Study of unsymmetrical dimesogens containing 4-heptylazobenzene

Authors

  • V. Ajay Mallia,

    1. Molecular Smart System Group, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
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  • Masahiro Funahashi,

    1. Molecular Smart System Group, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
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  • Nobuyuki Tamaoki

    Corresponding author
    1. Molecular Smart System Group, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
    • Molecular Smart System Group, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
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Abstract

4-Heptylazobenzene (HAB) has been covalently attached to cholesterol (Ch) by varying the methylene spacers and to cyanobiphenyl (CB) moiety with an octyl methylene linkage. Enhancement of short-range translational correlations in the chiral nematic (N*) phase has been observed by the introduction of HAB moiety. HAB–Ch dimesogens exhibit chiral smectic C (SmC*), chiral smectic A (SmA*) and N* phases depending on the methylene spacer length. The dimesogen containing HAB–CB shows a SmA and an N phase. The HAB–Ch dimesogen with octyl methylene spacer shows co-existence of multiple periodicities in its SmA* as well as in SmC* phases. A dramatic increase of >150 nm in the N* reflected wavelength shift (Δλ) with change in temperature has been observed for the HAB-Ch dimesogen containing an octyl spacer compared to the similar dimesogen that does not have a heptyl side chain. Ferroelectric switching has been studied for a representative dimesogen containing HAB-Ch having hexyl spacer in its SmC* phase, the spontaneous polarization value was determined to be 150 nC cm−2 (at 125 °C) by applying a triangular wave field. A reversible photochemical switching between SmA and N phases also has been reported for the dimesogen containing HAB–CB. Copyright © 2007 John Wiley & Sons, Ltd.

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