First ferrocene-containing low molar mass organosiloxane liquid-crystalline materials

Two ferrocene-containing low molar mass organosiloxane liquid-crystalline materials have been synthesised and their phase-transition behaviour investigated. The ω-unsaturated ferrocene precursor was hydrosilylated by addition of pentamethyldisiloxane or heptamethyltrisiloxane in the presence of platinum divinyltetramethyldisiloxane complex. The ferrocene precursor presents smectic A and smectic C phases; the disiloxane compound exhibits a smectic C phase; the trisiloxane compound shows a smectic C phase and two higher order smectic phases. Tilt angle measurements were performed on samples oriented on polytetrafluoroethylene (PTFE) friction deposited layers since rubbed polyimide (PI) only gave very poor alignment. For the precursor the tilt angle was found to be very small, close to 2°, while for the two organosiloxane ferrocene compounds it was close to 28° and almost independent of temperature. These compounds exhibited ferroelectric electro-optic switching properties when doped with 1-2% w/w of chiral mesogens.