Nanodomain-induced chain folding in poly(gamma-benzyl-L-glutamate)-b-polyglycine diblock copolymers

We report on the self-assembly mechanism and dynamics in a series of poly(gamma-benzyl-l-glutamate)-b-poly(glycine) (PBLG-b-PGly) diblock copolymers within the composition range 0.67 < or = f(PBLG) < or = 0.97 and the temperature (T) range 303 < T < 433 K. Small- and wide-angle X-ray scattering, (13)C NMR, and differential scanning calorimetry are used for the structure investigation coupled with dielectric spectroscopy for both the peptide secondary structure and the associated dynamics. These techniques provide not only the nanophase morphology but also the type and persistence of peptide secondary structures. The thermodynamic confinement of the blocks within the nanodomains and the disparity in their packing efficiency results in multiple chain folding of the PGly secondary structure that effectively stabilize a lamellar morphology for high f(PBLG). Nanoscale confinement proves to be important in controlling the persistence length of secondary peptide motifs.