摘要 : Two series of non-symmetric banana-shaped compounds, both with one alkyl and one alkenyl terminal tail, have been synthesized and studied. Both series were compared with the corresponding series with two saturated terminal alkyl t... 展开 Two series of non-symmetric banana-shaped compounds, both with one alkyl and one alkenyl terminal tail, have been synthesized and studied. Both series were compared with the corresponding series with two saturated terminal alkyl tails. All the compounds have a bent central 1,3-phenylene bis(4-benzoyloxy) benzoate core; their mesophases were characterized by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and switching current response experiments. In all four series one of the terminal tails is varied from OC8H17 to OC16H33. The other terminal tails are OC11H23, O(CH2)(9)CH=CH2, OC10H21 and O(CH2)(8)CH=CH2. The short-tailed compounds show monotropic or enantiotropic B-1 phases and the long-tailed compounds the B-2 phase. The introduction of one terminal vinyl group slightly lowers the transition temperatures. The introduction of a second terminal vinyl group further suppresses the liquid crystalline properties. All compounds with B-2 phases have layer spacings that suggest a tilt of similar to 45 degrees of the bent molecules in the layers, and their switching behaviour is antiferroelectric. 收起