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Article
Shape-Persistent V-Shaped Mesogens-Formation of Nematic Phases with Biaxial Order
Journal of Materials Chemistry (2006)
  • Matthias Lehmann
  • Shin-Woong Kang, Kent State University - Kent Campus
  • Christiane Köhn
  • Sönke Haseloh
  • Ute Kolb
  • Dieter Schollmeyer
  • QingBing Wang, Kent State University - Kent Campus
  • Satyendra Kumar, Kent State University
Abstract
A 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.
Keywords
  • Bent Core Molecules,
  • Homologous Series,
  • Liquid Crystals,
  • Aggregation,
  • Transitions,
  • Particles,
  • Mixtures,
  • Systems
Disciplines
Publication Date
2006
Publisher Statement
Available on publisher's site at http://dx.doi.org/10.1039/b605718g.
Citation Information
Matthias 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/