title: Interactions of an anionic surfactant with poly(oxyalkylene) copolymers in aqueous solution.
abstract: The interactions of sodium dodecyl sulfate (SDS) with poly(ethylene oxide)/poly(alkylene oxide) (E/A) block copolymers are explored in this study. With respect to the specific compositional characteristics of the copolymer, introduction of SDS can induce fundamentally different effects to the self-assembly behavior of E/A copolymer solutions. In the case of the E(18)B(10)-SDS system (E = poly(ethylene oxide) and B = poly(butylene oxide)) development of large surfactant-polymer aggregates was observed. In the case of B(20)E(610)-SDS, B(12)E(227)B(12)-SDS, E(40)B(10)E(40)-SDS, E(19)P(43)E(19)-SDS (P = poly(propylene oxide)), the formation of smaller particles compared to pure polymeric micelles points to micellar suppression induced by the ionic surfactant. This effect can be ascribed to a physical binding between the hydrophobic block of unassociated macromolecules and the non-polar tail of the surfactant. Analysis of critical micelle concentrations (cmc(*)) of polymer-surfactant aqueous solutions within the framework of regular solution theory for binary surfactants revealed negative deviations from ideal behavior for E(40)B(10)E(40)-SDS and E(19)P(43)E(19)-SDS, but positive deviations for E(18)B(10)-SDS. Ultrasonic studies performed for the E(19)P(43)E(19)-SDS system enabled the identification of three distinct regions, corresponding to three main steps of the complexation; SDS absorption to the hydrophobic backbone of polymer, development of polymer-surfactant complexes and gradual breakdown of the mixed aggregates.
authors.affiliation: National and Kapodistrian University of Athens, Department of Chemistry, Physical Chemistry Laboratory, Panepistimiopolis, 157 71 Athens, Greece. akelar@cc.uoa.gr
authors.forename: Antonios
authors.initials: A
authors.lastname: Kelarakis
authors.forename: Chiraphon
authors.initials: C
authors.lastname: Chaibundit
authors.forename: Marta J
authors.initials: MJ
authors.lastname: Krysmann
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Havredaki
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Viras
authors.forename: Ian W
authors.initials: IW
authors.lastname: Hamley