Two ferroelectric phases in a bent-core liquid crystal

We report electro-optical, polarization current, dielectric and SAXS studies on novel bent-core materials that contain four ester groups; three in one arm and only one in the other. These materials differ from each other only by the number of carbons (n) in the alkyloxy chain terminating the one ester containing arm: in Ar 35 n=14, while in Ar 39 n=18. The phase sequences of Ar 35 and 39 are very similar to each other. Both have two mesophases, M1 and M2, with M1 in the 115$^{\circ}$C-140$^{\circ}$C temperature range, and M2 in between about 100$^{\circ}$C and 115$^{\circ}$C. Polarization current measurements indicate polarization current and optical switching in the M$_{1}$ phase with spontaneous polarization and switching time in the Ps$\sim $2.5-3mC/m$^{2}$ and $\tau \quad \sim $200$\mu $s range, respectively. While in Ar 35 the M2 phase cannot be switched, in the AR 39 we could detect polarization switching with a polarization value of about 5-6 mC/m$^{2}$ and switching time over a millisecond. Dielectric and X-ray scattering studies were employed to reveal the fine structure of the M$_{1}$ and M$_{2}$ phases.