Structural Aspects and Host Effects of the Chirality Transfer by Mesogenic Substituted Aminoalcohols

ABSTRACT

In continuation of the investigations on chiral dopants derived from the aminoalcohols ephedrine and pseudoephedrine as chiral bivalent structure elements, a series of new agents bearing very different substituents has been synthesized. The products turned out to be suited for preparation of short-pitch chiral liquid crystalline (LC) phases and were characterized by measuring their helical twisting power (HTP) in nematic host mixtures. In particular cases, structural features on the molecular level of dopants in relation to host constitution will be discussed. On the other hand, macroscopic properties, such as dynamic and dielectric data of achiral host systems, have been considered to find out practically useful guidelines for tailoring chiral LC guest–host systems. The studies include recording of nuclear magnetic resonance (NMR) spectra to study the dependence of helicity induction on the configuration of stereogenic center. Further, some photostability tests of cholesteric mixtures reflecting light in the visible range have been undertaken with regard to exploiting these dopants in electro-optic liquid crystal devices such as cholesteric bistable displays.

KEYWORDS:

• Chiral aminoalcohols
• dielectric spectroscopy
• dynamic properties
• NMR
• photostability

Acknowledgments

We are indebted to R. Stannarius (Magdeburg), H. Kresse (Halle), and M. Gwiazda (Teltow) for many useful hints and discussions. The authors also thank A. Fujita (JNC Co.) for supplying LC material.

Funding

Financial support by the German Federal Ministry of Economics and Technology within the aeronautical research project “INGA – Innovative Galley” (20K1103D) is highly acknowledged.