Hierarchical Cylindrical Microdomains in an A₁BA₂C Tetrablock Terpolymer

Hierarchical cylindrical nanostructures with different diameters (or shapes) have received much attention because of potential applications to next-generation lithography or advanced optical devices. Here, we observed, via small-angle X-ray scattering and transmission electron microscopy, tetragonally and rectangularly packed hierarchical cylindrical nanostructures by tailoring the volume fraction of polystyrene mid-block in polystyrene-b-polyisoprene-b-polystyrene-b-poly(2-vinylpyridine) tetrablock terpolymer (S₁IS₂V). P2VP becomes the main cylinder, while PI forms satellite cylinders surrounding the main P2VP cylinder. When the length of S₂ block is relatively short, tetragonal arrangement of cylinders is observed. But, a rectangular arrangement of cylinders is formed for larger S₂ block. The experimentally observed hierarchical cylindrical nanostructures are in good agreement with the prediction by the self-consistent field theory.