Polymorph Selection and Structure Evolution of CaCO₃ Mesocrystals under Control of Poly(sodium 4‑styrenesulfonate): Synergetic Effect of Temperature and Mixed Solvent

The synergetic effects of water/ethanol mixed solvent and crystallization temperature upon CaCO₃ polymorph discrimination and structural assembly under control of poly­(sodium 4-styrene­sulfonate) (PSS) were examined. CaCO₃ mesocrystals of all three anhydrous polymorphs (calcite, aragonite, and vaterite) with progressively developed morphologies can be selectively realized in one system by consecutively decreasing the water/ethanol volume ratio (R) at the proper temperature. At a lower crystallization temperature (10 °C), decreasing the R value resulted in a polymorph transition of CaCO₃ from pure calcite to pure vaterite, which was mainly attributed to the increased ethanol content and the resulting conformation change of PSS molecules. In contrast, CaCO₃ polymorphs changed from pure calcite to almost pure aragonite at higher crystallization temperature (40 °C), where the temperature effect was more obvious and became the dominant parameter for CaCO₃ polymorph selection. In addition, a dipole effect was employed to explain the formation of calcite and vaterite mesocrystals with continuously and increasingly developed superstructures. This study could have important implications in the design and preparation of a great deal of inorganic materials with well-defined morphologies, polymorphs, and ordered arrangement that can be controlled by simply adjusting the reaction media and temperature.