Abstract
New 3,4′-disubstituted azobenzene-based mesogens with an azo group joined directly to the central benzene core have been synthesised and their liquid crystalline properties studied. Both molecular arms are gradually elongated by the insertion of a number of benzoate units between the central core and a terminal dodecyloxy chain. Then the lengths of the molecular arms and the overall shape are varied from a rod-like to a hockey-stick-like and bent-shape. Typical bent-shaped mesophases and electro-optical switching can be observed upon reaching a sufficient length of the molecular arms. We demonstrated how the mesoscale organization strictly depends on the molecular shape.
Highlights
Liquid crystalline (LC) materials combine order and mobility on the molecular level and show unique electro-optic properties due to their birefringence and dielectric anisotropy
We present a synthesis and mesomorphic study of a series of materials with an azo group joined directly to the central benzene, creating a 3,40-dihydroxyazobenzene core. We have chosen this type of molecular core as being rigid enough to avoid conformational changes at the central part
While the central core 1 served for the synthesis of compounds A/m/n, both with identical lengths of the arms (m 1⁄4 n) and non-symmetrical materials (m s n), the central core 2 was utilized for preparation of materials A/0/n
Summary
Liquid crystalline (LC) materials combine order and mobility on the molecular level and show unique electro-optic properties due to their birefringence and dielectric anisotropy. In the rst type of hockey-stick-like molecules the bend is introduced by an alkyl or alkoxy chain attached in the meta position of the terminal ring For such a molecule, tilted smectic phases have been found[22,23] with both possibilities of tilt orientation in adjacent layers: synclinic (SmCS) and anticlinic (SmCA). In the second group of hockey-stick-like mesogens the molecules are formed by a bent-shaped central core with arms containing different numbers of aromatic rings. We present a synthesis and mesomorphic study of a series of materials with an azo group joined directly to the central benzene, creating a 3,40-dihydroxyazobenzene core We have chosen this type of molecular core as being rigid enough to avoid conformational changes at the central part. The types of mesophases and their physical properties were monitored by optical microscopy studies, X-ray diffraction analysis, DSC and electro-optical measurements
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