Factors Affecting Microstructural Scale in Liquid Crystalline Materials

Abstract Light microscopy was used to study the effects of molecular weight and chain flexibility on micro-structural scale in liquid crystalline materials. Studies of poly(p-hydroxybenzoic acid) oligomers show that the scale exhibited by a semiflexible molecule is not sensitive to increasing molecular weight when the contour length exceeds the persistence length. For contour lengths shorter than the persistence length, the microstructural scale is significantly coarser and depends on molecular weight. In the case of linear rigid polytolan oligomers, increasing the molecular axial ratio results in coarser microstructures. Rheinberg differential color contrast is shown to provide an optimum combination of contrast and resolution for highlighting fine-scale orientational defects.