X-ray Diffraction Patterns of Liquid Crystalline Solutions of Poly-γ-benzyl-L-glutamate

Abstract

THE X-ray diffraction patterns of liquid crystalline solutions of poly-γ-benzyl-L-glutamate in various solvents have been observed by Luzzati et al.¹ for a range of concentrations. They report four phases, namely, isotropic, cholesteric, paracrystalline and complex; the patterns are observed with unoriented materials and reflexions corresponding to equatorial reflexions only are recorded. In some cases, several reflexions are observed which apparently index on a hexagonal lattice. In the cholesteric phase, observed in m-cresol at concentrations between about 20–36 parts by weight of polymer per 100 parts of solution, one diffuse reflexion only is seen. Luzzati et al. calculate the length of the residue translation h of the polypeptide chain assuming that this diffuse reflexion may be regarded as the 10 reflexion of a hexagonal net and (implicitly) that the whole of the polymer has the corresponding mean inter-chain distance. For the cholesteric phase in m-cresol they obtain a value ∼2.0 Å for the residue translation h and suggest that this is evidence that the chain conformation is the 3₁₀ helix (for which h is 2.0 Å).