title: Salt effect on the interactions between gemini surfactant and oppositely charged polyelectrolyte in aqueous solution.
abstract: The effect of alkali halides (NaBr, NaCl, KCl) on the interactions between the cationic gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and the anionic polyelectrolyte sodium polyacrylate (NaPAA) in aqueous solution has been investigated by fluorescence emission spectroscopy, UV transmittance, zeta potential, and transmission electron microscopy (TEM). With increased addition of NaBr, a counterbalancing salt effect on the critical aggregation concentration (CAC) is observed. At low concentrations, NaBr facilitates the formation of micelle-like structures between surfactant and polyelectrolyte and results in a smaller CAC. At high concentrations, NaBr screens the electrostatic attraction between surfactant and polyelectrolyte and leads to a larger CAC. Upon the formation of micelle-like structures at high surfactant concentrations, the addition of NaBr is favorable for larger aggregates. The microstructure detected by TEM show that a global structure is generally formed in the presence of NaBr. The interactions also depend on ion species. Compared to NaBr, the addition of NaCl or KCl yields a smaller CAC.
authors.affiliation: Lab for Advanced Materials and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Pi
authors.forename: Yazhuo
authors.initials: Y
authors.lastname: Shang
authors.forename: Honglai
authors.initials: H
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Hu
authors.forename: Jianwen
authors.initials: J
authors.lastname: Jiang