Mineralization of unique barium carbonate crystal superstructures controlled by a liquid crystalline phase polymer

Abstract

Barium carbonate (BaCO₃) crystals with unique hierarchical superstructures have been fabricated through a facile and controlled solution self-assembly mode in the presence of a tri-block copolymer PEO₇₀–PPO₂₀–PEO₇₀ (P₁₂₃). The powder X-ray diffraction (XRD) results revealed that the obtained BaCO₃ product was indexed to pure orthorhombic phase. Notably, BaCO₃ samples with well-defined hierarchical morphologies, including spherical, rod, hexangular prism, and porous spherical aggregates can be prepared by simply adjusting the polymer P₁₂₃ concentrations and the ratios of [Ba²⁺]/[P₁₂₃]. Specifically, layered screw cap, double-taper, and shuttle-shaped superstructures were formed through choosing N,N-bimethylformamide (DMF), tetrahydrofuran (THF), and/or toluene mixed with de-ionised water (DIW) as the reaction media in the current system, respectively. It is clearly demonstrated that varying liquid crystal-phase aggregating structures of the polymer P₁₂₃ and using different solvents can indeed exert a significant influence over the selective nucleation, crystal facets preferable adsorption, and consequent over-growth for the BaCO₃ primary particles. Moreover, a possible formation process for the hierarchical superstructures of BaCO₃ crystals is proposed.