Published on Web 07/16/2005
Odd-Even Behavior of Ferroelectricity and Antiferroelectricity
in Two Homologous Series of Bent-Core Mesogens
Seng Kue Lee,†,‡ Sung Heo,† Jong Gun Lee,† Kyung-Tae Kang,†
Kazuya Kumazawa,‡ Koushi Nishida,‡ Yoshio Shimbo,‡ Yoichi Takanishi,‡
Junji Watanabe,‡ Takayuki Doi,§ Takashi Takahashi,§ and Hideo Takezoe*,‡
Contribution from the Department of Chemistry and Chemistry Institute for Functional
Materials, Pusan National UniVersity, Pusan 609-735, Korea, Department of Organic and
Polymeric Materials, Tokyo Institute of Technology, O-okayama 2-12-1, Meguro-ku,
Tokyo152-8552, Japan, and Department of Applied Chemistry, Tokyo Institute of Technology,
O-okayama 2-12-1, Meguro-gu, Tokyo152-8552, Japan
Received April 10, 2005; E-mail: htakezoe@o.cc.titech.ac.jp
Abstract: Two chiral bent-core mesogens Pn-O-PIMB(n - 2)* (n ) 9 and 10) and their oxygen analogues
Pn-O-PIMB(n - 2)*-(n - 4)O (n ) 8, 9, and 10) with ω-[(S)-amyloxy]alkoxy terminal groups were
prepared, and their phase structures were investigated by means of electro-optic, polarization reversal
current and second harmonic generation measurements in order to clarify the effect of the interlayer steric
interaction on the emergence of polar orderings. The odd-even behavior for the alternative appearance of
ferroelectricity and antiferroelectricity was observed in two homologous series; the bent-core mesogens
P10-O-PIMB8*, P8-O-PIMB6*-4O, and P10-O-PIMB8*-6O in addition to the previously reported
P6-O-PIMB4* and P8-O-PIMB6*, where the length of chains n is even, exhibited ferroelectric phases.
On the contrary, the mesogens P7-O-PIMB5*, P9-O-PIMB7*, and P9-O-PIMB7*-5O, where n is
odd, showed antiferroelectric phases. It is obvious that the interlayer steric interaction plays a major role
for the emergence of a variety of phase structures.
1. Introduction
and only a few ferroelecric bent-core mesogens have been
reported.7-14 This is quite natural from the viewpoint of
interlayer steric interaction. Namely, SmCSPA is the only
structure that satisfies the condition that the terminal chains in
adjacent layers are parallel to each other. An intentional attempt
to suppress SmCSPA and to obtain the ferroelectric phase was
made by Walba et al.15 by introducing the same chiral terminal
chain as that of a material (MHPOBC) showing the smectic
CA* (SmCA*), anticlinic organization of rodlike molecules.
Since Niori et al.1 discovered that achiral bent-core (banana-
shaped) molecules possess unusual and interesting properties,
i.e., unique polarity and supramolecular chirality, much attention
has been paid for these materials. The investigation of the
relationship between the molecular structure and mesomorphic
properties is very important to liquid crystal chemistry. That
is, a series of liquid crystals with a systematic structural variation
have to be synthesized to examine the relationship between the
chemical structures and their physical properties, particularly
the polar orders in the bent-core mesogens. For that purpose,
new synthetic methods have to be developed.
Among seven phases, B1-B7, the most widely studied is
the B2 phase, in which four structures are known to exist
depending on tilt and polar correlations between adjacent layers;
SmCS,APF,A. Here the first two subscripts, S and A, specify
syn- and anticlinicity, and the second two subscripts, F and A,
specify ferro- and antiferroelectricity, respectively. As in
Pn-O-PIMB with achiral terminal alkoxy chains, most of bent-
core mesogens exhibit the antiferroelectric mesophase,2-6
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† Pusan National University.
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‡ Department of Organic and Polymeric Materials, Tokyo Institute of
Technology.
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Achard, M. F. Liq. Cryst. 2001, 28, 1285-1292.
§ Department of Applied Chemistry, Tokyo Institute of Technology.
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G.; Weissflog, W. Angew. Chem., Int. Ed. 2005, 44, 774-778.
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M, A.; Clark, N. A. Science 2000, 288, 2181-2184.
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10.1021/ja052315q CCC: $30.25 © 2005 American Chemical Society
J. AM. CHEM. SOC. 2005, 127, 11085-11091
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