Synthesis of well-defined polypeptide-based diblock copolymers

We report an efficient protocol to synthesize rod-coil diblock copolymers of an α-helical polypeptide and poly(4-vinyl pyridine) via a combination of “living” ring-opening polymerization of α-amino acid N-carboxyanhydrides at 0 °C, polymer end-group modification and atom transfer radical polymerization (ATRP) of 4-vinyl pyridine (4-VP). Due to the competent effect of the pyridine groups with the ATRP ligand and the low initiation efficacy of the rigid polypeptide macroinitiator at mild temperatures, the challenge on ATRP of 4-VP was overcome by performing the ATRP process at 100 °C. Relatively well-defined poly(γ-benzyl L-glutamate)-b-poly(4-vinyl pyridine) diblock copolymers were successfully synthesized and characterized. Upon solvent vapor annealing, thin films of the diblock copolymers showed micro-phase separation behavior.