A surface interaction model for self-assembly of block copolymers under soft confinement.

Area of Science:

• Polymer Science
• Materials Science
• Surface Science

Background:

• Surface interactions critically influence block copolymer self-assembly and domain alignment in thin films.
• Previous models simplified grafted polymer surfaces as hard walls, limiting understanding of their role.
• Grafted polymers on substrates significantly impact the behavior of self-assembling block copolymers.

Purpose of the Study:

• To develop a general model for surface interactions in block copolymer systems.
• To investigate the distinct contributions of surface preference and surface softness.
• To analyze the alignment of lamellar domains in symmetric diblock copolymers on modified substrates.

Main Methods:

• Utilized self-consistent field theory (SCFT) for numerical analysis.
• Modeled substrates modified by homopolymers.
• Investigated the stability competition between perpendicular and parallel lamellar orientations.

Main Results:

• A novel model decomposes surface interactions into surface preference and surface softness.
• Phase diagrams reveal the impact of these parameters on lamellar domain alignment.
• Identified a significant parameter window for achieving stable perpendicular lamellae, even on preferential substrates.

Conclusions:

• The proposed model provides a more complete understanding of surface effects on block copolymer alignment.
• Surface preference and softness are key independent factors controlling domain orientation.
• This work offers pathways to precisely engineer substrate properties for desired self-assembly outcomes.