Interactions between Nonionic Surfactant Micelles Introduced by a Telechelic Polymer. A Small Angle Neutron Scattering Study

The nonionic surfactant hexa(ethylene glycol) mono- n -dodecyl ether (C12EO6) self-assembles in aqueous solutions to form small globular micelles. Progressive substitution of C12EO6 by a telechelic polymer (a water soluble poly(ethylene oxide) (PEO) chain grafted at both extremities with hydrophobic C 12 H 25 chains (PEO-2m)) is shown to preserve the initial C12 hydrophobic cores, at least up to 10 polymers per hydrophobic core, but to introduce additional interactions between the micelles. At low micellar concentrations (∼ <0.03 M) these interactions are attractive, leading to a phase separation even with a minute substitution of C12EO6 by the polymer while at higher concentrations even a minute substitution leads to an effective repulsive interaction. These observations are discussed in terms of a competition between bridging and decoration of the micelles.