Refractive Indices of a Methylstilbene Polymer Liquid Crystal

The refractive indices of a side-chain polymer liquid crystal, 4-ω-hydroxyhexyl-l-oxy-)-4'-methoxy-α- methylstilbene, polymethacrylate with weight-averaged molecular weight Mw = 54,000 have been measured as a function of temperature using a Jelley-Leitz refractometer. In these measurements the polymer was aligned by shear flow in the nematic phase. We developed a model for this alignment in order to interpret the data in terms of the polarization direction of the refracted light. The results suggest that the polymer is aligned so that one of its minor optical axes (i.e., one of the directions along which one measures the ordinary refractive index) lies along the flow direction and its principal optical axis (i.e., the direction along which one measures the extraordinary refractive index) is distributed in a plane perpendicular to the flow axis.