title: Interactions of univalent counterions with headgroups of monomers and dimers of an anionic surfactant.
abstract: Specific ion effects in solution are related to the hydrated ion size and ion hydration, electrostatic interactions, dispersion forces, ion effects on water structure, and ion modification of surface tension. In this study, we tried to identify which factor determines the ion specificity observed. The preference and energy of metal cations binding with the headgroups of dodecylsulfate (DS) monomers and dimers were determined by mass spectrometry. In the gas phase, cation binding to DS dimer headgroups depends strongly on the cation radius. On the other hand, the interactions between DS monomer headgroups and chaotropic ions depend on the cation polarizability, and the binding of kosmotropic cations to DS monomer headgroups strongly depends on the Gibbs free energies of ion hydration. DS dimers are related to surfactants having doubly charged headgroups, and DS monomers are related to surfactants with singly charged headgroups. Our spectrometric study of the strength of counterion binding to free monomers of a surfactant provides insight into surfactant-counterion interactions at micellar interfaces in bulk solution.
authors.affiliation: Department of Physical Chemistry, Adam Mickiewicz University, Umultowska 89 b, 61-614 Poznań, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Jakubowska
mesh_terms: D000838:Anions / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000838:Anions; D013501:Surface-Active Agents