Synthesis, characterization, conformation and self-assembly behavior of polypeptide-based brush with oligo (ethylene glycol) side chains

• A polypeptide-based brush composed of polypeptide backbone and oligo (ethylene glycol) side chains was effectively synthesized.
• The α-helix of the polypeptides showed reversible changes upon heating in water.
• The self-assembly micelles formed by the brush is thermo-sensitive in water.

A new polypeptide-based copolymer brush composed of poly (γ-propargyl-L-glutamate)-block-poly (propylene oxide)-block-poly (γ-propargyl-L-glutamate) backbone (PPLG-b-PPO-b-PPLG) and oligo (ethylene glycol) (PEG) side-chain was synthesized by combination of N-carboxyanhydride ring-opening polymerization and click chemistry. Nearly 100% grafting efficiency was achieved by copper-catalyzed azide-alkyne Huisgen 1,3-dipolar cycloaddition (CuAAc) reaction. The α-helical conformation adopted by the grafted polypeptide blocks in water was relatively stable and showed a reversible change in a heating–cooling circle from 5 to 70 °C. It displayed weak stability against elevated temperature but still reversible changes in the presence of 0.47 M NaCl. The brushes were amphiphilic and could self-assemble into thermo-sensitive micelles in water. Big micelles could break into small micelles upon heating due to the improved solubility.

The conformation dependance of polypeptide blocks on temperature.Figure optionsDownload as PowerPoint slide