A light scattering study of orientation of liquid–crystalline rodlike textures of poly(γ-benzyl-L-glutamate) in an electric field perpendicular to the direction of sample cell surface by means of saturation electric birefringence method. III

Abstract

The orientation behavior of liquid crystalline solutions of poly(γ-benzyl-L-glutamate) (PBLG) in chloroform was investigated with respect to characteristic electro-optical properties of macromolecules using polarizing microscope and small angle light scattering techniques, when an electric field was applied parallel to an incident beam. The birefringence phase exhibited an irregular patchwork of predominantly blue, yellow, and pink regions under cross polars without applying the electric field and the corresponding Hv light scattering was circular. When the field was applied, the brightness of the phase decreased with increasing voltage and the corresponding Hv patterns became a typical X-type characterizing the scattering from rodlike textures. The analysis was made for a model system. In this model system, rods orient randomly in the three-dimensional space in the absence of the electric field, whereas when the electric field is applied, the rods orient predominantly parallel to the electric field. The orientation distribution function of the rods was assumed to be the steady-state orientation distribution function of macromolecules under an electric field which was proposed to investigate electric properties of a dilute solution of rigid macromolecules by O’Konski et al. Thus, the light scattering patterns were calculated as a function of an electric field strength. The calculated results were found to be rather close to the observed ones with a proper choice of parameter associated with the magnitude of the disorder of the optical axes.