Multiple Levels of Organization in Amphiphilic Diblock Copolymers Based on Poly(γ-benzyl-l-glutamate) Produced by Aqueous ROPISA.

Abstract

A recent method for producing amphiphilic block copolymers and nano-objects based on the ring-opening polymerization-induced self-assembly (ROPISA) in aqueous buffer is explored with respect to the tunability toward nanostructures. ROPISA gives rise to polypeptide copolymers with unprecedented levels of organization. By employing amphiphilic block copolymers of poly(ethylene glycol) (PEG) with the synthetic polypeptide poly(γ-benzyl-l-glutamate) (PBLG) and a combination of static (¹³C NMR, X-ray scattering, polarizing optical microscopy), thermodynamic (differential scanning calorimetry), and dynamic (dielectric spectroscopy) probes, we demonstrate a record of six levels of organization only found before in natural materials. These levels of organization could not be obtained in earlier morphology investigations of copolymers based on PEG and PBLG prepared by different methods. Furthermore, the type of NCA monomer (BLG-NCA vs Leu-NCA) and the solvent treatment method had an influence on the degree of segregation, the α-helical content, and the order-to-disorder transition temperature in the PEG-b-PBLG and PEG-b-PLeu copolymers.