Synthesis, Characterization And Properties Of 4-Cyano-3-Fluoro-Phenly Ester

In this study, three new series of esters containing fluorine atom have been synthesized using 2-fluoro-4-hydroxybenzonitrile, 3-(4-hydroxy-phenyl)-acrylic acid, 4 -hydroxy-bipheny-4-carboxylic acid, 3-(4-hydroxy-3-methoxy-phenyl)-acrylic acid and halohydrocarbons as raw materials through etherificaion and esterification. These esters were p-substituted cinnamic acid esters (series I), 3-(4-alkyloxy-3-methoxy-phenyl) acrylic acid esters (series II) and 4 -alkyloxy-bipheny-4-carboylic esters (series III). Their structures were determined with ¹H nuclear magnetic resonance (¹H NMR) and infrared spectra (IR). The liquid-crystalline behaviors of these compounds were also investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM).It was found in this study that:(1) In series I, 16 new cinnamic acid esters were synthesized, and 11 of them exhibited liquid-crystalline properties. When there are electron-withdrawing groups (-F, -Cl or -NO₂) substitute on the 4-position of benzene ring or when the alkoxyl group on the benzene ring of cinnamic acid ester is small, such as in the case of methoxyl or ethoxyl, the compound did not exhibit liquid-crystalline properties. With the increasing number of carbons (n>2, except for n=9) in the alkoxyl group on the benzene ring of cinnamic acid ester, these compounds exhibited mesophases. At the same time, the relationship between the number of carbon atoms in the alkoxyl chain and the transition temperatures, as well as the relationship between the number of carbon atoms in the alkoxyl chain and the nematic range have been studied. It was shown that the melting points and the clearing points decreased as the n increases firstly (when n<6), but the nematic range increased. The melting points and the clearing points...