ODD-EVEN EFFECTS IN THE OPTICAL-PROPERTIES OF CHIRAL TRIPLET LIQUID-CRYSTALS BASED ON ESTRADIOL

A series of bis omega-cyanobiphenylyloxyalkanoate esters of estradiol with variable spacers have been prepared as chiral triplet liquid crys tals. The compounds show very broad cholesteric phases and are transfo rmed into cholesteric glasses at room temperature. They exhibit a rela tively weak odd-even effect with spacer length for their cholesteric-i sotropic transition temperatures and the associated entropy changes. T his weak odd-even effect probably results from the orientation of the ester linkages to the estradiol moiety. This causes the cyanobiphenyl groups to be poorly ordered with respect to one another, regardless of the odd or even number of methylene units in the alkanoate spacer. Th e selective reflection wavelength of the planar cholesteric phase of m ost of the compounds increases strongly with temperature and changes f rom blue at low temperature to red at high temperature. An odd-even ef fect of the selective reflection wavelength with spacer length as obse rved with other chiral twin and triplet liquid crystals is hardly obse rved.