Core–Satellite Micelles by a Linear A1B1A2B2 Tetrablock Copolymer

Abstract

Block copolymers in water or compatible solvents show micelles with various shapes, such as worm-like, vesicles, and spheres. In this study, we prepared core–satellite micelles by employing a polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) linear tetrablock copolymer. When a PS-compatible solvent, for example, dimethylacetamide or diethylphthalate, is used, the PI chains form the inside core, while the PS chains become a shell as long as the volume fraction of mid PI1 chains (fPI1) is large enough (0.2) to form a loop configuration, resulting in merging into spherical cores consisting of the PI2 chains. However, at smaller fPI1 (0.08), the short mid PI1 chains cannot merge into the PI2 core and therefore exist separately as small spherical micelles, which are referred to as the “satellite” micelles. Thus, the micelles consist of large central core spheres and smaller outside satellite spherical micelles.