In order to examine the effect of the glycyl residues the stability of the α-helix, a series of blockpolypeptides containing ordered sequences of L-alanine and glycine residue were synthesized by heterogeneous polymerization of their N-carboxyanhydrides (NCA) in acetonitrile as p-phenylenediamine initiator with two functional groups. These molecular conformations were investigated by optical rotatory dispersion of dilute solution in dichloroacetic acid (DCA : helix solvent), and in trifluoroacetic acid (TFA : random coil solvent) and chloroform (CHCl₃ : helix solvent) mixtures. The results indicated that the glycyl residues reduced the stability of the α-helix and the order of the stability of the α-helix of these blockpolypeptides were found to be: (Ala)-(Gly)-(Ala)>(Ala)-(Gly)>(Ala)-(Gly)-(Ala)-(Gly)>(Gly)-(Ala)-(Gly)