Ferro- and antiferroelectric liquid crystals

If a smectic liquid crystal with tilted molecules (smectic-C-type phase) is made chiral, the reduced symmetry leads to the appearance of a spontaneous polarization directed perpendicular to the plane spanned by the smectic layer normal and tilt direction. This makes them naturally antiferroelectric liquid crystals (the chirality also leads to a helical modulation of the tilt direction, and thus of the polarization, hence it is macroscopically cancelled out in this helical antiferroelectric configuration) but by enclosing them between closely spaced substrates that impose planar alignment, they can be turned ferroelectric. This means that the spontaneous polarization is in the same direction over macroscopic areas, directed either up or down with respect to the sample plane, and the direction can be switched by application of an electric field stronger than the coercive threshold. Ferroelectric and antiferroelectric liquid crystals (FLCs and AFLCs, respectively) have characteristic responses to applied electric fields, with two and three distinct states, as illustrated in the figure to the right. In case of FLCs both switched states are stable in the absence of field, whereas AFLCs are monostable.

Prof. Lagerwall has a long tradition of studying ferro- and antiferroelectric liquid crystals, some key publications being the following:

• Current topics in smectic liquid crystal research (Review article)
  Jan P. F. Lagerwall, Frank Giesselmann
  ChemPhysChem, 7, 1, pp. 20-45 (2006)
• Demonstration of the antiferroelectric aspect of the helical superstructures in
  Sm-C*, Sm-Cα* and Sm-Ca* liquid crystals
  Jan P. F. Lagerwall
  Phys. Rev. E, 71, pp. 051703 (2005)
• A chameleon chiral polar liquid crystal: rod-shaped when nematic, bent-shaped when smectic
  Jan P. F. Lagerwall, Frank Giesselmann, Michael D. Wand and David M. Walba
  Chem. Mater. 16, 19, pp. 3606 - 3615 (2004)
• Frustration between syn- and anticlinicity in mixtures of chiral and non-chiral tilted smectic-C-type liquid crystals
  Jan P. F. Lagerwall, Gerd Heppke, Frank Giesselmann
  Eur. Phys. J. E 18, 1, pp. 113-121 (2005)

• On the change in helix handedness at transitions between the Sm-C* and Sm-Ca* phases in chiral smectic liquid crystals
  Jan P. F. Lagerwall, Frank Giesselmann, Mikhail A. Osipov
  Liq. Cryst. 33, 6. pp. 625-633 (2006)
• Ferroelectric polysiloxane liquid crystals with ’de Vries’-type smectic A* -smectic C* transitions
  Martin Rößle, Rudolf Zentel, Jan Lagerwall and Frank Giesselmann
  Liq. Cryst. (Preliminary Communication) 31, 6, pp. 883 - 887 (2004)

At present we are primarily interested in the incorporation of chiral smectics - ferro- or antiferroelectric - in liquid-suspended shells or as the core in coaxial electrospun fibers.
Back to research overview map.