Shape-Persistent V-Shaped Mesogens-Formation of Nematic Phases with Biaxial OrderJournal of Materials Chemistry (2006)
AbstractA homologous series of shape-persistent V-shaped molecules has been designed to form the biaxial nematic phase. Phenyleneethynylene moieties are attached to a bent fluorenone unit to create an apex angle of about 90°, which is determined from the single crystal structure. Two mesogens, one symmetric and another unsymmetric, have been synthesized by attaching a cyano group to one or both of the peripheral phenyl units, respectively. These groups introduce local dipoles essential for the formation of the nematic phases. The tendency to form a crystalline phase is reduced by laterally substituted hexyloxy chains which allow the nematic phase to be supercooled to a glassy state. Two of the three fluorenone derivatives exhibit a transition from the uniaxial nematic to the biaxial nematic phase. This transition has an undetectably small transition enthalpy, but the X-ray diffraction, polarizing optical microscopy, and conoscopy reveal the presence of the biaxial order in the low temperature nematic phase.
- Bent Core Molecules,
- Homologous Series,
- Liquid Crystals,
Citation InformationMatthias Lehmann, Shin-Woong Kang, Christiane Köhn, Sönke Haseloh, et al.. "Shape-Persistent V-Shaped Mesogens-Formation of Nematic Phases with Biaxial Order" Journal of Materials Chemistry Vol. 16 Iss. 44 (2006)
Available at: http://works.bepress.com/satyendra_kumar/53/