Synthetic oligopeptides as polymer precursors

By reacting N-carboxyanhydrides of L-phenylalanine, DL-phenylalanine, L-leucine or of a mixture of DL-phenylalanine and L-leucine with hexamethylenediamine (15-20 mol.% related to monomer) in absolute benzene at 25 °C, which was followed by an additional treatment with hexamethylenediamine (60 °C, 4 h), oligopeptides were prepared with the average functionality (Fn) 1.72-1.96 with respect to primary amino groups. The reaction between these oligopeptides and poly(oxyethylene) terminated with isocyanate groups (Fn 1.69-1.94) in anhydrous chloroform at 25 °C leads to copolymers of the type A-B and A-B-A with a minority content of copolymers (A-B)m for m ≥ 2. The low efficiency of the coupling reaction is attributed to the formation of an important amount of monofunctional oligopeptide in the preparation reaction.