Chromatographic fractionation of primary amine initiated poly‐γ‐benzyl‐L‐glutamate

The S CHULZ theory on the chromatographic fractionation with a B AKER and W ILLIAMS column was applied to the system poly‐γ‐benzyl‐L‐glutamate/methanol/methylenechloride. It was found that the separation is very efficient if the fractionation conditions are carefully selected. Moreover the results are in good agreement with the suggested mechanism of N‐carboxyanhydride (NCA) polymerization initiated by primary amines. In fact from the fractionation data it was found that the number average degree of polymerization P̄ n is approximatively equal to the ratio between the initial concentrations of monomer and initiator ([M] 0 /[I] 0 ). A very large inhomogeneity was found with P̄ w /P̄ n ≃ 7, in agreement with previous literature data 1 .