| Summary: | 碩士 === 國立中央大學 === 化學研究所 === 92 === Abstract
A novel system of symmetric and non-symmetric dimers containing benzoxazole units through ester linkages to the terminal chains have been synthesized and investigated for their thermal behaviour. The mesomorphic behaviour of these compounds was characterised by polarised optical microscopy, differential scanning calorimetry and powder X-ray diffraction. All symmetric dimers linked by a methylene spacer -(CH2)n containing from n = 5 to n = 11 exhibited nematic phase (N) or smectic A phase (SmA). The temperature range of smectic A phase increased with terminal carbon chain length, and decreased with the carbon length of the spacer. The structure of the smectic A phase was confirmed by powder X-ray diffraction, and the data also indicated that the symmetric dimers were in fact arranged by monolayers and not intercalated. In these dimers, the spacer length has a remarkable influence on the thermal behaviour.
A series of palladium(II) complexes derived from 4-dodecyloxy phenyl-2-carboxylic acid-4-[(3,4-didodecyloxyphenylimino)methyl]-3- hydroxyphenylester was prepared and characterized. Liquid crystalline properties of these palladium (II) complexes were studied and investigated by differential scanning calorimeter (DSC) and polarized optical microscopy (POM). The structures of the mesophases for palladium (II) complexes were also characterized and confirmed as nematic phase or smectic C phase depending on the terminal chains. The formation of mesophases was sensitive to the numbers of the alkoxy side chains and the carbon length of the side chains. The crystal and molecular structures of the complex were determined by means of x-ray analysis. The complex was crystallizes in the triclinic space group P1.
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