Self-assembly of AB diblock copolymers under confinement into topographically patterned surfaces

Area of Science:

• Polymer Science
• Materials Science
• Computational Physics

Background:

• Block copolymers exhibit microphase separation and form ordered structures.
• Nanoimprinting experiments have shown potential for creating patterned copolymer films.
• Understanding confined copolymer behavior is crucial for advanced material design.

Purpose of the Study:

• Investigate microphase separation and morphology of symmetric AB diblock copolymers under confinement.
• Explore the influence of a square-wave patterned top surface on copolymer structures.
• Identify new microstructures formed by confinement and surface fields.

Main Methods:

• Employed self-consistent field theory (SCFT) to model copolymer behavior.
• Utilized an efficient pseudospectral method for solving SCFT equations in complex geometries.
• Implemented a "masking" technique to handle irregularly shaped confined domains.

Main Results:

• Observed inverted T-style and trapezoid structures dependent on surface field strength.
• Identified parallel lamellae formation under specific confinement conditions (neutral walls).
• Discovered novel structures like square, partial square, and reversed-T patterns under confinement.

Conclusions:

• Topographically patterned surfaces and surface fields can guide the formation of desired block copolymer microstructures.
• Confinement width and block-substrate interactions are critical parameters for controlling morphology.
• Findings provide a roadmap for designing block copolymer materials using nanoimprinting.