Time-resolved fluorescence anisotropy measurements on fluorescently tagged amphiphilic micelles

Block copolymers of polystyrene-block-poly)methacrylic acid) form multimolecular micelles in mixtures of 1,4-dioxane with a surplus of methanol at ambient temperatures. Micelles consist of compact polystyrene cores surrounded by outer shells formed by poly(methacrylic acid) and are in a reversible equilibrium with nonmicellized copolymer chains (unimers). A series of light scattering, ultracentrifugation, and fluorimetric measurements was performed on micellizing systems of end-tagged copolymers. Complex time-resolved fluorescence anisotropy decays may be explained by a distribution of fluorophores in two microenvironments, i.e., in compact polystyrene micellar cores and in unimer coils.