Influence of the position and number of fluorine atoms and of the chiral moiety on a newly synthesized series with anticlinic properties

A series of trifluoro-substituted benzoate derivatives: (S)-1-ethylheptyl 4-[4-(4-alkyloxy-3- fluorobenzoyloxy)-3-fluorobenzoyloxy]-2-fluorobenzoates is reported. The short chain members (n = 8 to n = 11) display a direct SmC*A-SmA transition, whereas for longer chains a SmC* phase appears, but no ferrielectric phases are present, and a direct SmCA*-SmC* transition is obtained. The mesomorphic properties were studied by optical microscopy and DSC, and by electro-optical, helical pitch and optical rotatory power measurements. The effect of the number and position of the fluoro substituents, and the influence of the chiral moiety on the mesomorphic behaviour are discussed.