Process-Directed Self-Assembly of the Frank-Kasper A15 Structure in Linear, Conformationally Symmetric Block...

Area of Science:

• Materials Science
• Polymer Chemistry
• Self-Assembly

Background:

• Complex self-assembled phases in block copolymers often exhibit long equilibration times and competing structures.
• Reproducibly directing the structure evolution of these complex phases is essential for material design.

Purpose of the Study:

• To design a deterministic process for transforming the double-gyroid (DG) phase into a metastable A15 structure.
• To overcome challenges associated with long equilibration times and competing structures in block copolymer self-assembly.

Main Methods:

• Utilized general symmetry considerations to design a transformation pathway.
• Irreversibly switched a conformationally symmetric ABB' diblock copolymer into an ABA' triblock copolymer.
• Employed dynamic self-consistent field theory and particle-based simulations for validation.

Main Results:

• Successfully transformed the DG phase into a metastable Frank-Kasper A15 structure.
• Leveraged nonmonotonic segregation time evolution to partition the DG unit cell into 8 A15 units.
• Demonstrated the robustness of the pathway against thermal fluctuations and Rouse dynamics.

Conclusions:

• The designed pathway provides a method for the deterministic fabrication of complex metastable structures from block copolymers.
• This approach offers systematic exploration of accessible metastable structures based on molecular asymmetry and incompatibility.
• The findings are crucial for the controlled synthesis of advanced block copolymer materials.