Versatile Strategy for the Synthesis of Dendronlike Polypeptide/Linear Poly(ε-caprolactone) Block Copolymers via Click Chemistry

A new class of dendron-like polypeptide/linear poly(epsilon-caprolactone) block copolymers with asymmetrical topology (i.e., dendron-like poly(gamma-benzyl-L-glutamate)/linear PCL copolymers having 2(m) PBLG branches, m = 0, 1, 2, and 3; denoted as PCL-Dm-PBLG) was for the first time synthesized via the combination of controlled ring-opening polymerization (ROP) of epsilon-caprolactone, click chemistry, and the ROP of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA). The linear hydroxyl-terminated PCL (PCL-OH) was synthesized by controlled ROP of epsilon-caprolactone and then transformed into clickable azide-terminated PCL (PCL-N-3). The PCL-N-3 precursor was further click conjugated with propargyl focal point PAMAM-typed dendrons (i.e., Dm having 2(m) primary amine groups) to generate PCL-dendrons (PCL-Dm) using CuBr/PMDETA as catalyst in dimethylformamide solution at 35 degrees C. Finally, PCL-Dm was used as macroinitiator for the ROP of BLG-NCA monomer to produce the targeted PCL-Dm-PBLG block copolymers. Their molecular structures and physical properties were characterized in detail by FT-IR, NMR, matrix assisted laser desorption ionization time-of-flight mass spectrometry, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. To the best of our knowledge, this is the first report that describes the synthesis of dendron-like polypeptide/linear PCL block copolymers with asymmetrical topology via the combination of ROP and click chemistry. Consequently, this provides a versatile strategy for the synthesis of biodegradable and biomimetic dendron-like polypeptide-based biohybrids.