NEXAFS Determina\-tions of ``Skin'' Orient\-a\-tion of Injection-Molded Thermotropic Liquid Crystalline Copolyesters

Near edge X-ray adsorption fine structure (NEXAFS) spectroscopy is being used to characterize anisotropy in injection-molded plaques fabricated from thermotropic liquid crystalline copolyester polymers (TLCPs). [1] NEXAFS is sensitive to the orientation of the molecular pi orbital of backbone phenyl groups of the top 3 nm of a surface via the variation in intensity of the partial electron yield of Auger electrons of the 1s $\to \quad \pi $* transition of the C=C bonds within the C K edge spectrum. Plaques of various commercial TLC polymers were injection-molded under controlled conditions and comparisons relative to mold and melt temperatures, injection speed, and polymer type were made. Good agreements were obtained between the results via 2-D wide-angle X-ray scattering in transmission and NEXAFS for appropriate processing conditions that resulted in near identical skin and core orientation. [1] R. A. Bubeck et al., \textit{J. Appl. Polym. Sci.}, submitted November, 2004.