Annihilation Kinetics of an Interacting 5/7-Dislocation Pair in the Hexagonal Cylinders of AB Diblock Copolymer

Abstract

The annihilation kinetics of an interacting 5/7-dislocation pair with oppositely apposing Burgers vectors in a well-aligned hexagonal lattice of cylinders formed by asymmetric AB diblock copolymers is investigated by theory and simulation. The defect morphology evolves into the defect-free pattern through a fission or nucleation mechanism to add those missing domains. The results of the minimum free energy path (MFEP) reveal that the evolution of the defect is more likely to follow the M-type path along which the two dislocations approach each other during the evolution, rather than the N-type along which they evolve separately. Moreover, the free energy barrier for creating one new domain via fission is more sensitive to the separation (i.e., interaction) between the two dislocations than that via nucleation. When increasing the volume fraction of cylinders, we find that the defect evolution exclusively chooses the M-type MFEP via the fission mechanism. The MFEP results are confirmed by dynamic simulations based on the single-chain-in-mean-field method. Our work gives insight into the understanding on the annihilation mechanism of the interacting defects in the hexagonal cylinder morphologies.

Transition Paths of Ordered Phases in a Diblock Copolymer under Cylindrical Confinement

“…In the past decades, the thermodynamics and kinetics of defect motion and annihilation in the directed self-assembly (DSA) of block copolymer systems have been intensively studied, using the combination of SCFT and the string method. − Besides these block copolymer thin film systems, Cheng et al explored the kinetic evolution of various ordered phases in block copolymers, e.g., cylinders ↔ gyroids, lamellae → cylinders, lamellae → gyroids . Yao et al studied the transition paths in the cylinder–gyroid interface .…”