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Infrared studies of stereoregularity of copoly(γ‐benzyl‐D,L‐glutamate) by the polymerization of the N‐carboxylic anhydride

The D and L copolymerizations of γ‐benzyl glutamate N‐carboxylic anhydride (NCA) were carried out by two different initiators, n‐butylamine and sodium methoxide. The stereoregularity of the polymer was examined by infrared spectroscopy in the region 700–200 cm−1. A remarkable difference was found between the polymers obtained by these initiators in the region 450–400 cm−1. In the polymer obtained with sodium methoxide as initiator, the 409‐cm−1 peak assigned to local α‐helical conformation was not greatly affected by the amount of the L‐form, but in the polymer obtained by n‐butylamine this peak was much affected by the variation of L‐content. This indicates that the stereo‐selectivity of the polymerization in the sodium methoxide initiated system is higher than that in the n‐butylamine initiated system.