Synthesis and Characterization of Linear-Dendron-like Poly(ε-caprolactone)-b-poly(ethylene oxide) Copolymers via the Combination of Ring-Opening Polymerization and Click Chemistry

A new class of linear-dendron-like poly(ε-caprolactone)- b -poly(ethylene oxide) (PCL- b -PEO) copolymers with unsymmetrical topology was synthesized via controlled ring-opening polymerization (ROP) of ε-caprolactone (CL) followed by a click conjugation with azide-terminated PEO (PEO-N 3 ). The dendron-like PCL terminated with a clickable alkyne group (D m -PCL, m = 0, 1, 2, and 3) was for the first time synthesized from the ROP of CL monomer using a propargyl focal point dendrons D m with primary amine groups as the initiators and stannous octoate as catalyst in bulk at 130 °C. Then, the linear-dendron-like D m -PCL- b -PEO copolymers were obtained by the click conjugation of D m -PCL with PEO-N 3 using PMDETA/CuBr as catalyst in DMF solution at 35 °C. Their molecular structures and physical properties were in detail characterized by FT-IR, NMR, MALLS-GPC, DSC, and WAXD. Both DLS and TEM analyses demonstrated that the biodegradable micelles and vesicles with different sizes (less than 100 nm) self-assembled from these D m -PCL- b -PEO copolymers in aqueous solution, and both the PEO composition and the linear-dendron-like architecture of copolymers controlled the morphology and the average size of nanoparticles. To the best of our knowledge, this is the first report that describes the synthesis of linear-dendron-like PCL- b -PEO block copolymers via the combination of ROP and click chemistry. Consequently, this provides a versatile strategy not only for the synthesis of biodegradable and amphiphilic block copolymers with linear-dendron-like architecture but also for fabricating biocompatible nanoparticles with suitable size for controlled drug release.