170
Published on the web January 30, 2010
Chiral T-shaped Semiflexible Compound Exhibiting a Wide Temperature Range Blue Phase III
Hirotoshi Iwamochi,1 Tetsu Hirose,2 Yutaro Kogawa,1 and Atsushi Yoshizawa*1
1Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University,
3 Bunkyo-cho, Hirosaki 036-8561
2Tohoku Chemical Corporation, 1-3-1 Kanda, Hirosaki 036-8655
(Received October 27, 2009; CL-090955; E-mail: ayoshiza@cc.hirosaki-u.ac.jp)
We have designed a chiral T-shaped compound possessing a
O
O
O
C H
O
8
17
flexible spacer, which was found to exhibit a blue phase III with
a temperature range of about 30 K including room temperature
on cooling. Furthermore, the BPIII changed to a glass phase.
Electrooptical switching was observed at all temperatures of the
BPIII.
H
O
(CH )
O
2 5
CH
3
O
O
C H
6 13
(CH )
2 5
O
CN
Blue phases are of particular interest because they have a
fluid lattice, the structure of which is stabilized by lattice defects.
They are classifiable as blue phase I (BPI), blue phase II (BPII),
or blue phase III (BPIII) depending on their double-twist-
cylinder packing structure.1,2 The BPI packing structure is a
body-centered cubic structure; that of BPII is a simple cubic
structure.3,4 Theoretical investigations have revealed that BPIII
and the isotropic phase have identical symmetry.5 It is expected
that BPIII consists of double twist cylinders with arbitrary
orientation.1,6,7 Blue phases are normally found in a narrow
(ca. 1 K) temperature range between the isotropic liquid and a
chiral nematic (N*) phase of sufficiently short pitch. Electric
field effects in blue phases have been investigated.1 Blue phases
have potential applications as fast light modulators or tunable
photonic crystals. However, their narrow temperature range
poses a daunting obstacle to their application. Therefore,
stabilizing the blue phases has attracted much attention.8-18
Recently, we reported an electric field induced phase
transition between BPIII and N phases of a chiral T-shaped
liquid crystal.19 Actually, BPIII has a twisted nematic order that
exists microscopically, although it appears to be macroscopi-
cally isotropic. Furthermore, BPIII has no periodic defects.
Therefore, a well black state is obtainable without surface
treatment. Then a homogeneous bright state is achieved in the
electric field induced N phase. However, some problems remain
for application of this technology to display devices: broadening
of the temperature range, reduction of the driving voltage, and
improvement of the response speed. Herein, we report a chiral
T-shaped compound possessing a flexible spacer. The compound
was found to exhibit BPIII with a wide temperature range of
about 30 K including room temperature.
1
Figure 1. Molecular structure of compound 1.
O
H3CO
CH3
C
O
COOH
NC
OH
HO CH C6H13
DEAD / P(C6H5)3 / THF
*
O
K2CO3
/
Br(CH2)5COOC2H5
O
*
H3CO
C
O
COO-CH(CH3)-C6H13
NH3 (aq)
NC
O (CH2)5 COOC2H5
*
HO
COO-CH(CH3)-C6H13
1) NaOH /THF-H2O
2) HCl
DEAD / P(C6H5)3 / THF
HO (CH2)5
OH
*
(CH2)5
O
COO-CH(CH3)-C6H13
HO
NC
O (CH2)5 COOH
C8H17
O
COOH
DCC / DMAP / CH2Cl2
OH
*
C8H17
O
COO (CH2)5
OH
O
COO-CH(CH3)-C6H13
DCC / DMAP / CH2Cl2
1
Molecular structure of the chiral T-shaped compound (S)-1-
methylheptyl 4¤-({4-octyloxy-2-[6-(4-cyanobiphenyl-4¤-yloxy)-
hexanoyloxy]benzoyloxy}pentyloxy)biphenyl-4-carboxylate (1)
is presented in Figure 1. Figure 2 shows the scheme of synthesis
of compound 1. The purity of the final compound was checked
using elementary analysis. The structure was elucidated using
proton nuclear magnetic resonance (1H NMR) spectroscopy.20
The phase transition behavior of compound 1 was inves-
tigated using polarized optical microscopy (BX-51; Olympus
Corp.) equipped with a temperature control unit (LK-600PM;
Japan High Tech Co., Ltd.) and differential scanning calorimetry
Figure 2. Synthetic scheme of compound 1.
(DSC 6200 calorimeter; Seiko Co., Ltd.). On cooling at a rate of
5 °C min¹1, compound 1 showed the following phase sequence:
isotropic liquid 24.7 °C (1.0 kJ mol¹1) BPIII ¹8.2 °C glass
phase; the melting temperature was 75 °C. The blue phase
showed fluidity; it did not appear as platelets that are usually
observed in BPI or BPII, thereby indicating that the blue phase is
BPIII. The Iso-BPIII transition temperature was independent
of the cooling rate. On the cooling at a rate of 0.5 °C min¹1, it
was 25.2 °C. Compound 1 was found to exhibit BPIII with a
Chem. Lett. 2010, 39, 170-171
© 2010 The Chemical Society of Japan
Iwamochi, Hirotoshi
