Impact of Molecular Asymmetry of Block Copolymers on the Stability of Defects in Aligned Lamellae

Abstract

The stability of prototypical dislocation defects occurring in the ordered lamellar morphologies of block copolymers is of particular interest for both practical applications and fundamental research. Here, we study the impact of the segregation strength, compositional asymmetry, and architectural asymmetry on the evolution kinetics of single dislocation as well as the stability of its derivative disconnection defect occurring in the lamellar morphologies formed by AB diblock and AB 2 miktoarm star copolymers using self-consistent field theory coupled with the string method and single-chain-in-mean-field simulations. Our results indicate that the segregation strength generally increases the stability of the two defects, whereas the two other factors of asymmetry lower the stability of the single dislocation and significantly enhance the stability of the single disconnection due to the effect of spontaneous curvature. In particular, the single disconnection becomes metastable and can survive for a long period at intermediate segregation and thus may be promisingly applicable for the fabrication of regularly broken lines.

Solvent-assisted self-assembly of block copolymer thin films

“…288 This problem has been tackled theoretically, for various BCP chemistries and morphologies. [289][290][291][292][293] Self-consistent field theory (SCFT) is a major simulation method harnessed for SVA-assisted BCP ordering and has gained a separate review in the topic. 294 In a simulation work of lamellar BCP Peters et al calculated the defect annihilation rate for various segregation strength.…”

“…288 This problem has been tackled theoretically, for various BCP chemistries and morphologies. 289–293…”

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

“…We use the pseudospectral method of SCFT to calculate the free energy of these morphologies 53,54 and combined it with the string method to determine the possible free-energy paths connecting them. 33,35,45 In addition, we employ the single-chain-in-meanfield (SCMF) simulation to verify the predicted minimum freeenergy path (MFEP) of the defect evolution. 55−57 ■ THEORY AND METHOD Self-Consistent Field Theory (SCFT).…”

“…Though it is easy to experimentally characterize these static dislocations in the hexagonal pattern, it is challenging to monitor their evolution (e.g., occurring and annihilating), especially for those long-lived defects. The occurrence and annihilation of one defect depend on its thermodynamic and kinetic stabilities, respectively. ,,− In other words, the occurrence probability of one defect is determined by the excess free energy (Δ F d ) whose formation costs, and the annihilation kinetics is controlled by the free energy barrier (Δ F b ) that it needs to overcome when it evolves along the minimum free-energy path (MFEP). ,, Accordingly, theoretical methods have been developed for studying the thermodynamic and kinetic stabilities of the defects occurring in the ordered structures of block copolymers. Self-consistent field theory (SCFT) of Gaussian chain has become one of the most useful methods for the accurate calculation of the free energy of block copolymer structures.…”

Combining Particle-Based Simulations and Machine Learning to Understand Defect Kinetics in Thin Films of Symmetric Diblock Copolymers

“…This includes theoretical descriptions, all-atom and coarse-grained simulations, soft coarse-grained models, − continuum models, − and field-theoretic models. − Each of these methods serves an important role in understanding block polymers and their self-assembly. Recent publications summarize and address these efforts. − However, even with the use of modern supercomputers, they all struggle to predict the full kinetics of the self-assembly on laboratory time scales of hours or days. For diblock copolymers, the equilibrium phase diagram has been established with regular morphologies as a function of the block repulsion χ N and volume fraction f .…”