Fabrication of composite particles by liquid–liquid interfacial crystallization using an ultrasonic spray nozzle

• Ultrasonic crystallization improved the coating efficiency on composite particles.
• The size of composite particles was independent of contact time.
• Larger particles were produced by increasing the concentration of glycine.
• Glycine polymorphism could be controlled by the organic solvent temperature.
• Interaction between the core particles and guest particles was a key factor.

The purpose of this study was to produce composite particles, consisting of core starch particles coated with glycine, by liquid–liquid interfacial crystallization with an ultrasonic spray nozzle and to investigate the effect of operating conditions on glycine particle morphology. We confirmed that ultrasonic irradiation could improve the coating efficiency of the core starch particles during the crystallization process. We also investigated the transformation between different polymorphs of glycine crystals that covered the starch surface. The coating efficiency of the fine glycine crystals on the starch particles was improved by using an ultrasonic spray nozzle rather than anti-solvent crystallization without an ultrasonic spray nozzle. The glycine crystals on the surface of starch particles transformed from unstable to stable forms according to the solution-mediated mechanism and Ostwald rule of stages. The interaction between the core particles and guest particles was found to be a key factor in producing the composite particles. The results indicate that this crystallization process using the ultrasonic spray nozzle is promising for efficiently producing composite particles.

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