LIQUID-CRYSTALLINE 3-ARMED, AND 4-ARMED AND 6-ARMED STAR MOLECULES BASED ON NITROMETHANE-TRISPROPANOL OR PENTAERYTHRITOL WITHOUT MESOGEN SPACERS

Some molecules of unusual shape and apparently non-linear geometry, wi th mesogens tied directly to a central unit (for example, tetrahedral pentaerythritol), have been investigated for liquid crystalline behavi our. It was found that these three-, four- and six-armed 'star' molecu les generated liquid crystalline mesophases, which were characterized by DSC, optical microscopy and X-ray diffraction. The temperature rang es of the fluid mesophases for the thermotropic compounds were above 1 58-degrees-C for the three-armed molecules and above 219-degrees-C for the four-and six-armed 'stars'. All the liquid crystalline compounds exhibited a smectic phase, which appears to be smectic A, with the mol ecules in their fully extended conformations within the layers. Some o f the compounds also had a smectic phase of higher order or a nematic phase.