High‐molecular‐weight poly(amino acid)s by the direct polycondensation reaction promoted by triphenyl phosphite and LiCl in the presence of polyvinylpyrrolidone

Poly(α‐amino acid)s of high molecular weight were obtained by the direct polycondensation reaction of α‐amino acids in the presence of polyvinylpyrrolidone (PVP) as a matrix of triphenyl phosphite and LiCl in N‐methylpyrrolidone (NMP). Molecular weights of the polymer produced were improved by use of an increasing amount of matrix of higher molecular weight. Most favorable results were obtained by the reaction at 80°C for 16 hr at a monomer concentration of 0.33 mole/liter in a NMP solution that contained about 3 wt % LiCl in the presence of an equivalent unit mole of PVP with the molecular weight of 3.6 x 105. The polymer from β‐alanine with high molecular weight, which is difficult to obtain by the NCA method, was easily prepared by this process.