Morphology manipulation in block copolymer films by reversible metal infiltration

Block copolymers (BCPs) are enablers of nanofabrication and pattern transfer processes owing to the ordered nanoscale structures that they form by self-assembly. We show that the self-assembled structures of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) BCPs can be locked by infiltrating [PtCl₄]²⁻ from a HCl solution. Pt infiltrates the P2VP block, limiting chain mobility and therefore locking the microdomain structure against reorganization during a successive annealing process. The amount of Pt introduced into the P2VP increases with both metal precursor concentration and acid concentration, reaching 0.83 Pt atom per pyridine group. A reverse exfiltration process using a KOH + ethylenediaminetetraacetic acid disodium salt dihydrate (Na₂EDTA) complexing solution unlocks the structure and allows the microdomains to reorganize in a subsequent annealing step, for example, annealing in a different solvent vapor to change the morphology. The reversibility of metal infiltration and the corresponding morphology locking and unlocking effect is validated by characterizing the morphological evolution during multi-step annealing, infiltration and exfiltration steps, and in a 3D structural design process in which multiple layers of PS-b-P2VP are assembled with different morphologies. Structural locking and unlocking via infiltrated metal diversifies the toolkit for BCP-enabled nanofabrication.