Hierarchical self-assembly structures of POSS-containing polypeptide block copolymers synthesized using a combination of ATRP, ROP and click chemistry

In this study, we used a combination of atom transfer radical polymerization, ring opening polymerization, and click chemistry to synthesize new organic/inorganic macromolecular self-assembling building blocks of polystyrene-b-poly(γ-propargyl-L-glutamate-g-polyhedral oligomeric silsesquioxane) [PS-b-(PPLG-g-POSS)]. The incorporation of the PS and POSS units enhanced the α-helical conformation in the solid state, as determined using Fourier transform infrared (FTIR) spectroscopy and wide-angle X-ray diffraction (WAXD). Hierarchical self-assembly of the PS-b-(PPLG-g-POSS) diblock copolymers, which we characterized using WAXD, small-angle X-ray scattering, and transmission electron microscopy, led to the formation of cylindrical structures as a result of microphase separation of the diblock copolymer; the hexagonal cylinder packing nanostructure featured α-helical conformations of polypeptide segments, which were oriented perpendicular to the direction of the cylinder column from diblock copolymers; aggregation of the POSS moieties induced the packing into hexagonal lattice structures. The attachment of POSS units onto the side chains of PPLG stabilized the α-helical secondary structures at elevated temperature, relative to those of pure PPLG and PS-b-PPLG, as determined through temperature-dependent FTIR spectroscopic analyses.