Expanding Alternating Spherical and Cylindrical Regions by Tailoring Binary Symmetric ABC/ABC Blends

Abstract

The self-assembly of a binary blend composed of two different symmetric ABC triblock copolymers has been investigated using self-consistent field theory in the grand canonical ensemble, aiming to expand the phase regions of alternating spherical and cylindrical phases by tailoring the molecular parameters. Our study confirms that the region of the spherical phase is expanded by the effect of bidispersity in which the long and short A-blocks (or C-blocks) form a core–shell distribution within the spherical domain to increase the spontaneous curvature. The bidispersity effect also expands the phase region of the alternating cylinders. In contrast to the spherical phase, the cylindrical region can be expanded by another effect of bidisperse B-blocks to release the high packing frustration of the low-coordinated tetragonal array of alternating A/C cylinders. With optimized parameters, the regions of both the spherical and cylindrical phases are tremendously expanded to such large volume fractions that the spheres and cylinders are remarkably deformed. Our work not only deepens the understanding on the self-assembly mechanism of ABC/ABC blends but also provides a valuable guide for the fabrication of alternating spherical and cylindrical morphologies with large volume fractions.