Preparation and characterization of cross-linked hollow poly(lactic acid) microspheres

Poly (lactic acid) macromonomer with a double bond at its end was synthesized by ring open polymerization of lactide catalyzed by stannous chloride in the presence of allyloxylethanol(AOE) as a coinitiator. Its molecular weight was decreased along with the adding amount of AOE. Initiated by an oxidation-reduction system, e. g. K2S2O8 and Na2SO3, the poly (latic acid) macromonomers were copolymerized with divinylbenzene and methacrylic acid in a water-in-oil-in-water emulsion manner to produce hollow microspheres with a size of hundreds nanometers. Their hollow structure was confirmed by transmission electron microscopy. Infrared spectroscopy measurement shows that the remainings of the microspheres after tetrahydrofuran extraction, constituting roughly 20% of the sphere's mass, contained all the initial monomer components. This provides a new pathway for fabricating biodegradable hollow microspheres with rather smaller size, which may find diverse applications in the fields of drug delivery, tissue engineering and nanotechnology.