Crystallization-Driven Formation of Diversified Assemblies for Supramolecular Poly(lactic acid)s in Solution

Precipitation (or solvent displacement) method has been a simple yet efficient way to prepare the micro- and nanoparticles of polymers. However, control over the particle morphology of semicrystalline polymer is extremely challenging in the precipitation method, due to the interplay of polymer crystallization with liquid–liquid phase separation in solution. This limits the preparation of polymer particles with well-controlled morphology. Herein we report on the preparation of flower-shaped and spherical biodegradable polymer particles by precipitating the ureido-4­[1H]-pyrimidione-functionalized supramolecular poly­(lactic acid) (PLA) from a good solvent to an antisolvent. Morphology of PLA particles was successfully manipulated by the solution crystallization, molecular weight, and intermolecular interactions of polymer precursors. Homocrystallization of supramolecular poly­(l-lactic acid) yielded the flower-shaped particles in precipitation; yet stereocomplex crystallization of PLA supramolecular copolymers led to the formation of sphere particles. The underlying mechanism for crystallization-driven formation of various particles was proposed. The prepared sphere particles can be used as the carriers of hydrophobic drug. Degradation and drug release rates of the prepared PLA particles decreased with increasing the content of stereocomplexes. Our study paves a way to the biodegradable PLA particles with controllable morphologies that may find potential applications in biomedical field.