An axially polar-ferroelectric columnar liquid crystal (AP-FCLC) phase that exhibits both switching and maintenance of the macro-polarity in the column axis direction has been achieved in an N,N′-bis(3,4,5-trialkoxyphenyl)urea compound (rac-1) prepared from (±)-citronellyl bromide. Although it had been thought that chirality is necessary to achieve the AP-FCLC phase from our previous study, the optically inactive compound which is a mixture of 21 stereoisomers, generated an AP-FCLC phase. We confirmed its ferroelectricity and investigated the mechanism for realizing the AP-FCLC phase using optoelectronic experiments, Xray diffraction, and circular dichroism spectroscopy. As a result, it was suggested that chiral self-sorting occurs in the columnar liquid crystal phase, in which molecules with a similar stereochemistry form a one-handed helical column, and columns with the same helicity gather together to form a chiral domain. Accordingly, we conclude that the optically inactive compound rac-1 also indicates ferroelectricity similar to that of an optically pure urea compound because of chiral self-sorting.
Melanin
influences light reflection and absorption and is known
to be one of the elements producing structural color, such as that
in the feathers of birds. In this study, we used polydopamine (PDA),
an artificial melanin, as a light-absorbing material and examined
in detail the effect of its composite method on the structural color.
The following two composite methods were investigated using cerium(IV)
oxide (CeO2) particles as a core particle: binary coassembly
of CeO2 and PDA particles and unary assembly of CeO2@PDA core–shell particles. Although both methods dramatically
improved the visibility of the structural color by suppressing the
scattered light owing to the light absorption capability of the PDA,
there was a difference in the particle arrangement, angle dependence
of the structural color, and color tone change. By selecting the PDA
composite method, the guidelines for providing high visibility and
the desired structural color were presented.
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