Synthesis of poly(2-ethyl-2-oxazoline)- block-polypeptide copolymers by combination of ring-opening polymerization of oxazoline and polycondensation of activated urethane derivatives of α-amino acids

摘要

In this study, we examined the utilization of a primary-amine-terminated poly(2-ethyl-2-oxazoline) as macroinitiators for the chain-growth polycondensation of activated urethane derivatives of α-amino acids to obtain poly(2-ethyl-2-oxazoline)- block -polypeptide diblock copolymers. To incorporate polypeptide segments into the poly(2-ethyl-2-oxazoline), we prepared four N -phenoxycarbonyl derivatives of α-amino acids, namely, Z- l -lysine, l -alanine, l -phenylalanine, and benzyl- l -serine, which were readily synthesized by N -carbamylation of the tetrabutylammonium salts of the α-amino acids with diphenyl carbonate. We demonstrated that poly(2-ethyl-2-oxazoline)s possessing an amino terminal successfully served as initiators for the chain-growth polycondensation of these urethane derivatives; heating at 60?°C in N,N -dimethylacetamide eliminated phenol and CO~(2)to give the corresponding diblock copolymers. The structural and thermal properties of the obtained diblock copolymers were determined by FT-IR,_(1)H NMR, SEC, and TGA.