Dimer liquid crystals with bent mesogenic units

Three series of dimer liquid crystals containing an aromatic and a choleste ryl mesogenic unit were synthesized and investigated The compounds within t he series differ in the length of the spacer connecting the mesogenic group s. Two of the three series contain an aromatic mesogenic group that is conn ected to the spacer at a meta-position instead of the para-position. Due to the presence of this bent mesogenic group, the odd-even effect in the tran sitional properties that is normally observed for dimer liquid crystals is reversed as compared with that of the third series, which contains a para-s ubstituted aromatic mesogenic group. The reversed odd-even effect is found for the isotropization temperatures, the associated enthalpy changes and al so for the optical properties.