DETERMINATION OF ORIENTATION IN THERMOTROPIC LIQUID-CRYSTALLINE POLYMER-FILMS BY SPECTROGRAPHIC MEASUREMENT OF THE BIREFRINGENCE

The degree of orientation in thermotropic liquid crystalline polymer f ilms has been determined as a function of the draw ratio using a speci ally developed spectrographic birefringence technique, diffuse reflect ance infrared spectroscopy (DRIFT), and wild-angle X-ray scattering (W AXS). Quantitative measurements of the average birefringence were obta ined despite the huge turbidity of the samples. The order parameter ca lculated from the birefringence was found to depend on the draw ratio according to the Kuhn and Grun equation for pseudo-affine deformation. The infrared dichroism was measured as a function of film thickness b y layer removal. The thickness-averaged orientation calculated from th e DRIFT measurements also indicated affine deformation of the films. T he orientation derived from WAXS appeared to be clearly overaffine. Th e difference between the results from WAXS and the results from the ot her two techniques is attributed to preferential orientation of the cr ystalline fraction due to flow-induced crystallization in the films wh ich is detected only by WAXS.