Controlled crystallization of vaterite from viscous solutions of organic colloids

Precipitation of calcium carbonate from hydroxyethyl cellulose (HEC) containing aqueous solutions of CaCl₂ and Na₂Co₃ resulted in an uncommon polymorph, vaterite. In contrast to precipitations without HEC, crystallization in the presence of HEC led to a shell-shaped body consisting of organized vaterite platelets. The artificial shell is a composite of stacks of vaterite and about 2% HEC. In the experimental arrangement used, HEC controlled both nucleation and crystal growth of vaterite. Concentration of HEC also affected the platelet's thickness which in turn influenced the shell's morphology as well. These results demonstrate the importance of organic-inorganic interface in controlling crystallization.