Ordering Dynamics of Directed Self-Assembly of Block Copolymers in Periodic Two-Dimensional Fields

Abstract

The ordering dynamics of directed self-assembly of cylinder-forming diblock copolymers is studied by cell dynamics simulations. The directing field, mimicking chemically or topologically patterned substrates, is in the form of hexagonally arranged potential wells attractive to minority blocks. Time evolution of the defect concentration is used to characterize the ordering dynamics of the self-assembled cylindrical structures of the block copolymers. When the period of the external potential, Ls, is a small integer multiple of the cylinder-to-cylinder distance, L0, of the block copolymer microphase, the defect concentration decays exponentially. The defect annihilation becomes slower as Ls is increased, and eventually, the exponential decay law is broken. When the ratio Ls/L0 is a square root of an integer, large polycrystalline grains with different orientations are observed. The results are consistent with available experimental and theoretical results.