Elucidating Reaction Pathways in the Synthesis of Block Copolymer-Derived Crystalline Inorganic Materials via In Situ SAXS/WAXS and XAS

Block copolymer-inorganic hybrid co-assembly is a tunable, versatile basis for synthesis of ordered mesoporous transition metal oxides and nitrides used in electrochemical energy conversion and storage, catalysis, and discovery of novel electronic properties. Despite decades of experimental work in the synthesis such materials, the interplay of crystallinity and mesostructure retention during high temperature treatments remains a significant challenge for further fundamental and applied studies on such materials. For example, the only route to superconducting block copolymer-derived mesoporous niobium nitride involves a poorly-understood two step heat treatment in flowing ammonia gas at temperatures above 850 C to produce materials with a significantly depressed superconducting transition. We have employed in situ small- and wide- angle X-ray scattering and XANES during such anneals to elucidate reaction pathways and synthesize materials with improved transition temperature and mesostructure retention. These studies have also allowed the expansion of this process from custom-synthesised ABC triblock terpolymers to commercially available Pluronic ABA triblock copolymers, enabling the broader application of block copolymer-derived mesoporous nitrides.