Morphology control of trimer particles via one-step co-precipitation and controlled phase separation

Nanoprecipitation is a flexible method to prepare biocompatible nanoparticles (NPs) for drug delivery and so on. However, it is generally hard to co-precipitate multiple polymers due to their different solvent solubility. Here, shellac/PLA/PS trimer NPs are prepared for the first time via one-step co-precipitation upon rapid solvent exchange and controlled phase separation. The morphology of shellac/PLA/PS NPs strongly depends on the interfacial tensions between different phases and could be tuned by the molecular surfactant added in the continuous aqueous phase. Since co-precipitation is a fast process, a high temperature is preferred for the system to reach the thermal equilibrium state; otherwise, the system may kinetically be locked in an intermediate state. The influences of polymer molecular weight and interfacial tension are also investigated in detail to reveal the underlying mechanisms of preparing shellac/PLA/PS trimer NPs with linear or triangular structures. This study will shield new light on the design and preparation of NPs with more diverse compositions and more complex structures via one-step co-precipitation and controlled phase separation and further expand the potential applications of NPs.