Columnar Liquid Crystals in Polypeptides, 1 Columnar Hexagonal Phase Observed in Lyotropic Solutions of Poly(7-octadecyl-L-glutamate) Dissolved in Amphiphilic Solvents, Such as Octadecylamine, Octadecyi Alcohol, and Octadecanoic Acid

摘要

Poly(γ-octadecyl-L-glutamate) with an a-helical rod surrounded by aliphatic side chains can form a lyotropic columnar hexagonal phase when dissolved in amphiphilic solvents, such as octadecylamine, octadecanoic acid, and octadecanol. This novel liquid-crystalline phase is formed in a polymer concentration region of 50 to 82.5 wt.-% and transforms into the well-known cholesteric phase on heating. The column is composed of a complex of the a-helical polymer with the corresponding amount of amphiphilic solvent, and packed laterally into a two-dimensional hexagonal lattice. The homogeneity of the solutions is ensured by the complete miscibility of the octadecyl groups in both the polymer and the solvent, but in this particular case the polar head groups of the solvent are compartmentalized out of the aliphatic domain composed of octadecyl groups. Such a segregated structure attaches the nature of a rod-like column or micelle to each polymer and stabilizes the columnar hexagonal phase. In contrast to the amphiphilic solvent system, the polymers dissolved in a simple octadecane show the usual phase behavior including only the cholesteric mesophase.