Hierarchical self-assembly and secondary structures of linear polypeptides graft onto POSS in the side chain through click chemistry

Abstract

In this study, we used click chemistry to synthesize a new macromolecular self-assembling building block, linear polypeptide-g-polyhedral oligomeric silsesquioxane (POSS) copolymers, from a mono-azido-functionalized POSS (N₃-POSS) and several poly(γ-propargyl-L-glutamate) (PPLG) oligomers. The incorporation of the POSS unit on the side chain of the PPLG moiety enhanced the α-helical conformation in the solid state, as determined by Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance and wide-angle X-ray diffraction analysis. PPLG-g-POSS underwent hierarchical self-assembly, which was characterized using small-angle X-ray scattering and wide-angle X-ray diffraction analyses, to form a hexagonal cylinder packing nanostructure featuring α-helical conformations and POSS aggregates. The attachment of POSS onto the side chain of PPLG could stabilize the α-helical secondary structure with an increase in temperature, compared with pure PPLG by temperature-dependent FTIR analyses.