Dielectric study and helical pitch measurements on a new antiferroelectric liquid crystal

The dielectric dispersion in the ferroelectric and antiferroelectric phases of a new liquid crystal (S)-4-(1-methylheptyloxycarbonyl)-phenyl 4-(4-dodecyloxybenzoyloxy)benzoate has been investigated in the frequency range from 10 Hz to 10 MHz. The behaviour of the soft mode in SmA and the Goldstone mode in SmC* have been determined.;Two dielectric relaxations have been recognized in the antiferroelectric SmCA* phase : the first one between 5 kHz and 50 kHz and the second one, also observable in the ferrielectric SmCFI* phase, around 1 MHz. In SmCFI*, a drastic change in the behaviour of the low frequency response has been found depending on whether the sample was heated or cooled. A sign reversal of the helical pitch has been determined inside the SmCFI* phase, leading to low pitch values of opposite sign in SmCA* and SmC*.