Three Distinct Polar Phases, Isotropic, Nematic, and Smectic-A Phases, Formed from a Fluoro-Substituted Dimeric Molecule with Large Dipole Moment

Shigemasa Nakasugi; Sungmin Kang; Tso-Fu Mark Chang; Takaaki Manaka; Hiroki Ishizaki; Masato Sone; Junji Watanabe

doi:10.1021/acs.jpcb.3c02259

Three Distinct Polar Phases, Isotropic, Nematic, and Smectic-A Phases, Formed from a Fluoro-Substituted Dimeric Molecule with Large Dipole Moment

J Phys Chem B. 2023 Jul 27;127(29):6585-6595. doi: 10.1021/acs.jpcb.3c02259. Epub 2023 Jul 13.

Authors

Shigemasa Nakasugi^{1

2}, Sungmin Kang^{1

2}, Tso-Fu Mark Chang², Takaaki Manaka³, Hiroki Ishizaki^{1

2}, Masato Sone², Junji Watanabe²

Affiliations

¹ Advanced Technology Research Department, LG Japan Lab Inc., 1-2-13, Takashima, Nishi-ku, Yokohama, Kanagawa 220-0011, Japan.
² Institute of Innovative Research, Tokyo Institute of Technology, 4259, Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan.
³ Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.

PMID: 37439482
DOI: 10.1021/acs.jpcb.3c02259

Abstract

A dimeric molecule, di-5(3FM-C4T), with fluoro-substituted mesogenic cores composed of three-aromatic rings and linked by a pentamethylene spacer is prepared. Di-5(3FM-C4T) forms the ferroelectric nematic (N_F), ferroelectric smectic-A (SmAP_F), and polar isotropic (Iso_P) phases. The N_F phase is composed of molecules in U-shaped conformation that behave like polar rod-like molecules. The reversal spontaneous polarization (P_s) is approximately 8 μC cm^-2, which is extremely large and reflects the huge dipole moment (11.2 D) of the one-side mesogenic core. On the other hand, the SmAP_F phase is formed by bent-shaped molecules. The N_F-SmAP_F phase transition thus follows the conformational change of molecules. The reversal P_s of the SmAP_F phase is around 4 μC cm^-2, which is half of that in the N_F phase, and this is an expected value from the bent shape of the molecules. It is interesting that the highest temperature Iso_P phase still exhibits the polar structure and possibly retains some polar aggregation of molecules in small domains. The three polar phases exhibit the dielectric mode due to the collective polarization fluctuation at around 100 Hz, giving the high dielectric constant over 8000.