Two ferrocene-containing low molar mass organosiloxane liquid-crystalline materials have been synthesised and their phase-transition behaviour investigated. The v-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.(structures 2 and 3), which represent a novel family of metalIntroduction based anisotropic materials (see Synthesis and Fig. 1). We will There is a growing interest in metal-containing liquidpresent data for two homologues, containing 2 and 3 silicon crystalline materials1,2 that combine some of the properties of atoms, in comparison with the v-unsaturated ferrocene precurmetals with those of mesogenic moieties since this could lead sor. This will allow us to demonstrate that, despite its relatively to processable materials with interesting anisotropic optical, small size compared to the bulky ferrocene mesogenic group, electronic and magnetic properties. Owing to its unique redox the siloxane moiety plays an important role in the phase characteristics, ferrocene is a valuable unit for building up stability, phase sequence, electro-optic properties and quality switchable systems3 and recently, electron transfer was used of the surface alignment. to generate mesomorphism in the ferrocene-ferrocenium redox system.4Ferrocene-containing side-chain liquid-crystal polymers
Experimental(SCLCPs) have been reported in the literature.1,2,5 The SCLCPs offer several advantages over the low molar mass Synthesis liquid crystals in that they have better mechanical characterThe ferrocene precursor 1 was synthesised as previously istics, a broader mesomorphic range and a reduced or supdescribed.2 1,1,1,3,3-Pentamethyldisiloxane, 1,1,1,3,3,5,5-heppressed tendency to form crystalline phases. However, because tamethyltrisiloxane and the platinum catalyst (platinumof the rigidity of the polymer backbone, the SCLCPs are divinyltetramethyldisiloxane complex, 3-3.5% platinum conusually highly viscous and therefore have long switching centration in vinyl terminated polydimethylsiloxane, neutral ) response times.6 The SCLCPs based on flexible polysiloxane were purchased from Fluorochem. Toluene was freed of thiobackbones have shorter response times than those based on phene according to standard procedures and then dried over m...
