Electroclinic Effect In Unsymmetrical Dimeric Liquid Crystals Composed of Two Non-Identical Chiral Mesogenic Entities

We report the synthesis and physical characterization of two unsymmetrical dimeric liquid crystals containing two different chiral mesogenic segments, namely, a tolan unit with (S)-2-octyloxy tail and a cholesteryl ester unit which are separated by a n-butyl (even) and n-pentyl (odd) spacers respectively. Both the dimers exhibit a smectic A mesophase, with the dimer having the n-pentyl spacer stabilizing this phase over a temperature range of ˜150°. Electro-optic studies performed on this compound show that it exhibits an observable electroclinic effect over this entire temperature range. At room temperature, the electroclinic tilt angle and the response time observed are comparable to those exhibited by some monomeric materials.