Influence of the alkyl spacer length on the phase transition behaviour of the Λ-shaped liquid crystal

Article abstract of DOI:10.1080/15421400590956225

We reported that a novel λ-shaped liquid-crystalline molecule 1-6 in which a cyanobiphenyl and two phenylpyrimidine groups are connected to 3, 4-dihydroxy-benzoic acid exhibits an incommensurate SmA phase. In the present study, we have prepared the homolo

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Influence of the Alkyl Spacer
Length on the Phase Transition
Behaviour of the λ-Shaped
Liquid Crystal
Akihisa Yamaguchi a , Atsushi Yoshizawa a , Isa
Nishiyama b , Jun Yamamoto b & Hiroshi Yokoyama b
a Department of Material Science and Technology ,
Faculty of Science and Technology, Hirosaki
University , Hirosaki, Japan
b Yokoyama Nano-structured Liquid Crystal Project,
ERATO, JST , Tokodai, Tsukuba, Japan
Published online: 31 Aug 2006.
To cite this article: Akihisa Yamaguchi , Atsushi Yoshizawa , Isa Nishiyama , Jun
Yamamoto & Hiroshi Yokoyama (2005) Influence of the Alkyl Spacer Length on the
Phase Transition Behaviour of the λ-Shaped Liquid Crystal, Molecular Crystals and
Liquid Crystals, 439:1, 85/[1951]-95/[1961], DOI: 10.1080/15421400590956225
To link to this article: http://dx.doi.org/10.1080/15421400590956225
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Mol. Cryst. Liq. Cryst., Vol. 439, pp. 85=[1951]–95=[1961], 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590956225
Influence of the Alkyl Spacer Length on the Phase
Transition Behaviour of the k-Shaped Liquid Crystal
Akihisa Yamaguchi
Atsushi Yoshizawa
Department of Material Science and Technology, Faculty of Science
and Technology, Hirosaki University, Hirosaki, Japan
Isa Nishiyama
Jun Yamamoto
Hiroshi Yokoyama
Yokoyama Nano-structured Liquid Crystal Project, ERATO, JST,
Tokodai, Tsukuba, Japan
We reported that a novel k-shaped liquid-crystalline molecule I-6 in which a
cyanobiphenyl and two phenylpyrimidine groups are connected to 3, 4-dihydroxy-
benzoic acid exhibits an incommensurate SmA phase. In the present study, we
have prepared the homologous series of the k-shaped molecules I-n (n ¼ 4, 5, 7,
8, 9, 12) and investigated effect of the spacer length on the phase transition behav-
iour. Compounds I-4, I-8 and I-12 with an even member of atoms in spacer showed
the phase sequences of N-SmA-Cr or SmA-Cr. On the other hand, the odd members
I-7 and I-9 showed the phase sequence of N-SmA-SmCanti-Cr.
Keywords: liquid crystal; phase transition; smectic A, smectic Canti
1. INTRODUCTION
The driving force of mesophase formation is a fundamental topic in
the investigation of molecular assembly systems. Recently, molecular
topology [1] and microsegregation [2] have attracted much attention as
We thank Dr. Lianhui Qi of Yokoyama Nano-structured Liquid Crystal Project for
XRD measurements. This work was partly supported by Aomori Prefecture Collabor-
ation of Regional Entities for the Advancement of Technological Excellence, JST.
Address correspondence to Atsushi Yoshizawa, Department of Material Science and
Technology, Faculty of Science and Technology, Hirosaki University, 3, Bunkyo-cho,
Hirosaki 036-8561, Japan. E-mail: ayoshiza@cc.hirosaki-u.ac.jp
85=[1951]

86=[1952]
A. Yamaguchi et al.
FIGURE 1 Molecular structure of the k-shaped liquid-crystalline molecules
I-n.
the origins for producing novel self-organizing systems. In addition,
molecular motion is also important to understand the microscopic
behaviour of liquid-crystalline molecules. Our C-13 NMR study of
smectic liquid crystals revealed that (1) cooperative motion for the core
parts contributes to the orientational order of the molecules in
each layer and (2) inter-layer permeation of tails causes correlation
between cores in adjacent layers [3]. Coupling or competition between
intra-layer core-core interaction and inter-layer interaction can pro-
duce a new class of molecular aggregation. Recently we reported a
novel k-shaped liquid-crystalline molecule, 4-cyanobiphenyl-40-yl 3,
4-bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy} benzoate (I-6),
as shown in Figure 1 [4]. The k-shaped molecule I-6 was found to rea-
lize a stable incommensurate SmA phase. Modification of the k-shaped
structure is expected to produce various organization of molecules.
In the present study, we have prepared the homologous series of the
k-shaped molecules I-n (n ¼ 4, 5, 7, 8, 9, 12) and investigated effect
of the spacer length on the phase transition behaviour.
2. EXPERIMENTAL
Characterization of Materials
The purification of final products was carried out using column chro-
matography over silica gel (63-210 mm) (KANTO CHEMICAL Co.,
INC.) using a toluene-ethyl acetate mixture or a dichloromethane-
ethyl acetate mixture as the eluent, followed by the recrystallization
from an ethanol-chloroform mixture. The purity was checked by
thin layer chromatography (TLC, aluminum sheets, silica gel 60
F254 from Merck). Dichloromethane was used as the solvent. Detec-
tion of products was achieved by UV irradiation (k ¼ 254 and
365 nm).

Mesomorphic Properties of k-Shaped Liquid Crystals
87=[1953]
The structures of the final products were elucidated by infrared (IR)
spectroscopy (BIO RAD FTS-30) and proton nuclear magnetic reson-
ance (1H NMR) spectroscopy (JEOL JNM-GX270). The analyses of
the structures of the products by spectroscopic methods were found
to be consistent with the predicted structures.
Liquid-Crystalline and Physical Properties
The initial phase assignments and corresponding transition tempera-
tures for the final products were determined by optical polarized light
microscopy using
a Nikon Optiphot-pol polarizing microscope
equipped with a Mettler FP82 hot stage and FP80 control processor.
The heating and cooling rates were 5ꢀC minꢁ1. The photomicrographs
were taken using a camera (OLYMPUS DIGITAL CAMERA C-5050
ZOOM) in conjunction with a Nikon Optiphot-pol polarizing micro-
scope. Temperatures and enthalpies of transition were investigated
by differential scanning calorimetry (DSC) using a Seiko Instruments
Inc. DSC6200. The materials were studied at a scanning rate of
5ꢀC minꢁ1 after being encapsulated in aluminum pans. The X-ray scat-
tering experiments were performed using a real-time X-ray diffract-
ometer (Bruker AXS D8 Discover). The monochromatic X-ray beam
¨
(Cu-Ka line) was generated by a 1.6 kW X-ray tube and Gobel mirror
optics. The 2D position sensitive detector has 1024 ꢂ 1024 pixels in a
5 cm ꢂ 5 cm beryllium window. A sample was introduced into a thin
glass capillary tube (diameter 1.0 mm), which was placed in a cus-
tom-made temperature stabilized holder (stability within ꢃ0.1ꢀC).
The X-ray diffraction measurements and the textural observations
by polarized light microscopy using a CCD camera were performed
simultaneously on the sample in the glass capillary tube.
Preparation of Materials
40-Cyanobiphenyl-4-yl 3,4-bis{4-[4-(5-octylpyrimidin-2-yl)
phenoxy]butyloxy} benzoate (I-4)
5-Octyl-2-(4-hydroxyphenyl)pyrimidine (0.57 g, 2.0 mmol) purchased
from Midori Kagaku Co., Ltd. and 1, 4-dibromobutane (0.86 g, 4.0 mmol)
were dissolved in cyclohexanone (10 mL). Potassium carbonate (2.8 g,
2.0 mmol) was then added and the resulting mixture was stirred at
80ꢀC for 6 h. The reaction mixture was filtered and the solvent was
removed by evaporation under reduced pressure. The product was
purified by column chromatography using dichloromethane as the
eluent. 2-[4-(4-Bromobutyloxy)phenyl]-5-octylpyrimidine was obtained.
Yield: 0.62 g (74%).

88=[1954]
A. Yamaguchi et al.
2-[4-(4-Bromobutyloxy)phenyl]-5-octylpyrimidine (0.62 g, 1.5 mmol)
and ethyl 3, 4-dihydroxybenzoate (0.14 g, 0.74 mmol) were dissolved
in cyclohexanone (10 mL). K2CO3 (0.20 g, 1.5 mmol) and KI (0.025 g,
0.15 mmol) were then added and the resulting mixture was stirred
at 145ꢀC for 12 h. The reaction mixture was filtered and the solvent
was removed by evaporation under reduced pressure. The product
was purified by column chromatography using a dichloromethane-
ethyl acetate (20:1) mixture as the eluent, and recrystallized
from an ethanol-chloroform (6:1) mixture (7 mL). Ethyl 3, 4-bis{6-[4-
(5-octylpyrimidin-2-yl)phenyloxy]butyloxy}benzoate was obtained.
Yield: 0.46 g (72%)
Ethyl
3,
4-bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]butyloxy}
benzoate (0.43 g, 0.50 mmol) was added to a solution of KOH
(0.084 g, 1.5 mmol) in ethanol (95%, 10 mL). The resulting mixture
was stirred under reflux for 2 h. The solution was acidified with HCl
(concentrated, 1.0 ml). Water (15 mL) was added to the mixture and
the aqueous phase was extracted with dichloromethane (3 ꢂ 20 mL).
The organic extracts were combined, dried over Na2SO4, filtered and
evaporated. 3, 4-Bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]butyloxy}
benzoic acid was obtained. Yield: 0.38 g (92%).
To a solution of 3, 4-bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]
butyloxy}benzoic acid (0.17 g, 0.20 mmol) in dichloromethane
(10 mL), 4-cyano-40-hydroxybiphenyl (0.040 g, 0.20 mmol), dicyclohex-
ylcarbodiimide (0.042 g, 0.20 mmol) and 4-(N,N-dimethylamino)
pyridine (0.003 g, 0.020 mmol) were added. The resulting solution
was stirred at room temperature overnight. Precipitated materials
were removed by filtration. After removal of the solvent by evapor-
ation, the residue was purified by column chromatography on silica
gel using a toluene-ethyl acetate (15 : 1) mixture. Recrystallization
from ethanol gave the desired product. Yield: 0.14 g (67%).
d
H (270 MHz, CDCl3, TMS): 8.56 (d, 4H, Ar-H, J ¼ 1.4 Hz), 8.34 (dd,
4H, Ar-H, J ¼ 8.9 Hz, 3.0 Hz), 7.83 (dd, 1H, Ar-H, J ¼ 8.5 Hz, 2.2 Hz),
7.74–7.60 (m, 7H, Ar-H), 7.33 (d, 2H, Ar-H, J ¼ 8.9 Hz), 6.99–6.94 (m,
5H, Ar-H), 4.11 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.10 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 4.03 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.02 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 2.58 (t, 4H, ArꢁCH2ꢁ, J ¼ 7.7 Hz), 1.90–1.27 (m, 32H,
aliphatic-H), 0.88 (t, 6H, ꢁCH3, J ¼ 6.6 Hz). n= cmꢁ1(KBr): 2927, 2853
=
=
(CꢁH str.), 2224 (CꢄN str.), 1728 (C O str. ꢁCOOꢁ), 1606, 1584 (C C
str.).
The other compounds presented in this paper were obtained by a
similar method to that for I-4. Analytical data for the other compounds
are given.

Mesomorphic Properties of k-Shaped Liquid Crystals
89=[1955]
40-cyanobiphenyl-4-yl 3,4-Bis{5-[4-(5-octylpyrimidin-2-yl)
phenoxy]pentyloxy} benzoate (I-5)
d
H (270 MHz, CDCl3, TMS): 8.57 (d, 4H, Ar-H, J ¼ 1.4 Hz), 8.37 (dd,
4H, Ar-H, J ¼ 9.2 Hz, 3.0 Hz), 7.83 (dd, 1H, Ar-H, J ¼ 8.5 Hz, 1.9 Hz),
7.74–7.60 (m, 7H, Ar-H), 7.32 (d, 2H, Ar-H, J ¼ 8.4 Hz), 6.98–6.94
(m, 5H, Ar-H), 4.14 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.13 (t, 2H,
ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.05 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.04 (t, 2H,
ꢁOCH2ꢁ, J ¼ 6.5 Hz), 2.59 (t, 4H, Ar-CH2ꢁ, J ¼ 7.7 Hz), 1ꢁ.910–1.27
(m, 44H, aliphatic-H), 0.88 (t, 6H, ꢁCH3, J ¼ 6.6 Hz). n=cm (KBr):
=
2926, 2852 (CꢁH str.), 2223 (CꢄN str.), 1726 (C O str. ꢁCOOꢁ),
=
1606, 1583 (C C str.).
40-Cyanobiphenyl-4-yl 3,4-bis{7-[4-(5-octylpyrimidin-2-yl)
phenoxy]heptyloxy} benzoate (I-7)
dH (270 MHz, CDCl3, TMS): 8.56 (s, 4H, Ar-H), 8.37 (dd, 4H, Ar-H,
J ¼ 9.2 Hz, 2.7 Hz), 7.83 (dd, 1H, Ar-H, J ¼ 8.5 Hz, 1.9 Hz), 7.74–7.60
(m, 7H, Ar-H), 7.32 (d, 2H, Ar-H, J ¼ 8.6 Hz), 6.99–6.93 (m, 5H,
Ar-H), 4.10 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.09 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 4.02 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.01 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 2.59 (t, 4H, ArꢁCH2ꢁ, J ¼ 7.7 Hz), 1.90–1,27 (m, 44H, ali-
phatic-H), 0.88 (t, 6H, ꢁCH3, J ¼ 6.6 Hz). n=cmꢁ1(KBr): 2927, 2853
=
(CꢁH str.), 2228 (CꢄN str.), 1729 (C O str. ꢁCOOꢁ), 1607, 1583
=
(C C str.).
40-Cyanobiphenyl-4-yl 3,4-bis{8-[4-(5-octylpyrimidin-2-yl)
phenoxy]octyloxy} benzoate (I-8)
dH (270 MHz, CDCl3, TMS): 8.59 (s, 4H, Ar-H), 8.37 (d, 4H, Ar-H,
J ¼ 8.4 Hz), 7.83 (dd, 1H, Ar-H, J ¼ 8.5 Hz, 2.2 Hz), 7.74–7.60 (m,
7H, Ar-H), 7.32 (d, 2H, Ar-H, J ¼ 8.6 Hz), 6.99–6.92 (m, 5H, Ar-H),
4.09 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.07 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5
Hz), 4.02 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.01 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 2.60 (t, 4H, ArꢁCH2ꢁ, J ¼ 7.7 Hz), 1.90–1,27 (m, 48H, ali-
ꢁ1
phatic-H), 0.88 (t, 6H, ꢁCH3, J ¼ 6.6 Hz). n=cm (KBr): 2925, 2853
=
(CꢁH str.), 2225 (CꢄN str.), 1728 (C O str. ꢁCOOꢁ), 1606, 1584
=
(C C str.).
40-Cyanobiphenyl-4-yl 3,4-bis{9-[4-(5-octylpyrimidin-2-yl)
phenoxy]nonyloxy} benzoate (I-9)
dH (270 MHz, CDCl3, TMS): 8.56 (s, 4H, Ar-H), 8.37 (dd, 4H, Ar-H,
J ¼ 9.2 Hz, 2.7 Hz), 7.83 (dd, 1H, Ar-H, J ¼ 8.5 Hz, 1.9 Hz), 7.74–7.60
(m, 7H, Ar-H), 7.32 (d, 2H, Ar-H, J ¼ 8.6 Hz), 6.99–6.93 (m, 5H,
Ar-H), 4.10 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.09 (t, 2H, ꢁOCH2ꢁ,

90=[1956]
A. Yamaguchi et al.
J ¼ 6.5 Hz), 4.02 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.01 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 2.59 (t, 4H, ArꢁCH2ꢁ, J ¼ 7.7 Hz), 1.90–1.27 (m, 52H, ali-
phatic-H), 0.88 (t, 6H, ꢁCH3, J ¼ 6.6 Hz). n=cmꢁ1(KBr): 2927, 2853
=
(CꢁH str.), 2228 (CꢄN str.), 1729 (C O str. ꢁCOOꢁ),1607, 1583
=
(C C str.).
40-Cyanobiphenyl-4-yl 3,4-bis{12-[4-(5-octylpyrimidin-2-yl)
phenoxy]dodecyloxy} benzoate (I-12)
dH (270 MHz, CDCl3, TMS): 8.59 (s, 4H, Ar-H), 8.37 (d, 4H, Ar-H,
J ¼ 8.4 Hz), 7.83 (dd, 1H, Ar-H, J ¼ 8.5 Hz, 2.2 Hz), 7.74–7.60
(m, 7H, Ar-H), 7.32 (d, 2H, Ar-H, J ¼ 8.6 Hz), 6.99–6.92 (m, 5H, Ar-
H), 4.09 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.07 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 4.02 (t, 2H, ꢁOCH2ꢁ, J ¼ 6.5 Hz), 4.01 (t, 2H, ꢁOCH2ꢁ,
J ¼ 6.5 Hz), 2.60 (t, 4H, ArꢁCH2ꢁ, J ¼ 7.7 Hz), 1.90–1.27 (m, 64H,
aliphatic-H), 0.88 (t, 6H, ꢁCH3, J ¼ 6.6 Hz). n=cmꢁ1(KBr): 2928, 2855
=
(CꢁH str.), 2223 (CꢄN str.), 1727 (C O str. ꢁCOOꢁ), 1606, 1585
=
(C C str.).
3. RESULTS AND DISCUSSION
Phase Transition Behaviour
Transition temperatures and transition enthalpies for the homologous
series of k-shaped liquid-crystalline molecules I-n, measured by
optical polarized light microscopy and differential scanning calor-
imetry (DSC) are listed in Table 1. A large odd-even effect on the clear-
ing temperatures is apparent in which the even members of the series
exhibit the higher values. The enthalpy changes associated with the
TABLE 1 Transition Temperatures (ꢀC) and Transition Enthalpies (kJ molꢁ1
(in Square Brackets) for I-n
)
n
Phase transition temperatures
4
5
6
Iso 209[15.7] SmA 109[27.1] recryst. mp 133
Iso 148[1.9] N 144[0.95] SmA 100[45.2] recryst. mp 128
Iso 183[7.9] N 177[1.1] SmA 157[0.65] SmAinc 113[39.2] recryst.
mp 150
7
Iso 145[2.4] N 129[4.2] SmA 127[3.0] SmCanti 64[25.2] recryst.
mp 130
8
9
Iso 166[8.7] N 162[8.8] SmA 112[46.6] mp 148
Iso 141[4.4] N 137[7.6] SmA 132[0.95] SmCanti 56[21.7] recryst.
mp 127
12
Iso 150[23.2] SmA 81[34.7] recryst. mp 118

Mesomorphic Properties of k-Shaped Liquid Crystals
91=[1957]
FIGURE 2 A photomicrograph of the SmCanti phase in a pseudo-homeotropi-
cally aligned region for compound I-7.
Iso-N transition for the series also show a pronounced alternation as
the length and parity of the spacer is varied. The values for the Iso-
N enthalpy for the even members are several times larger than those
for the odd members. All of the homologous series studied here showed
the SmA phase. As our previous report, I-6 exhibited an unusual
incommensurate SmA (SmAinc) phase [4]. In this study, the homolo-
gous series except for I-6 did not show the SmAinc phase. It is noted
that some of the odd members, I-7 and I-9, showed the SmCanti phase.
The marked odd-even effect on the phase sequence is apparent. A
photomicrograph of the SmCanti phase in a pseudo-homeotropically
aligned region for I-7 is shown in Figure 2. The Schlieren textures
clearly showed two and four brush singularities of the smectic phase.
The two brush singularities are not allowed to be formed in the
synclinic phase but can be generated with anticlinic ordering [5].
X-ray Diffraction Studies
Figure 3 shows intensity profiles of the wide angle X-ray scattering for
the homologous series of the k-shaped compounds I-n. Diffuse scatter-
ing in the wide angle region was observed for all of the smectic phases

92=[1958]
A. Yamaguchi et al.
FIGURE 3 X-ray scattering patterns of I-n.
of the homologues, indicating that there is no long range positional
order within the layers. The estimated molecular length (l) from
MM2 calculation and the layer spacing (d) obtained from the X-ray
scattering experiments are summarized in Table 2. The obtained layer
˚
spacings of the SmA phase for I-5 and I-6 were about 52 and 55 A

Mesomorphic Properties of k-Shaped Liquid Crystals
93=[1959]
FIGURE 4 Expected molecular configurations and lengths by the MM2
method.
˚
whereas the estimated molecular lengths were about 38 and 43 A
respectively. The longer layer spacings than the molecular lengths
suggest the formation of an interdigitated layer structure for the
SmA phases of I-5 and I-6. On the other hand, the obtained layer
spacings of the SmCanti phase for I-7 and the SmA phase for I-12
TABLE 2 Molecular Lengths (l) and Layer Spacings (d) of I-n.
a
b
˚
˚
d=A
Compound
Mesophase
l=A
I-5
I-6
SmA
SmA
38
43
52
55
SmAinc
SmCanti
SmA
55, 40, 23
22.7
27.2
I-7
I-12
41
50
aEstimated by MM2 calculation.
bCalculated from the X-ray diffraction peak that appeared in the small angle region.

94=[1960]
A. Yamaguchi et al.
˚
were about 23 and 27 A whereas the molecular lengths were estimated
˚
to be about 41 and 50 A respectively. The approximately half layer
spacings compared to the molecular lengths suggest the smectic
phases form an intercalated layer structure [6]. The ability to accom-
modate the terminal chains in the space between the intercalated
layers of mesogenic groups is determined largely by the length of
the spacer. Thus, for the intercalated phases to be observed the
terminal chain must be equal to or shorter in length than the spacer.
If the terminal chain is considerably longer than the spacer, then
interdigitated phases are observed [6]. For compound I-6 in which
the terminal chain is equal to the spacer, thus the intermediate state
appeared. Three periodic density waves were observed in the SmAinc
phase, indicating that interdigitated, intercalated and monolayered
structures coexist [4].
Then we discuss the appearance of the SmCanti phase for the odd
members. Estimated molecular lengths and configurations calculated
by the MM2 method for I-6 and I-7 are also shown in Figure 5. The odd
member I-7 was found to adopt more bent configuration compared to
the even member I-6. The bent configuration seems to be reasonable
for the formation of the intercalated SmCanti phase for I-7. However,
the odd member I-5 with bent configuration showed no SmCanti
phase. This is considered to be due to the difference of the layer struc-
ture between I-5 and I-7, i.e., I-5 has the interdigitated smectic phase
whereas I-7 has the intercalated one.
4. CONCLUSIONS
We have prepared the homologous series of the k-shaped liquid-
crystalline molecules and investigated the phase transition behaviour.
XRD studies indicate that appearance of the SmAinc phase for I-6 in
which the terminal chain is equal to the spacer results from compe-
tition between interdigitated and intercalated layer structures. A
marked odd-even effect on transition behaviour was observed. It is
noted that some of the odd members, I-7 and I-9, showed the SmCanti
phase.
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Mesomorphic Properties of k-Shaped Liquid Crystals
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