Synthesis of amphiphilic polyethylene-b-poly(l-glutamate) block copolymers with vastly different solubilities and their stimuli-responsive polymeric micelles in aqueous solution

This paper describes the synthesis, characterization, and self-assembly behavior of amphiphilic polyethylene-block-poly(l-glutamate) (PE-b-PGA) diblock copolymers. PE-b-PGA diblock copolymers were obtained by ring-opening polymerization (ROP) of γ-benzyl-l-glutamate-N-carboxyanhydride (BLG-NCA) using PE–COOCH(iPr)NH2 as a macroinitiator and subsequent deprotection of the benzylester groups. The self-assembly behaviors of the PE-b-PGA copolymers in water were studied as a function of pH and ionic strength by means of fluorescence spectroscopy, laser light scattering, UV-circular dichroism, and transmission electron microscopy. The size of the polymeric micelles decreases with a decreasing pH value even at high salt concentrations because the solvating PGA units can perform a coil-to-helix transition.