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

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.