title: Critical aggregation concentration in mixed solutions of anionic polyelectrolytes and cationic surfactants.
abstract: We have examined the polymer/surfactant interaction in mixed aqueous solutions of cationic surfactants and anionic polyelectrolytes combining various techniques: tensiometry, potentiometry with surfactant-selective electrodes, and viscosimetry. We have investigated the role of varying polymer charge density, polymer concentration, surfactant chain length, polymer backbone rigidity, and molecular weight on the critical aggregation concentration (Cac) of mixed polymer/surfactant systems. The Cac of these systems, estimated from tensiometry and potentiometry, is found to be in close agreement. Different Cac variations with polymer charge density and surfactant chain length were observed with polymers having persistence lengths either smaller or larger than surfactant micelle size, which might reflect a different type of molecular organization in the polymer/surfactant complexes. The surfactant concentration at which the viscosity starts to decrease sharply is different from the Cac and probably reflects the polymer chain shrinkage due to surfactant binding.
authors.affiliation: Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, Bâtiment 510, 91405 Orsay Cedex, France.
authors.forename: Nirmesh
authors.initials: N
authors.lastname: Jain
authors.forename: Siwar
authors.initials: S
authors.lastname: Trabelsi
authors.forename: Samuel
authors.initials: S
authors.lastname: Guillot
authors.forename: Daragh
authors.initials: D
authors.lastname: McLoughlin
authors.forename: Dominique
authors.initials: D
authors.lastname: Langevin
authors.forename: Pierre
authors.initials: P
authors.lastname: Letellier
authors.forename: Mireille
authors.initials: M
authors.lastname: Turmine