Three series of symmetrical dimer liquid crystals, i.e. bis(dodecyloxybenzoyloxybenzoyloxy)alkanes (BC12) and bis(dodecyloxy- and hexadecyloxybenzoyloxyphenyl) alkanedicarboxylates (QC12 and QC16) with a spacer ranging from, two to eight methylene units, have been synthesized and their thermotropic properties were characterized. The isotropization temperatures show a pronounced odd - even effect as a function of the parity of the spacers. Most compounds exhibit a SmC mesophase. The QC12 and QC16 compounds, with on eight methylene spacer, possess an additional low temperature tilled SmI or SmF mesophase. Changing the orientation of the ester group as in the BC12 series results in a dramatic change of the thermotropic behavior.
- alkylene spacer