Crosslinking ionic oligomers as conformable precursors to calcium carbonate

Inorganic materials have essential roles in society, including in building construction, optical devices, mechanical engineering and as biomaterials1–4. However, the manufacture of inorganic materials is limited by classical crystallization5, which often produces powders rather than monoliths with continuous structures. Several precursors that enable non-classical crystallization—such as pre-nucleation clusters6–8, dense liquid droplets9,10, polymer-induced liquid precursor phases11–13 and nanoparticles14—have been proposed to improve the construction of inorganic materials, but the large-scale application of these precursors in monolith preparations is limited by availability and by practical considerations. Inspired by the processability of polymeric materials that can be manufactured by crosslinking monomers or oligomers15, here we demonstrate the construction of continuously structured inorganic materials by crosslinking ionic oligomers. Using calcium carbonate as a model, we obtain a large quantity of its oligomers (CaCO3)n with controllable molecular weights, in which triethylamine acts as a capping agent to stabilize the oligomers. The removal of triethylamine initiates crosslinking of the (CaCO3)n oligomers, and thus the rapid construction of pure monolithic calcium carbonate and even single crystals with a continuous internal structure. The fluid-like behaviour of the oligomer precursor enables it to be readily processed or moulded into shapes, even for materials with structural complexity and variable morphologies. The material construction strategy that we introduce here arises from a fusion of classic inorganic and polymer chemistry, and uses the same cross-linking process for the manufacture the materials. The crosslinking of oligomeric precursors, controlled by a capping agent, enables the production of moulded crystalline calcium carbonate with continuous structures.