Orientational Order of α-Helical Poly (γ-Benzyl L-Glutamate) in the Lyotrao-Phiecl Ilciaqlu Idp Oclryy(yS-Tbaelnlziynle Ls-Tate and Conformation of the Pendant Side Chain

ABSTRACTDeuterium NMR studies have been performed on variously labeled PBLG samples in the lyotroplc liquid crystalline state. The orientational orders S of the a-helical backbone were estimated from the observed quadrupolar splittings ∆v of the N-D and Cα-D bond. The values of S decrease gradually by dilution until the upper equilibrium concentration (B-point) is reached. The concentration dependence of Scrit has been compared with those derived from standard theories. The relatlve orientation of side chains with respect to the backbone was elucidated by the rotational isomeric state analysis of the ∆v/S data observed for the γ-, γ-, and ζ-methylene, and p-benzyl deuterons. The results indicate that the steric overlaps between adjacent side chains play an important role in determining the preference of conformations in the PBLG system. A similar analysis has been extended to poly(L-glutamic acid) esters carrying a homologous series of ester residues, -C(O)O(CH2)nC6D5 with n = 2 and 3. A distinct odd-even oscillation was observed for the orientation of the terminal phenyl groups with n.