The development of LC monophenyl unit is of a great interest for reach low cost LC materials. The aim of this work was to demonstrate the possibility to obtain monomer incorporating single phenyl unit for LC field. We report the synthesis and the characterization of acrylic monomers in fluorinated series which differ by the lengthening of the hydrocarbon spacer linking the acrylic part to the "mesogenic" core. LC behaviour was determined by DSC and POM apparatus. The increasing of the length of this hydrocarbon spacer dramatically decreases the span of the mesophase of type smectic. For a long spacer no mesomorphism is observed.