Melt brushes of diblock copolymer

Area of Science:

• Polymer Physics
• Materials Science
• Surface Science

Background:

• Block copolymers form complex morphologies due to phase separation.
• Grafting copolymers to surfaces introduces confinement effects, altering morphology.
• Understanding these surface-confined structures is crucial for advanced materials design.

Purpose of the Study:

• To investigate the surface morphologies of AB diblock copolymer brushes grafted to a flat substrate.
• To explore the influence of system parameters like incompatibility and grafting density on morphology.
• To compare the phase behavior of tethered films with bulk diblock copolymer systems.

Main Methods:

• Utilized self-consistent field theory (SCFT), a powerful computational tool for polymer systems.
• Simulated a melt brush of AB diblock copolymers tethered to a flat substrate via their B blocks.
• Analyzed the phase diagram as a function of A/B incompatibility (chiN) and diblock composition (f).

Main Results:

• Identified a laterally uniform morphology alongside three ordered morphologies: hexagonal A-rich dots, alternating A/B stripes, and hexagonal B-rich dots.
• The phase diagram of the tethered film mirrors the bulk phase diagram, with periodic phases converging at weak segregation.
• Periodic phase regions shrink with increased grafting density and expand with enhanced surface affinity for B blocks.

Conclusions:

• SCFT successfully predicts diverse ordered surface morphologies in grafted diblock copolymer brushes.
• The system exhibits phase behavior analogous to bulk diblock copolymers, but with distinct surface-driven ordering.
• Grafting density and surface interactions are key parameters controlling the formation and stability of these ordered structures.