Capillary Force Lithography Pattern-Directed Self-Assembly (CFL-PDSA) of Phase-Separating Polymer Blend Thin Films

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Patterning immiscible polymer blend films is crucial for advanced material applications.
• Achieving highly ordered, phase-separated morphologies in polymer blends remains a challenge.

Purpose of the Study:

• To introduce a facile technique, capillary force lithography pattern-directed self-assembly (CFL-PDSA), for creating ordered phase-separated morphologies in polymer blend films.
• To investigate the influence of blend composition and annealing time on the self-assembly process.

Main Methods:

• Utilized capillary force lithography (CFL) with a patterned poly(dimethyl siloxane) (PDMS) stamp to confine polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend films.
• Annealed the confined films above the glass transition temperature of both polymers to induce phase separation guided by preferential wetting and stamp topography.
• Analyzed the resulting phase-separated morphology under pattern confinement.

Main Results:

• Achieved a perfect negative replica of the stamp pattern in all tested conditions.
• Demonstrated well-controlled, vertically patterned phase separation driven by the preferential wetting of PS to PDMS and PMMA to the silicon substrate.
• Observed that phase-separated domain morphology is influenced by blend composition and annealing time, with domain coarsening occurring over time.
• Determined that optimal morphology control is achieved when the blend ratio matches the volume ratio of the elevated and base regions of the patterned film.

Conclusions:

• CFL-PDSA is an effective and facile method for producing highly ordered phase-separated morphologies in immiscible polymer blends.
• The technique offers precise control over vertical phase separation through preferential wetting and stamp-guided self-assembly.
• The process is adaptable for roll-to-roll compatibility, suggesting potential for industrial adoption in advanced material fabrication.