Uber die drei discotischen Mesophasen der scyllo-Inosithexaester / On the Three Discotic Mesophases of scyllo-Inositol Hexaesters

The mesophases of eleven homologous hexaesters ( 1b -1) of the naturally occurring scylloinositol (1a ) representing the first series of alicyclic saturated discogens are studied by calorimetry and optical microscopy. The three derivatives 1 b -d of this hexahydroxy cyclohexane with each six acetyl, propionyl or butyroyl side chains, respectively, exhibit a very organized discophase D 1 . The hexa-0-acetyl-scyllo-inositol (1b , range of mesophase: Δt = 4.8 °C!) is the discogen having the shortest identical ester groups as lateral functions so far reported for discotic liquid crystals. The pentanoyloxy com pound (1e) exhibits a monotopic D 0 mesophase and an enantiotropic optically isotropic and, probably, cubic mesophase D 0 different from the smectic D mesophase. Versus increasing temperature the phase sequences are D 1 → D E and D 1 → D 0 . Examples of mutual orientation of D 1 and D E discophases and binary mixtures exhibiting stable D E discophase at room temperature are also reported. The mesophases of seven more compounds (1f-1) of the homologous series having lateral functions larger than pentanoyloxy are identified by total miscibility as discophase D E . Their stable temperature ranges are very wide e.g. hexa-0-heptanoyl-scyllo- inositol (1g , Δt = 132 °C) which are exceeded only by those discogens having much larger “cores” (up to now of aromatic character only).