Infiltration Synthesis of Diverse Metal Oxide Nanostructures from Epoxidized Diene-Styrene Block Copolymer Templates

Infiltration synthesis is a class of block copolymer lithography in which block copolymer templates are selectively infiltrated with metal or metal oxide precursors, which has been proposed as a method for the production of nanometer-scale patterns of metal oxides with higher throughput and lower cost than existing lithographic methods. Infiltration synthesis has almost exclusively been studied with polystyrene-block-poly(methyl methacrylate) block copolymer templates, which have limitations in the metal oxides that can effectively be templated. We have found that polystyrene-block-poly(epoxyisoprene) (PS-b-PIO) copolymers prepared by epoxidation of polystyrene-block-poly(1,4-isoprene) (PS-b-PI) copolymers are readily accessible block copolymer templates for the direct infiltration synthesis of not only aluminum oxide from trimethylaluminum but also zinc oxide from diethylzinc, titanium oxide from titanium tetraisopropoxide, and vanadium oxide from vanadium oxytriisopropoxide. PS-b-PI copolymers were also found to effect patterning with trimethylaluminum and diethylzinc, which we attribute to selective miscibility of the nonpolar metal alkyls in the polydiene domains. From these results, we infer that general miscibility of the metal oxide precursor with the copolymer as well as specific acid-base interactions between the metal oxide precursor and the copolymer contribute to the higher efficacy of infiltration synthesis using PS-b-PIO.