Aggregation properties of amphiphilic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer studied by cyclic voltammetry

The cyclic voltammetric behaviors at a platinum electrode of an amphiphilic block copolymer [poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127)] in aqueous solutions were investigated. The mechanism of the electrochemical reaction of F127 at a platinum electrode was deduced. The diffusion coefficients of different-shaped aggregates formed by F127 were determined on this basis. The first and second critical micelle concentrations, corresponding to the formation of spherical micelles and the transition of the spherical to rod-like micelles, were 3.72 x 10(-4) mol(.)L(-1) and 1.49 x 10(-3) mol(.)L(-1), respectively, which could be confirmed by the fluorescent anisotropy of pyrene in the F127 aggregates and the morphology of F127 micelles observed by freeze-fracture transmission electron microscopy.