  We present the newly synthesized chiral dopant
2-[(2-isopropyl-5-methylcyclohexyl)oxy]-2-oxoethyl
4-{(E)-[4-(decyloxy)phenyl]diazenyl}benzoate (ChD-3501), consisting of azo- and
aliphatic fragments together with a chiral center based on l-menthol as a
reversible light-controllable chiral dopant. To assess the effects of UV/VIS
irradiation and temperature in the isotropic and liquid crystalline (LC)
states, we studied the spectral kinetics of ethanol solution of ChD-3501, as
well as induction of the cholesteric helix when it was dissolved in nematic LC
(E7) as a chiral dopant. The concentration dependence of the helical pitch of
the induced cholesterics was studied by means on Grandjean-Cano method, and the
helical twisting power of ChD-3501 in the nematic host E7 was determined. The
reversible trans-cis isomerization of chiral dopandt ChD-3501 in E7 under
UV/VIS irradiation was studied, and it has been found that the storage of the
cis-isomer at certain constant temperature also leads to the reversible
isomerisation, which presents a certain interest for applications.
