摘要： In this paper we report on the design, synthesis and characterisation of two new ferroelectric liquid crystalline compounds based on using cores of (i) 5-phenyl-pyrimidine benzene and (ii) 5-phenyl-pyrimidine benzoate terminated by achiral trisiloxane chain, and chiral (S) alkyl chain on the opposite ends of their respective mesogens. These compounds exhibit broad temperature ranges of SmA* and SmC* phases, whereas the latter exists at room temperature down to 11 oC. This is one of the desirable features of the compounds for perspective applications in devices. In both compounds, the differential scanning calorimetry shows a weak first order SmA*-SmC* transition. This observation is supported by determining the critical exponent of the power law as ~0.2 that describes the dependence of the tilt angle and the spontaneous polarization on temperature. The two compounds show excellent de Vries characteristics in terms of the layer shrinkage in SmC*, the maximum shrinkage in both cases is ~ 1.5%. Furthermore (i) the birefringence decreases with a reduction in temperature instead of increasing in SmA*, and (ii) a large field-induced birefringence is observed in SmA* close to the SmA*-SmC* transition temperature, (iii) the maximum birefringence measured is much lower than of a typical FLC material. The characteristics of these compounds when compared to a conventional/typical ferroelectric liquid crystalline mixture show that these materials surpass in performance in terms of having a (i) wider temperature range of both SmA* and SmC* phases and (ii) higher switching speed. The layer thickness in SmA* and SmC* is measured using the techniques of (a) small-angle X ray diffraction, and the (b) optical interferometry of free standing smectic films. A comparison of the results is used to determine an exceptionally useful result of the apparent tilt angle as a function of temperature in SmA* without the need of applying the electric field across the cell.