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.