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

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journal contribution
posted on 05.11.2014, 00:00 by Lei Liu, Jun Jiang, Shu-Hong Yu
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.