Chain‐coupling reaction of amine‐terminated oligomers by bis(4‐monosubstituted‐5(4 H )oxazolinones)

Bis(5(4H)oxazolinones) derived from naturally occurring α-amino acids were reacted with amine-terminated polyethers and polyamides in the bulk at 175–200°C. Model reactions were also carried out using primary alkylamines. The reactions were studied by means of SEC, and 1H and 13C NMR, and the resulting polymers were characterized by DSC and TGA. The chain-coupling reaction is extremely fast and yields high molar mass copolymers containing peptide linkages in less than 5 min. The NMR spectra of model compounds and polymers were fully assigned, showing that the oxazolinone/amine polyaddition reaction proceeds in the expected way, without any noticeable side reaction. The polymers exhibit lower crystallinity, higher Tg and a melting temperature close to or lower than that of the starting oligomers.