Engineering Three-Dimensional Morphologies in a Block Copolymer by Reversible Metal Infiltration

A range of three-dimensional (3D) morphologies is established in layered thin films of a block copolymer, polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) (115 kg/mol, P2VP volume fraction 31.6%), by combinations of spin coating, solvent annealing, reversible metal infiltration, and surface modification by oxygen etching. Pt infiltrated into the cylindrical-morphology P2VP blocks from an acid solution containing [PtCl4]2– locks the morphology of the bottom layer during the coating and annealing of a second layer, leading to a range of bilayered and trilayered 3D structures, including in-plane orthogonal meshes and layered I-shape and inverted T-shape P2VP microdomains. In contrast, unloading the metal by a KOH plus ethylenediaminetetraacetic acid disodium salt dihydrate (Na2EDTA) solution allows chain reorganization during subsequent layer coating and annealing, producing morphologies characteristic of a single layer of the PS-b-P2VP. However, a short oxygen etch modifies the surface, impedes chain reorganization, and yields multilayer structures even when the metal unloading process is performed. Metal infiltration and exfiltration combined with layering, annealing, and oxygen etching diversify the morphologies available from the block copolymer and provide a path to localized morphology control, expanding the toolkit for 3D nanofabrication.