New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

New (E)-16-arylidene derivatives of 3 beta-hydroxyandrost-5-en-17-one and their acetates containing different substituents in the arylidene fragment were synthesized. The ability of the synthesized chiral compounds to induce helical supramolecular ordering (their helical twisting power) upon the introduction into the nematic liquid crystal (LC) 4-cyano-4'-pentylbiphenyl (5CB) and into multicomponent mixtures E63 and LC-1289 characterized by a wide mesophase interval. The dependence of the helical twisting power of the studied chiral additives (CAd) on their molecular structure was analyzed. The highest helical twisting power (44.6-67.1 mu m(-1)) was revealed for the synthesized acetates. It was found that the composites based on LC-1289 and E63 containing the studied CAd in very low concentrations (a parts per thousand currency sign10-11 mol.%) have selective light reflection in the visible spectral region. The helical twisting power of the studied alpha,beta-unsaturated ketones is determined by the combined influence of the anisotropy of polarizability of CAd molecules and specific features of their molecular shape.