Structure and mechanical properties of polylactide copolymer microspheres and capsules

Polylactide homopolymers, polylactide and poly(ethylene oxide) diblock and triblock copolymers are used to prepare spherical microparticles by using the single oil-in-water emulsion and solvent evaporation technique. We are able to create both bulk and hollow microspheres by altering the conditions of preparation. The experiments are carried out at two fixed temperatures of 15 and 22 °C. We show, from scanning electron microscopy data, that the microspheres produced from the homopolymers are bulk and homogeneous at both temperatures whereas they are hollow when the triblock copolymers are used. The diblock copolymers yield bulk microspheres at 15 °C and microcapsules at 22 °C. Compression experiments emphasize once more the inner morphology of the spheres. As it is expected, bulk microspheres have higher Young’s modulus than the microcapsules. Nevertheless, comparative compression analysis of both morphologies shows that the microcapsules retain relatively high compressive moduli. These results have implications for the design of rigid and biodegradable microcapsules.