Three Dimensional Orientation Measurements in Liquid-Crystalline Polymers by FT-IR ATR Dichroism

摘要

Fourier transform infrared attenuated total reflecting dichroism technique using double-edged crystal and specially-built attachment was used for a comprehensive characterization of molecular orientation in three dimension on an injection molded liquid crystalline copolyester plaque. This copolymer contains 75% of hydroxybenzoic acid (HBA) and 25% of 2,6-hydroxynaphthoic acid (HNA). Orientation functions were estimated averaging about a 10 u thick layer as a function of the location from the gate as well as the thickness direction. Orientation profiles are similar for both HBA vibrational peak and HNA vibrational peak, which is not inconsistent with the proposed random copolymer structure by x-ray studies. Orientation, however, is found to be a strong function of the location from the gate as well as the thickness direction. In general, greater orientation has been observed on the skin than the intermediate or the core surface, with molecules lying on the surface rather than being tilted along the thickness direction. Keywords: Surface structure, Fourier transform infrared attenuated total reflectance Dichroism, Injection, Molded liquid crystalline polymers, Orientation profile, Molecular orientation.