Micellar Formation in Aqueous Milieu from Biodegradable Triblock Copolymer Polylactide/Poly(ethylene glycol)/Polylactide

The formation of polylactide/poly(ethylene glycol)/polylactide (PLA/PEG/PLA) triblock copolymer micelles in aqueous milieu was studied by a combination of fluorescent probe, dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. The fluorescence spectroscopy measurements showed that the PLA/PEG/PLA triblock copolymers were associated to form core-shell type polymeric micelles in water and the critical micelle concentration (CMC) values changed relatively little with increasing PEG chain length in the block copolymers. From dynamic light scattering investigations, the size of polymeric micelles was influenced by the molecular weights and the composition of two components of the triblock copolymers. The size of micelles increased with increasing PLA chain length in the block copolymer. Transmission electron microscopy observations revealed the formation of spherical micelles. The triblock copolymer underwent degradation after 13 days of hydrolysis in phosphate buffer solution (PBS). The degradation influenced the size distribution and the morphology of the micelles.