Crystallization of CaCO₃ Mesocrystals and Complex Aggregates in a Mixed Solvent Media Using Polystyrene Sulfonate as a Crystal Growth Modifier

Crystallization behavior of calcium carbonate (CaCO 3 ) in water/ethanol mixed solutions under ambient conditions using polystyrene sulfonate (PSS) as a crystal growth modifier has been systematically investigated. The results have demonstrated that a switch from thermodynamic control to kinetic control in the crystallization process of CaCO 3 can be easily realized by adding ethanol, which can have a significant influence on the polymorphs and morphologies of CaCO 3 crystals. Calcite mesocrystals and vaterite complex aggregates with increasingly developed shapes can be obtained with an increase of the ethanol content in the solution. The polymorph change of CaCO 3 crystals from pure calcite to a calcite dominated mixture and finally to a vaterite dominated mixture has also been nicely captured. Both CaCO 3 crystals with different evolving phases and the polymorph change of CaCO 3 from calcite to vaterite can be attributed to the balance between thermodynamic control and kinetic control in this special crystallization media. This work sheds light on the possibility of adding ethanol to control the kinetic/thermodynamic balance and thus to possibly control the morphologies and polymorphs of a wide range of inorganic materials.