Hollow Polylactide Microcapsules with Controlled Morphology and Thermal and Mechanical Properties

Hollow polylactide microcapsules were prepared by multistage premix membrane emulsification of polylactide/dichloromethane/oil solutions in water (nonsolvent). The effects of the different oils on the morphology, thermal, and mechanical properties of the hollow microcapsules were investigated. All oils resulted in hollow microcapsules with controlled shell thickness of 60 nm except for eugenol, in which irregular, massive capsules were obtained. The properties of the microcapsules were strongly dependent on the oil used, for example the thermal transition temperatures found for hollow capsules were lower than for solid particles prepared without any oil. The crystallinity and transition temperatures of the capsules prepared with linear alkanes were higher than for cyclic alkanes; terpenes gave the lowest transition temperatures. The shell stiffness, measured with atomic force microscopy, was highly dependent on the oil used. Capsules prepared with dodecane showed higher stiffness (3.3 N m-1) than with limonene (2 N m-1) or cyclohexane (1.4 N m-1)