New Nematic Liquid Crystals: Influence of Rigid Cored, Alkenyl Side-Chains and Polarity on Material and Display Properties

Abstract

From the design of non-polar molecular structures exhibiting different rigid cores and isolated C=C double bonds in different side-chain positions and from investigations into the static dielectric birefringence, viscous, and all three elastic constants k ₁, k ₂, k ₃, new, negative dielectric anisotropic nenatic liqueid crystals result, namely apolar alkenyls, which are shown to cover a wide range of materail porpertie, including large twist constants k ₂. The combination of double bonds in 4-position, with rigid cores comprising heterocyclic rings is shown to lead to exceptionally low elastic rations k ₃/k ₁ ∼ 0.4 with simultaeoulsy low optical anisotropies and low roatational viscosities γ₁. Moreover, laterally substituted alkenyls are shown to exhibit large negative dielectric anisotropies rendering them applicable for low viscous, positive contrasat guest-host mixtures with high order parameters 0.72≤ S ≤ 0.78. The stability of the new nematics comprising isolated double bonds is shown to be comparable to that of satrurated PCHs or biphenyls.