New 2,2'‐Substituted 6,6'‐Dimethylbiphenyl Derivatives Inducing Strong Helical Twisting Power in Liquid Crystals

Abstract New optically active tetra‐ ortho ‐substituted biphenyl chiral dopants for nematic liquid crystals are described. It was shown, with respect to our previous results, that biphenyl chiral dopants bearing only mesogenic residues on their 2,2'‐positions and without any substituents on their 4,4'‐positions gave rise to very high twisting powers in nematic liquid crystals. This powerful and unconventional chiral dopant molecular architecture allowed the design of new tetra‐ ortho ‐substituted biphenyl derivatives, easier to prepare in optically active form. This simplification of the molecular architecture still affords chiral dopants for nematic liquid crystals with large helical twisting powers and allows more economical large‐scale preparation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)