Conformational transition of nanoparticles composed of poly(γ-benzyl L- glutamate) as the core and poly(ethylene oxide) as the shell

Diblock copolymers composed of poly(γ-benzyl L-glutamate) (PBLG) as the hydrophobic component and poly(ethylene oxide) (PEO) as the hydrophilic component were obtained by the polymerization of γ-benzyl L-glutamate N-carboxyanhydride, initiated by the primary amino end group of the α-methoxy-ω-amino PEO. Nanoparticles are formed from an organic solution of the block copolymers by the diafiltration method. From the NMR measurement of the nanoparticle in water, the PEO segments in the copolymer extend out as the shell from the nanoparticle core into the aqueous environment. From circular dichroism measurements in ethylene dichloride solution, it was found that the polypeptide block exists in the α-helical conformation and adopts right-handed helix sense, as in PBLG homopolymer. However, the helix sense of PBLG in the copolymer nanoparticles prepared from organic solvent depends on the PEO content in the copolymer and the nature of solvent.