Kinetic Monitoring of Block Copolymer Self-Assembly Using In Situ Spectroscopic Ellipsometry.

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Block copolymers (BCPs) self-assemble into ordered nanostructures.
• Understanding BCP self-assembly kinetics is vital but challenging due to limited in situ monitoring.
• Existing techniques struggle to differentiate assembly and disassembly during solvent annealing.

Purpose of the Study:

• To develop and validate a rapid in situ technique for monitoring BCP self-assembly kinetics.
• To investigate the influence of solvent-vapor annealing parameters on BCP domain formation and stability.
• To decouple the processes of BCP self-assembly and disordering during solvent-based processing.

Main Methods:

• Utilized spectroscopic ellipsometry (SE) to measure optical birefringence.
• Employed SE for rapid (1-second acquisition) in situ monitoring of BCP films during solvent-vapor annealing (SVA).
• Analyzed domain formation and disassembly kinetics as a function of solvent exposure time.

Main Results:

• SE successfully monitored domain formation and stability in cylinder- and lamellae-forming BCPs.
• Ordered BCP domains formed during SVA were stable in the swollen state but disordered upon rapid drying.
• Disordering kinetics during drying were found to be dependent on the duration of solvent exposure.

Conclusions:

• Spectroscopic ellipsometry provides a powerful tool for studying BCP self-assembly and disassembly kinetics.
• The duration of solvent exposure in SVA critically affects the final nanostructure order.
• SE enables the separation of self-assembly and disordering phenomena in BCPs during solvent annealing and evaporation.