Experimental and Molecular Simulation Studies of the Attachment Behavior of Photoinitiator XBPO Crystals in Different Solvents

The aggregation of crystals is a common phenomenon during the crystallization process. However, the formation mechanism of the aggregates remains elusive. In this work, we combine experiments with molecular simulations to investigate the attachment behavior of an organic compound photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (XBPO) in different solvents. The simulation results were highly in line with the experimental results. The results indicate that the aggregation behavior occurs on the high-energy surface (1 0 0) and the attachment angle is 0° during the solvothermal process. Meanwhile, solvents play the critical role in the formation of aggregated particles. It was found that the solvents with high Kamlet-Taft dipolarity/polarizability can promote the aggregation behavior of photoinitiator XBPO crystals. Furthermore, a solvent-mediated growth mechanism assisted by "oriented attachment"-like and Ostwald ripening mechanisms was proposed to elucidate the growth and aggregation of particles. We anticipate that this study will provide a comprehensive understanding of the attachment behavior and be helpful to control the aggregation of crystals.