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Several series of new asymmetric and fluorinated triphenyl-diacetylenes are synthesized and characterized. These synthesized compounds which exhibit respectively a wider temperature range of mesohase, and a small melting enthalpy are suitable for formulating LC eutectic mixtures.
The first pat of this thesis described the synthesis and characterization of a series of compounds containing asymmatric alkyl terminal groups. 4-lodotoluidine was coupled with 4-alkylphenylacetylene, followed by diazotization and iodination to forma 4-[2-(4-alkylphenyl)-1-ethynyl]-2-iodotoluene which was further coupled with 4- alkyl-phenylacetylene to yield the asymmetric triphenyl-diacetylene compounde. All the obtained compounds exhibit respectively a nematic phase. Their clear temperatures decrease with increasing the length of alkyl groups. The results demonstrate that introducing an lateral methyl group into the mesogemic core decreases dramatically the melting points of teh obtained compounds and also increases their temrperature range of the nematic phase. Furthermore, the chain lengths of two terminal alkyl groups located at each side of mesogenic core have profound effect on the melting points of the obtained compounds.
The synthesis and characterization of a series of fluorinated triphenyldiaceylenes were described in the second part of this study. All obtained compounds reveals respectively a nematic phase. Their melting points decrease as the terminal alkyl chain length increase. However, the melting enthalpies of this serise of the compounds are larger than those of previous series of compounds. In this study, the detailed structure-properties relationship of the obtained compounds is discussed.
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