Publication Details

Abstract: Liquid-liquid phase separation (LLPS) is an intermediate step during the precipitation ofcalcium carbonate, and is assumed to play a key role in biomineralization processes. Here, we developed a model where homogeneous phase ion association thermodynamics determines the liquid-liquid miscibility gap of the aqueous calcium carbonate system, verified experimentally using potentiometric titrations,and kinetic studies based on stopped-flow ATR-FTIR spectroscopy. The proposed mechanism explains varying solubilities of solid amorphous calcium carbonates,reconciling previously inconsistent literature values. Accounting for liquid-liquid amorphous polymorphism, the model also provides clues to the mechanism of polymorph selection. Itis general and should be tested for other systems than calcium carbonate,providing a new perspective on the physical chemistry of LLPS mechanisms—based on stable pre-nucleation clusters rather than un-/metastable fluctuations—in biomineralization,and beyond.