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

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journal contribution
posted on 11.05.2009 by Chong Hua, Chang-Ming Dong, Yen Wei
A new class of dendron-like polypeptide/linear poly(ε-caprolactone) block copolymers with asymmetrical topology (i.e., dendron-like poly(γ-benzyl-l-glutamate)/linear PCL copolymers having 2m 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 ε-caprolactone, click chemistry, and the ROP of γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA). The linear hydroxyl-terminated PCL (PCL-OH) was synthesized by controlled ROP of ε-caprolactone and then transformed into clickable azide-terminated PCL (PCL-N3). The PCL-N3 precursor was further click conjugated with propargyl focal point PAMAM-typed dendrons (i.e., Dm having 2m primary amine groups) to generate PCL-dendrons (PCL-Dm) using CuBr/PMDETA as catalyst in dimethylformamide solution at 35 °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.