry
authors.forename: Véronique
authors.initials: V
authors.lastname: Nardello-Rataj
mesh_terms: D002176:Candida albicans / Q000187:drug effects* / Q000254:growth & development; D004058:Diffusion; D004202:Disinfectants / Q000737:chemistry* / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry* / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D004202:Disinfectants; D008823:Micelles; D000644:Quaternary Ammonium Compounds; C495681:Sanonic SS-90; D013501:Surface-Active Agents; D014867:Water; D011092:Polyethylene Glycols; C027118:didecyldimethylammonium