Unconventional microdomains of block copolymers

Abstract

Block copolymers (BCPs) have attracted significant interest due to their ability to form various nanostructures, including lamellae, cylinders, gyroids, and spheres. But these nanostructures are only observed for limited range of the volume fraction of one block. Namely, lamellar microdomains are observed for symmetric volume fraction, whereas spherical microdomains are found for highly asymmetric volume fraction. To increase the potential applications of these nanostructures for next‐generation lithography, advanced optical materials, and high‐performance membranes, one should have these nanostructures beyond the limitation of the volume fraction. During the past decades, many directions, such as blends of two BCPs, design of complex chain architecture of BCP and introduction of favorable interactions between block components, have been suggested to greatly change the phase boundaries of conventional nanostructures. In this review, we focus on unconventional nanostructures, such as highly asymmetric lamellae, inverted cylinders and gyroids, and spherical microdomains at nearly symmetric volume fraction.

Stabilizing DG, DD, and DP Bicontinuous Network Phases in Pure AB-Type Block Copolymers beyond Relieving Packing Frustration

“…The fundamental idea originates from a recent work by Qiang et al., where a considerable stability region of the DP phase is predicted in the phase diagram of a purposely designed dendron-like AB-type multiblock copolymer with A-blocks forming a cone shape . Since the cone shape of the A-blocks accommodates the increasing volume along the radial direction for a given AB-interfacial curvature, the effect of spontaneous curvature is largely enhanced, enlarging the tendency of curving interfaces toward A domains. , As a result, an extremely expanded spherical phase region is achieved, at the corner of a large volume fraction and a high χN (χ: Flory–Huggins parameter; N : total number of statistical segments on each copolymer) of which the DP phase rather than DG or DD surprisingly appears. From the point of view of sphere, the DP phase resembles the body-centered-cubic (BCC) phase with connected spheres due to the large volume fraction.…”

High-Density Packing of Spherical Microdomains from A(AB3)3 Dendron-like Miktoarm Star Copolymer

“…Block copolymers (BCPs) can be self-assembled into various nanostructures, such as spheres, cylinders, gyroids, and lamellae, depending on the volume fraction ( f ), the degree of polymerization ( N ), and the Flory–Huggins interaction parameter (χ). − These nanostructures can be used for next-generation lithography, ultrahigh-density memory devices, high-flux membranes, and advanced optical devices. − Particularly, spherical nanostructures have received great attention because they can be regarded as artificial atoms that help to understand the formation of various crystalline orders. − However, the expansion of the stable region of the spherical phases remains a great challenge. Conventionally, A spheres in an AB diblock copolymer are found when f A is far below 0.5 (say, f A < 0.18).…”