Loose Bulk Density and Length-to-Diameter Ratio of Flexible Needle-like Crystals Crown via Antisolvent Crystallization

Low loose bulk density, a characteristic commonly observed in large accumulations of needle-like crystals, has caused numerous issues in both production processes and daily life. Antisolvent crystallization, known for its rapidity, localization, and minute crystals, presents particular challenges in enhancing the loose bulk density of needle-like crystals. In the study of β-nicotinamide mononucleotide, kinetic analyses reveal that the induction period varies significantly with antisolvent type, with the shortest induction period observed in methanol reaching as low as 0.0067 s. Thermodynamic studies indicate that its solubility in various antisolvent−water mixtures exhibits similar trends with changes in solvent composition, although the equivalent nucleation rates differ significantly. By simplifying the three-dimensional molecular exchange to one-dimensional and reducing the interfacial area between the solutions to slow the process, the resulting single crystals can attain a maximum size over 1000 times larger than the original microcrystals, making the flexible one-dimensional needle-like crystals prone to fracturing and reducing the length-to-diameter ratio. Similarly, when the actual three-dimensional molecular exchange within droplets is slowed, the crystal can grow significantly in size while being tightly assembled. Through crushing, the microscale flexible needle-like crystals can be completely broken down, reducing their length-to-diameter ratio, which in turn significantly increases the loose bulk density.