Uniform Toroidal Micelles via the Solution Self-Assembly of Block Copolymer–Homopolymer Blends Using a “Frustrated Crystallization” Approach

Toroidal nanostructures are of growing importance due to their unique geometry and potential utility in materials fabrication. Although a variety of amphiphilic block copolymers has been shown to self-assemble into toroidal micelles, the conventional methods used are often very slow with little control over the size of the resulting nanostructures. Here, we report a rapid and efficient synthetic route to prepare toroidal micelles of near uniform diameter through the cooperative coassembly of amorphous blends of polyferrocenylsilane block copolymer and homopolymer, where the degree of polymerization of the core-forming metalloblock in the former is greater than for the latter. The self-assembly process is accomplished within a few minutes, and the ring size of the toroids can be varied between 30 and 90 nm by adjusting the mass ratio of the block copolymer and homopolymer. The kinetic stability of the resulting toroidal micelles can be enhanced by frustrating core crystallization through solvent modulation and the toroids can also be readily used as templates to fabricate circular arrays of metal nanoparticles.