Morphology control in block copolymer films using mixed solvent vapors.

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Block copolymer thin films exhibit morphologies influenced by processing conditions.
• Solvent vapor annealing (SVA) offers a route to control nanostructure formation.
• Equilibrium bulk morphology may not be achievable or desirable in thin films.

Purpose of the Study:

• To investigate the effect of solvent vapor annealing conditions on block copolymer thin film morphologies.
• To establish phase maps correlating morphology with solvent vapor pressure and annealing parameters.
• To understand the role of solvent-induced swelling in morphology development.

Main Methods:

• Systematic variation of solvent vapor (toluene, n-heptane) flow rates and inert gas flow.
• Construction of morphology phase maps for polystyrene-block-polydimethylsiloxane diblock copolymers.
• Correlation of final morphology with film swelling and annealing conditions.
• Modeling of solvent swelling effects using self-consistent field theory.

Main Results:

• Phase maps reveal distinct morphology regions based on solvent vapor pressure and annealing parameters.
• Film swelling is directly correlated with solvent vapor annealing conditions and influences final morphology.
• A range of non-equilibrium morphologies can be accessed through controlled SVA.
• Self-consistent field theory successfully models the impact of solvent swelling.

Conclusions:

• Solvent vapor annealing provides a versatile method for controlling block copolymer thin film morphologies.
• The established phase maps offer a predictive framework for achieving desired nanostructures.
• Understanding swelling is crucial for tailoring morphologies for applications like nanolithography.