Reversible Morphology Locking via Metal Infiltration in a Block Copolymer

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Block copolymers self-assemble into ordered nanostructures.
• Controlling these nanostructures is crucial for nanofabrication.
• Existing methods for morphology control can be limiting.

Purpose of the Study:

• To investigate a novel method for locking block copolymer morphologies.
• To explore the use of metal infiltration and exfiltration for morphology control.
• To demonstrate the reversibility of this locking mechanism.

Main Methods:

• Metal infiltration using a metal precursor (e.g., PtCl4^2-) in an acidic solution into poly(2-vinylpyridine) (P2VP) microdomains of a polystyrene-b-P2VP block copolymer.
• Solvent annealing to assess solvent vapor uptake and morphology locking.
• Metal exfiltration using a complexing solution (KOH + Na2EDTA).
• Multistage annealing processes to demonstrate reversibility with different metals (Pt, Fe).

Main Results:

• Metal infiltration significantly reduces solvent vapor uptake, effectively locking the block copolymer morphology.
• The extent of metal incorporation (e.g., Pt) is dependent on precursor and acid concentrations.
• Metal exfiltration restores solvent uptake and unlocks the morphology.
• The locking and unlocking process is reversible and demonstrated for both Pt and Fe.

Conclusions:

• Reversible metal infiltration provides a method to lock and unlock block copolymer microdomain morphologies.
• This technique enhances the utility of block copolymers in nanofabrication by allowing morphology stabilization during processing.
• The findings open new avenues for designing and controlling nanostructured materials.