1
|
Ogura Y, Akiyama A, Kohri M, Kishikawa K. Positions of Chiral Alkoxy Groups Responsible for Ferroelectricity in a Columnar Liquid Crystal Phase of Diphenylureas with Six Alkoxy Groups. J Phys Chem B 2024; 128:3775-3783. [PMID: 38569005 DOI: 10.1021/acs.jpcb.4c00642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
The columnar polarization direction of ferroelectric columnar liquid crystals can be switched by applying an external electric field, and the polarization direction can be maintained, even after the electric field is removed. If the polarization direction of each column in ferroelectric columnar liquid crystals can be switched and maintained, then ultrahigh-density memory devices can be generated. Recently, we found that the columnar phase of N,N'-bis(3,4,5-tri(S)-citronellyloxyphenyl)urea (Urea-(S)-cit) shows ferroelectricity, whereas that of N,N'-bis(3,4,5-tridecyloxyphenyl)urea (Urea-10) does not. However, the mechanisms by which the six chiral alkoxy groups in Urea-(S)-cit generate ferroelectricity have not been determined. In this study, we regioselectively synthesized four diphenylurea compounds containing (S)-citronellyloxy and decyloxy groups, i.e., N,N'-bis(3,5-di((S)-citronellyloxy)-4-decyloxyphenyl)urea (1), N,N'-bis(4-((S)-citronellyloxy)-3,5-didecyloxyphenyl)urea (2), N,N'-bis(3-((S)-citronellyloxy)-4,5-didecyloxyphenyl)urea (3), and N,N'-bis(3,4-di((S)-citronellyloxy)-5-decyloxyphenyl)urea (4), and investigated which chiral alkoxy group at which position is strongly responsible for the ferroelectricity. The chiral alkoxy groups at 3- and 5-positions of the phenyl groups were clarified to play a significant role in the generation of ferroelectricity. Furthermore, a comparison of these four compounds based on circular dichroism spectroscopy and second harmonic generation experiments revealed the relationship between the helical structure order and the stability of the polarized structure.
Collapse
Affiliation(s)
- Yoshiki Ogura
- Division of Advanced Science and Engineering, Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Azumi Akiyama
- Division of Advanced Science and Engineering, Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Michinari Kohri
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
- Molecular Chirality Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Keiki Kishikawa
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
- Molecular Chirality Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| |
Collapse
|
2
|
Moriya M, Kohri M, Kishikawa K. Chiral Self-Sorting and the Realization of Ferroelectricity in the Columnar Liquid Crystal Phase of an Optically Inactive N, N'-Diphenylurea Derivative Possessing Six (±)-Citronellyl Groups. ACS OMEGA 2021; 6:18451-18457. [PMID: 34308076 PMCID: PMC8296585 DOI: 10.1021/acsomega.1c02534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 06/25/2021] [Indexed: 06/13/2023]
Abstract
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, X-ray 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.
Collapse
Affiliation(s)
- Miyu Moriya
- Department
of Applied Chemistry and Biotechnology, Graduate School of Science
and Engineering, Chiba University, 1-33 Yayoi-cho,
Inage-ku, Chiba 263-8522, Japan
| | - Michinari Kohri
- Department
of Applied Chemistry and Biotechnology, Graduate School of Engineering
and Molecular Chirality Research Center, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Keiki Kishikawa
- Department
of Applied Chemistry and Biotechnology, Graduate School of Engineering
and Molecular Chirality Research Center, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| |
Collapse
|