Using Hydrogen-Bonding Interactions To Control the Peptide Secondary Structures and Miscibility Behavior of Poly(l-glutamate)s with Phenolic Resin

Abstract

We synthesized three low-molecular-weight poly(glutamate)s—poly(γ-methyl l-glutamate) (PMLG), poly(γ-ethyl l-glutamate) (PELG), and poly(γ-benzyl l-glutamate) (PBLG)—through living ring-opening polymerization of their α-amino acid-N-carboxyanhydride derivatives and then blended them with phenolic resin to control the secondary structures of these polypeptides. Each of the three binary blends exhibited a single glass transition temperature (differential scanning calorimetry) and a single-exponential decay of proton spin–lattice relaxation times in the rotating frame [T1ρH; solid state nuclear magnetic resonance (NMR) spectroscopy], characteristic of a miscible system. The strength of the interassociative interactions depended on the nature of the hydrogen bond acceptor groups, increasing in the order phenolic/PELG > phenolic/PMLG > phenolic/PBLG, as evidenced through analyses using Fourier transform infrared (FTIR) spectroscopy and the Painter–Coleman association model. The fractions of α-helical conformat...