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 (gamma-propargyl-L-glutamate)-block-poly (propylene oxide)-block-poly (gamma-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 azidealkyne Huisgen 1,3-dipolar cycloaddition (CuAAc) reaction. The alpha-helical conformation adopted by the grafted polypeptide blocks in water was relatively stable and showed a reversible change in a heatingcooling circle from 5 to 70 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.