AbstractA Polymer-Induced Liquid-Precursor (PILP) process for mineralization of calcium carbonate has been studied in-situ by laser light scattering. Static and dynamic light scattering data were obtained from CaCl2 solutions containing poly(aspartic acid). Under these conditions calcium carbonate mineralizes through a liquid droplet precursor phase when the solution is exposed to the decomposition products of ammonium carbonate. Our measurements probe the integrated scatterer mass and the apparent hydrodynamic radius Rh,app of the droplets as they nucleate and coalesce. The data reveal three stages in the formation of the PILP phase: an early stage of droplet growth to Rh,app ≈ 250 nm; a mid-time stage of fluctuations and polydispersity in particle size; and a final growth period where Rh,app increases from 350 nm to the micron scale. Aggregation of precursor droplets, rather than atom-by-atom growth, is the dominant mechanism of mineral formation under these conditions. With respect to biomineralization, this first observation of 100-nm-scale droplets is significant, implying a possibility to mineralize from the liquid phase within the nanoscale compartments in which many biominerals form.
