Synthesis and Properties of Thermotropic Compounds with Two Terminal Mesogenic Units and a Central Spacer (Ⅱ). Homologous Series of $\alpha,\;\omega$-Bis (4-p-substituted phenoxycarbonyl)phenoxyalkanes

Two series of thermotropic compounds were prepared and their thermal and liquid crystal properties were examined by differential scanning calorimetry and on the hot-stage of a cross-polarizing microscope. The first series of the compounds has two terminal mesogenic units based on unsubstituted and substituted p-(phenoxycarbonyl) phenyl ethers bracketing a central decamethylene spacer, and the second has 4-(p-phenylphenoxycarbonyl) phenyl ether moiety as the two terminal mesogenic units and central polymethylene spacers of varying lengths. A thermodynamic analysis of the phase transitions was made and explained in relation to structures and thermotropic behavior of the compounds.