Synthesis and characterization of linear and branched copolymers of poly(ethylene glycol) and poly(ε-caprolactone)

Linear and branched copolymers consisting of poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) were prepared to compare the characterization of star-shaped copolymers with various molecular architecture. Linear and branched PEG-PCL (1-arm, 2-arm, 4-arm, and 8-arm) copolymers were synthesized by the ring-opening polymerization of ε-caprolactone in the presence of HCl · Et₂O as a monomer activator at room temperature. The synthesized copolymers were characterized with ¹H-NMR, GPC, DSC, and XRD. As a result of the DSC and XRD, each copolymers showed different thermal properties and crystallinity according to the number of arms. The micellar characterization of linear and branched copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering, AFM, and fluorescence techniques. The critical micelle concentration (CMC) and diameters of micelles depended on the number of arms. Most micelles exhibited a spherical shape in AFM. In this study, we characterized star-shaped PEG-PCL copolymers and investigated their molecular architecture effect on the various properties. Furthermore, we confirmed that the micelles formed with linear and branched PEG-PCL copolymers have possibility as a potential hydrophobic drug delivery vehicle.