Fluorine containing chiral synthons for ferro and antiferroelectric liquid crystal compounds and their application

Abstract

Recently, the high performance and functional properties of the fluorine containing organic compounds are focussed in order to develop the organic functional materials in a wide research area of material science. Especially the chiral fluorine compounds are being utilized as the building block in many research fields such as agrochemicals, pharmaceuticals, LB films and liquid crystals. Recently, we have successfully synthesized novel fluorine containing antiferroelectric liquid crystal compounds which displayed new phenomenon ‘Tristable State’ switching from its new smectic phase (SmCA*). These liquid crystal compounds either alone or in a mixture attribute the wide antiferroelectric smectic phase, sharp DC threshold and characteristic hysteresis of the threshold voltage. The purpose of this study is to synthesize fluorine containing chiral synthons having CH 2F, CHF 2, CF 3 and C 2F 5 group directly linked to the chiral center of the novel antiferroelectric liquid crystal compounds. The effect of fluorine substituents at the chiral center was also evaluated with special interest on the appearance of tristability in optoelectronic application. They are explained briefly as follows; ▪ 1. Appearance of Tristability It is interesting to note that the CF 3 and C 2F 5 substituents, linked to the chiral center of molecular structures showed antiferroelectricity, whereas groups such as CH 2F and CHF 2 substituted at chiral center exhibited the ferroelectricity. 2. Opto-electronic Properties The ferro and antiferroelectricity are characterized by their single and double hysteresis loop which is really obtained by introducing ferro and antiferroelectric liquid crystal compounds in between the device cell and by applying the triangular wave voltage. The CF 3 and C 2F 5 substituents at chiral center of liquid crystal compounds displayed double hysteresis loop (Fig. 1), whereas chiral center of the compounds substituted by CHF 2 or CH 2F group exhibited the single hysteresis loop and correspond to the ferroelectricity. A prototype antiferroelectric liquid crystal display have been demonstrated at SAMPE 1989 Japan. ▪