| Research Abstract |
Thermotropic liquid crystal polymers, R_1,R_2,R_3, and R_4, which contain a phenyl group in the main chain, have a rigid backbone and in their side chains a low molecular weight liquid crystal is incorporated. At the end of their side chains a flexible alkoxy group -O(CH_2)_5-CH_3 is attached to realize liquid crystalline states by reducing their melting points. The purpose of the present study was to explore the relation between the structure and the liquid crystallinity of the four kinds of liquid crystalline polymers, R_1,R_2,R_3,R_4 by using two-dimensional infrared spectroscopy and x-ray diffraction correlation spectroscopy.
First of all, the phase transition temperatures of R_1,R_2,R_3, and R_4 were determined by measuring differential scanning calorimetry (DSC) and polarized microscopy. It was found from x-ray diffraction patterns that R_1,R_2,R_3, and R_4 are nematic liquid crystals and that not only the mesogen but also the main chain are oriented with the side chains being fitted inside the other. The orientation is not two dimensional but three dimensional. it is not simple one but complicated one. The DSC results revealed that R_1,R_2,R_3, and R_4 are not pure nematic liquid crystal but partly smetic liquid crystal. It was found from temperature-dependent infrared spectroscopic study that there are two kinds of C=O groups and conformational change around the C-O bond occurs in the side chain. An asynchronous spectrum calculated from the temperature-dependent infrared spectra of R_1,R_2,R_3, and R_4 elucidated that the side chain is oriented at higher temperature than the main chain. This result was also confirmed by the temperature-dependent x-ray diffraction measurements.
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