No abstract

Six banana-shaped compounds with a central core based on a 4,6-dichloro-1,3-phenylene group were synthesized by varying the terminal chains (R5OC 10 H 21 or OC 11 H 21 ) and the lateral substituents (X5H, F or Cl). Their mesophases were characterized by a combination of differential scanning calorimetry, polarizing optical microscopy, triangular wave method, and X-ray diffractometry. Mesomorphic properties of the banana-shaped mesogens with an olefinic group (R5OC 11 H 21 ) as a terminal chain are sensitive to lateral halogen substituents as much as those of the analogues with a saturated group (R5OC 10 H 21 ). The compounds with X5F showed an antiferroelectric switchable smectic phase, which has been designated a B 2 phase. The compounds without a lateral halogen substituent only formed a nematic phase, while the compounds with X5Cl did not exhibit a mesophase in the melt.

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(alkenyloxy) phenyliminomethyl}benzoate]s were synthesized by varying the length of alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C (Sm C *) phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiff's base mesogen induced a decrease in melting temperature and formation of the switchable Sm C * phase in the melt. The smectic phases having the octenyloxy group such as (CH 2) 6 CH=CH 2 showed ferroelctric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm 2 (X=H) and 225 nC/ cm 2 (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.

For Abstract see ChemInform Abstract in Full Text.

Banana-shaped achiral compounds, the 1,3-phenylene bis[4-(alkenyloxyphenyliminomethyl )-benzoate]s, were synthesized with varying length of the alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C (SmC*) phase, were characterized by diVerential scanning calorimetry, polarizing optical microscopy and the triangular wave method. The presence of vinyl groups at the ends of the linear side-wings in the banana-shaped achiral molecules, containing a SchiV 's base mesogen, induced a decrease in melting temperature and formation of the switchable SmC* phase in the melt. The compound having the octenyloxy group exhibited a spontaneous polarization of 120 nC cmÕ 2 on reversal of an applied electric eld.