A mesoscale self-assembly into bulk bassanite via delicate control of water activity to mimic biomineralization

Metastable bassanite cannot usually be precipitated from aqueous solutions, yet easily taking up water to yield the gypsum. Although biological systems can mineralize this phase to micron sized crystals, a facile fabrication of bulk bassanite in vitro under ambient conditions remains a major challenge. Here, we unprecedentedly fabricated the bulk phase of bassanite by precisely controlling the water limited in the solution with polymer (polyvinyl pyrrolidone), suppressing the transformation into thermodynamically favourable gypsum. A new thermodynamic model of the non-classical crystallization process is described in terms of water-driven colloidal assembly, and molecular dynamics simulation demonstrates the role of water molecules to interact with the polymer ligands to initiate the assembly and growth of bassanite. These findings contribute to a deeper understanding of how the bassanite precipitates in vivo and may save us the procedure of thermally transforming about hundreds of millions of tons of dihydrate per year into hemihydrate