Micellar Shape Change and Internal Segregation Induced by Chemical Modification of a Tryptych Block Copolymer Surfactant

We report the detailed characterization of micelles formed by two nonionic, amphiphilic ABC triblock copolymers. Poly(ethylene oxide)-<i>b</i>-poly(styrene)-<i>b</i>-1,2-poly(butadiene) (PEO-<i>b</i>-PS-<i>b</i>-PB) triblock copolymer “OSB” forms core−corona spherical micelles in aqueous solution, and the two hydrophobic blocks S and B are mixed homogeneously within the micelle core. PEO-<i>b</i>-PS-<i>b</i>-PB:C<sub>6</sub>F<sub>13</sub>I triblock copolymer “OSF” was prepared by selective fluorination of the B block in OSB with <i>n</i>-perfluorohexyl iodide. Fluorination of the B block induces internal segregation into an inner F core and an intermediate S shell. Furthermore, the strong incompatibility that results from fluorination drives a shape change into an oblate ellipsoid. These micellar morphologies are confirmed by combined light, neutron, and X-ray scattering measurements, as well as TEM imaging.