Crystallization and stereocomplexation governed self-assembling of poly(lactide)-b-poly(ethylene glycol) to mesoscale structures

The stereocomplex formation between enantioselective poly(lactide) (PLA) homopolymers is well understood. In this report an attempt is made to analyze the influence on the self-assembling of the stereocomplex of enantiomorphic PLA-PEG di- and tri-blocks in different solvents. Powder diffraction studies showed the poly(ethylene glycol) (PEG) and the PLA blocks crystallize separately forming unique supra structures like rods, discs and coiled coils with dimensions in the micrometer scale in length and sub-micrometer scale in diameter. The influence of the solvents on the crystal formation was shown in the formation of uniform structures. Discs emerged from equimolar mixtures of the D- and L-configured di- and tri-block copolymers, in dioxan and acetonitrile and in water the stereocomplexes crystallized mainly as rods. In some cases the rods were observed as coiled coils. The shape, the hydrophobic/hydrophilic content and the PEG coated surface of the discs give them a future potential as matrix for the controlled and targeted delivery of bioactive agents.