Synthesis and characterization of graft copolymers able to form polymersomes and worm-like aggregates

Abstract

Poly(glycerol adipate)-graft-(poly(ε-caprolactone)-block-poly(ethylene oxide)) (PGA-g-(PCL-b-PEO)) is synthesized by ring opening polymerization of ε-caprolactone initiated by the hydroxyl groups of PGA. This is followed by grafting of poly(ethylene oxide) monomethylether mPEO-N₃ onto the PCL blocks using copper-catalyzed azide–alkyne cycloaddition (CuAAC, “click” reaction). All polymers form micelles of radii in the range of 10 nm after dissolving in acetone and dialysis against water. Micelles formed by PGA-g-(PCL-b-PEO) show smaller critical micelle concentration (cmc) and higher stability against temperature increase compared to micelles formed by PCL-b-PEO with an identical chemical composition to the grafted segments. Additionally, PGA₁₇-g-(PCL₂₄-b-PEO₄₄) forms worm-like aggregates prepared by the cosolvent/evaporation method. The resulting worm-like aggregates are visualized by transmission electron and confocal laser scanning microscopy and show shape persistent behaviour over their entire contour length. It is suggested that these worm-like aggregates are formed by partially fused polymersomes under the influence of shear flow. They have the potential for simultaneous delivery of hydrophobic and hydrophilic drugs.