Hole nucleation in thin diblock copolymer films.

Area of Science:

• Materials Science
• Polymer Science
• Physical Chemistry

Background:

• Homogeneous nucleation is a fundamental process in materials formation.
• Understanding nucleation mechanisms in thin films is crucial for advanced material design.
• Diblock copolymers offer a versatile platform for studying phase transitions and self-assembly.

Purpose of the Study:

• To experimentally investigate the molecular-level mechanisms of homogeneous nucleation in diblock copolymer thin films.
• To characterize the evolution of nucleated patterns, specifically holes, and their associated surface topography.
• To elucidate the distinct growth regimes following hole nucleation.

Main Methods:

• Utilized atomic-force microscopy (AFM) for direct-space observation of nucleation and hole evolution.
• Employed Neutron Reflectivity experiments to confirm the presence of compressed internal layers.
• Analyzed nucleus surface topography at various developmental stages.

Main Results:

• Observed hole formation in thin diblock copolymer films, preceded by surface bumps.
• Identified ordered metastable states involving compressed internal layers and central pores with interfacial flows.
• Characterized two distinct post-nucleation hole growth regimes: individual and interactive.

Conclusions:

• Proposed a detailed molecular-level nucleation mechanism for diblock copolymer films.
• Confirmed the role of compressed internal layers and pore formation in the nucleation process.
• Established the existence of two distinct hole growth dynamics, providing insights into film morphology development.