Understanding Macroscopic Properties of Cucurbit[7]uril Solids in Anti‐Solvent Precipitation Based on Phase Diagram

ABSTRACT

This study investigated the relationship between operating conditions in anti‐solvent precipitation and the macroscopic properties of precipitated solids of cucurbit[7]uril (CB7), which has attracted considerable attention as a pharmaceutical and functional material, using a ternary phase diagram. The experimental results revealed that the external shape of the obtained particles varied with both the mixing ratio of the anti‐solvent and the mixing order of the solutions. In addition, it was demonstrated that the external shape is not determined solely by the concentration driving force. Based on these observations, we proposed that the properties of CB7 solids are influenced by the location of the operation point on the phase diagram and identified the region where CB7 solids with well‐defined facets preferentially precipitate. Characterization by x‐ray diffraction and dynamic light scattering indicated that CB7 solids with relatively high crystallinity were obtained only within the estimated region on the phase diagram. Overall, this study provides fundamental insights into controlling the macroscopic properties of CB7 solids by designing the operation point in anti‐solvent precipitation based on the phase diagram.