Synthesis, structure, and mesomorphism of novel liquid crystalline acrylate monomers and polymers

Article abstract of DOI:10.1080/15421406.2015.1017295

A series of novel liquid crystalline monomers (M₁-M₈) and side chain polymers base polyacrylate backbone were synthesized. The chemical structures were characterized by FT-IR and ¹H-NMR spectra. The mesomorphism and thermal behavior was investigated by polarizing optical microscopy, differential scanning calorimetry, and thermogravimetric analysis. The relationships of structure and mesomorphism are discussed in detail. The eight monomers and their corresponding polymers all show enantiotropic nematic phase. With increasing the spacer length or flexibility of the terminal group, the melting temperature (T_m) and isotropic temperature (T_i) of the corresponding monomers and polymers all decreased. However, with increasing the rigidity of the mesogenic core, T_m and T_i of the corresponding monomers and polymers all increased. TGA showed that all the polymers obtained in this study had excellent thermal stability.

Full text of DOI:10.1080/15421406.2015.1017295

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Synthesis, structure, and mesomorphism of novel
liquid crystalline acrylate monomers and polymers
Xiao-Xu Xu, Chun-Ying Chao & Xi-Jing Yao
To cite this article: Xiao-Xu Xu, Chun-Ying Chao & Xi-Jing Yao (2016) Synthesis, structure,
and mesomorphism of novel liquid crystalline acrylate monomers and polymers, Molecular
Crystals and Liquid Crystals, 624:1, 1-10
To link to this article: http://dx.doi.org/10.1080/15421406.2015.1017295
Published online: 11 Feb 2016.
Submit your article to this journal
Article views: 10
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gmcl20
Download by: [University of California, San Diego]
Date: 18 February 2016, At: 07:41

MOL. CRYST. LIQ. CRYST.
, VOL. , NO. , –
http://dx.doi.org/./..
Synthesis, structure, and mesomorphism of novel liquid
crystalline acrylate monomers and polymers
Xiao-Xu Xua, Chun-Ying Chaob, and Xi-Jing Yaob
aCollege of Chemical Engineering and Material, Eastern Liaoning University, Dandong, P. R. China; bCenter for
Molecular Science and Engineering, College of Science, Northeastern University, Shenyang, P. R. China
ABSTRACT
KEYWORDS
Acrylate monomer; liquid
crystalline polymer; nematic
phase; synthesis
A series of novel liquid crystalline monomers (M1−M8) and side chain
polymers base polyacrylate backbone were synthesized. The chemical
structures were characterized by FT-IR and 1H-NMR spectra. The meso-
morphism and thermal behavior was investigated by polarizing opti-
cal microscopy, differential scanning calorimetry, and thermogravimet-
ric analysis. The relationships of structure and mesomorphism are dis-
cussed in detail. The eight monomers and their corresponding polymers
all show enantiotropic nematic phase. With increasing the spacer length
or flexibility of the terminal group, the melting temperature (Tm) and
isotropic temperature (Ti) of the corresponding monomers and poly-
mers all decreased. However, with increasing the rigidity of the meso-
genic core, Tm and Ti of the corresponding monomers and polymers all
increased. TGA showed that all the polymers obtained in this study had
excellent thermal stability.
1. Introduction
The area of liquid crystals (LCs) arguably is one of the most extensive and dynamic fields
of present-day materials research [1, 2]. LC materials combine order and mobility and form
well-organized supramolecular assemblies that exhibit a variety of physical properties [3–6].
Therefore, as new functional materials, they can provide interesting studies of molecular
aggregation in which the driving forces of self assembly can be studied in a systematic and
controlled manner [7].
For side chain liquid crystalline polymers (LCPs), their mesomorphism depends on the
nature of polymer backbone, the type of mesogen, the flexible spacer length, and the nature of
terminal groups [8–15]. The mesogens are usually attached to the polymer backbone through
the flexible spacer. The polymer backbone and mesogens have antagonistic tendencies: the
polymer backbone is driven toward a random coil-type configuration, whereas the meso-
gens stabilize with long-range orientational order. The flexible spacer, which is usually an
aliphatic hydrocarbon chain containing, normally, more than two methylene units, decouples
the mesogenic side groups from the polymer backbone and renders the mesogens to orien-
tational order. Recently, many new LC materials have been reported [16–22]. Therefore, it is
CONTACT Xiao-Xu Xu
dong, , P. R. China.
x.@.com
College of Chemical Engineering and Material, Eastern Liaoning University, Dan-
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
©  Taylor & Francis Group, LLC

2
X.-X. XU ET AL.
both necessary and useful to synthesize various kinds of LC material to study the relationship
of the structure and properties, and explore their potential applications.
In this paper, eight new LC monomers and polymers were prepared and characterized. The
mesomorphism and thermal behavior were investigated with polarizing optical microscopy
(POM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The
structure–property relationships of the monomers and polymers obtained in this study are
discussed.
2. Experimental
2.1. Materials
2-Chloroethanol was purchased from Tianjin Dagu Chemical Plant. 6-Chlorohexanol from
Zhouping Mingxing Chemical Engineering Co., Ltd. 4-Hydroxybenzoic acid was obtained
from Shanghai Wulian Chemical Plant. Acrylic acid was purchased from Shenyang Hefu
Chemical Reagent Co., Ltd. 4-Ethylbenzoic acid and p-benzenediol was purchased from Bei-
jing Chemical Plant. 4-Pentylbenzoic acid was purchased from Yantai Xianhua Chemical
Engineering Co., Ltd. 4,4ꢀ-Dihydroxybiphenyl (from Aldrich) was used as received. All sol-
vents and reagents used were purified by standard methods.
2.2. Measurements
FT-IR spectra were measured on a Perkin-Elmer spectrum One (B) spectrometer. 1H-NMR
spectra were obtained with a Bruker ARX400 spectrometer. The average molecular weight
of the polymer was obtained with Waters gel permeation chromatography (GPC) 1515. A
Leica DMRX POM equipped with a Linkam THMSE-600 heating and cooling stage was used
to observe the phase transition temperatures and analyze the mesomorphism through the
observation of optical textures. The phase behavior was determined with a Netzsch DSC
204 equipped with a cooling system. The heating and cooling rates were 10°C/min. Thermal
decomposition temperature data were measured under nitrogen atmosphere with a Netzsch
TGA 209C thermogravimetric analyzer at a heating rate of 20°C/min.
2.3. Synthesis of the compounds
The synthetic route of the compounds 1–8 is outlined in Scheme 1. 4-(2-
Hydroxyethoxy)benzoic acid (1), 4-(6-hydroxyhexyloxy)benzoic acid (2),
4-(2-(acryloyloxy)ethoxy)benzoic acid (3), and 4-(6-(acryloyloxy)hexyloxy) benzoic acid
(4) were prepared according to the method reported previously [23–25].
... -Hydroxyphenyl-ꢀ-ethylbenzoate ()
4-Ethylbenzoyl chloride (16.8 g, 0.1 mol) was dissolved in 20 mL of dry tetrahydrofuran
(THF), and then added dropwise to the stirred solution of p-benzenediol (55 g, 0.5 mol) in
200 mL of THF and 8mL of pyridine. The mixture was reacted for 4 hr at room temperature,
and refluxed for 6 hr. After the reaction solution was concentrated, the residue was poured
into beaker filled with 500 mL of ice-water, the crude product was washed with warm water,
and recrystallized from ethanol. Yield: 67 %. mp: 132°C. FT-IR (KBr, cm−1): 3447 (–OH);
=
2971, 2880 (CH3–, –CH2–); 1713 (C O); 1605, 1575 (Ar–).

MOL. CRYST. LIQ. CRYST.
3
Scheme . Synthesis of the compounds 1–8 and monomers M1−M8.
... -Hydroxyphenyl-ꢀ-pentylbenzoate ()
The compound 6 was prepared by a procedure similar to that for 5. Recrystallized from
ethanol. Yield: 63%. mp: 110°C. FT-IR (KBr, cm−1): 3387 (–OH); 2952, 2826 (CH3–, –CH2–);
=
1721 (C O); 1600, 1510 (Ar–).
... -Hydroxybiphenyl-’-ethylbenzoate ()
4-Pentylbenzoyl chloride (8.4 g, 0.04 mol) was dissolved in 10 mL of dry tetrahydrofuran
(THF), and then added dropwise to the stirred solution of 4,4ꢀ-dihydroxybiphenyl (29.8 g,
0.16 mol) in 120 mL of THF and 4mL of pyridine. After the mixture was refluxed for 10h, the
reaction solution was poured into beaker filled with 1000 mL of ice-water, the crude product,
obtained by filtration, was washed with 1.5% NaOH solution and ethanol, and recrystallized
from ethanol/acetone (1:1). Yield: 33%. mp: 211°C. FT-IR (KBr, cm−1): 3390 (–OH); 2962,
=
2876 (CH3–, –CH2–); 1726 (C O); 1606, 1583 (Ar–).
... -Hydroxybiphenyl-’-pentylbenzoate ()
The compound 8 was prepared by a procedure similar to that for 7. Recrystallized from
ethanol/acetone (2:1). Yield: 339%. mp: 173°C. FT-IR (KBr, cm−1): 3420 (–OH); 2960, 2818
=
(CH3–, –CH2–); 1738 (C O); 1613, 1594 (Ar–).
2.4. Synthesis of the monomers
The synthetic route of the acrylate monomers M1–M8 is shown in Scheme 1. The synthesis of
M1–M8 is presented by the same method.

4
X.-X. XU ET AL.
... -(-(-(Acryloyloxy)ethoxy)benzoyloxy)phenyl-ꢀ-ethylbenzoate (M)
The compounds 3 (2.36 g, 0.01 mol) and 5 (2.42 g, 0.01 mol) were dissolved in 45 ml of CH2Cl2
at 30°C. N,Nꢀ-Dicyclohexylcarbodiimide (DCC) (1.03 g, 0.01 mol) and a small amount of 4-
dimethylaminopyridine (DMAP) were dissolved in 5 ml of CH2Cl2, and then added drop-
wise to the above solution. The reaction mixture was stirred for 24 hr at 30°C. After a small
amount of water was added into the resulting solution, and filtered. The filtrate was dried
with anhydrous MgSO4, and evaporated to dryness. The crude product obtained was purified
by silica gel column chromatography (ethyl acetate/hexane = 1/2). White solid was obtained.
−1
=
=
Yield: 72%. FT-IR (KBr, cm ): 3028 ( C—H); 2967, 2872 (–CH2–); 1731, 1714 (C O); 1636
1
=
(C C); 1605, 1575 (Ar–); 1277 (C—O—C). H-NMR (CDCl3, TMS, δ, ppm): 1.23–1.28 (t,
3H, –CH3); 2.70–2.75 (m, 2H, –CH2CH3); 4.25–4.54 [m, 4H, –COO(CH2)2O–)]; 5.84–5.87
and 6.41–6.46 (m, 2H, CH2 =); 6.12–6.19 (m, 1H, CH2 = CH–); 6.97–8.16 (m, 12H, Ar—H).
... -(-(-(Acryloyloxy)hexyloxy)benzoyloxy)phenyl-ꢀ-ethylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/2). White solid was
−1
=
obtained. Yield: 62%. FT-IR (KBr, cm ): 3075 ( C–H); 2958, 2854 (–CH2–); 1744, 1727
1
=
=
– –
(C O); 1636 (C C); 1601, 1579 (Ar–); 1268 (C O C). H-NMR (CDCl3, TMS, δ, ppm):
1.24–1.28 (t, 3H, –CH3); 1.45–1.82 [m, 8H, –COOCH2(CH2)4CH2O–)]; 2.71–2.76 (m, 2H, –
CH2CH3); 3.99 [t, 2H, –COOCH2(CH2)4CH2O–)]; 4.12 [t, 2H, –COOCH2(CH2)4CH2O–)];
5.85–5.87 and 6.41–6.47 (m, 2H, CH2 =); 6.11–6.17 (m, 1H, CH2 = CH–); 7.01–8.18 (m,
12H, Ar–H).
... -(-(-(Acryloyloxy)ethoxy)benzoyloxy)biphenyl-ꢀ-ethylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/1). White solid was
−1
=
obtained. Yield: 52%. FT-IR (KBr, cm ): 3036 ( C–H); 2961, 2872 (–CH2–); 1739, 1714
1
=
=
– –
(C O); 1636 (C C); 1601, 1571 (Ar–); 1278 (C O C). H-NMR (CDCl3, TMS, δ, ppm):
1.23–1.29 (t, 3H, –CH3); 2.71–2.75 (m, 2H, –CH2CH3); 4.27–4.55 [m, 4H, –COO(CH2)2O–)];
5.85–5.89 and 6.40–6.46 (m, 2H, CH2 =); 6.14–6.20 (m, 1H, CH2 = CH–); 6.99–8.19 (m, 16H,
Ar–H).
... -(-(-(Acryloyloxy)hexyloxy)benzoyloxy)biphenyl-ꢀ-ethylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/1). White solid was
−1
=
=
obtained. Yield: 61%. FT-IR (KBr, cm ): 3062 ( C–H); 2932, 2859 (–CH2–); 1735 (C O);
1
=
– –
1635 (C C); 1601, 1571 (Ar–); 1272 (C O C). H-NMR (CDCl3, TMS, δ, ppm): 1.25–1.28
(t, 3H, –CH3); 1.46–1.83 [m, 8H, –COOCH2(CH2)4CH2O–)]; 2.70–2.76 (m, 2H, –CH2CH3);
4.01 [t, 2H, –COOCH2(CH2)4CH2O–)]; 4.15 [t, 2H, –COOCH2(CH2)4CH2O–)]; 5.85–5.88
and 6.43–6.48 (m, 2H, CH2 =); 6.13–6.18 (m, 1H, CH2 = CH–); 7.00–8.19 (m, 16H, Ar–H).
... -(-(-(Acryloyloxy)ethoxy)benzoyloxy)phenyl-ꢀ-pentylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/2). White solid was
−1
=
=
obtained. Yield: 63%. FT-IR (KBr, cm ): 3035 ( C–H); 2953, 2828 (–CH2–); 1735 (C O);
1
=
– –
1639 (C C); 1605, 1583 (Ar–); 1254 (C O C). H-NMR (CDCl3, TMS, δ, ppm): 0.91–
1.71 [m, 9H, –CH2(CH2)3CH3)]; 2.68–2.72 [t, 2H, –CH2(CH2)3CH3)]; 4.32–4.58 [m, 4H, –
COO(CH2)2O–)]; 5.85–5.90 and 6.45–6.49 (m, 2H, CH2 =); 6.17–6.21 (m, 1H, CH2 = CH–);
7.02–8.18 (m, 12H, Ar–H).

MOL. CRYST. LIQ. CRYST.
5
... -(-(-(Acryloyloxy)hexyloxy)benzoyloxy)phenyl-ꢀ-pentylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/2). White solid was
−1
=
=
obtained. Yield: 45%. FT-IR (KBr, cm ): 3031 ( C–H); 2932, 2858 (–CH2–); 1732 (C O);
1
=
– –
1639 (C C); 1606, 1580 (Ar–); 1273 (C O C). H-NMR (CDCl3, TMS, δ, ppm): 0.90–
0.94 (m, 3H, –CH3); 1.35–1.85 [m, 14H, –CH2(CH2)3CH3) and –COOCH2(CH2)4CH2O–)];
2.69–2.72 [t, 2H, –CH2(CH2)3CH3)]; 4.02 [t, 2H, –COOCH2(CH2)4CH2O–)]; 4.17 [t, 2H, –
COOCH2(CH2)4CH2O–)]; 5.85–5.89 and 6.43–6.48 (m, 2H, CH2 =); 6.15–6.20 (m, 1H, CH2
= CH–); 7.01–8.18 (m, 12H, Ar–H).
... -(-(-(Acryloyloxy)ethoxy)benzoyloxy)biphenyl-ꢀ-pentylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/1). White solid was
−1
=
obtained. Yield: 57%. FT-IR (KBr, cm ): 3071 ( C–H); 2955, 2854 (–CH2–); 1732, 1723
1
=
=
– –
(C O); 1640 (C C); 1601, 1571 (Ar–); 1276 (C O C). H-NMR (CDCl3, TMS, δ, ppm):
0.90–1.71 [m, 9H, –CH2(CH2)3CH3)]; 2.70–2.73 [t, 2H, –CH2(CH2)3CH3)]; 4.33–4.58 [m,
4H, –COO(CH2)2O–)]; 5.84–5.90 and 6.46–6.51 (m, 2H, CH2 =); 6.17–6.22 (m, 1H, CH2 =
CH–); 7.02–8.20 (m, 16H, Ar–H).
... -(-(-(Acryloyloxy)hexyloxy)benzoyloxy)biphenyl-ꢀ-pentylbenzoate (M)
Purified by silica gel column chromatography (ethyl acetate/hexane = 1/2). White solid was
−1
=
=
obtained. Yield: 63%. FT-IR (KBr, cm ): 3056 ( C–H); 2956, 2829 (–CH2–); 1732 (C O);
1
=
– –
1636 (C C); 1604, 1578 (Ar–); 1276 (C O C). H-NMR (CDCl3, TMS, δ, ppm): 0.91–
0.93 (m, 3H, –CH3); 1.34–1.86 [m, 14H, –CH2(CH2)3CH3) and –COOCH2(CH2)4CH2O–)];
2.70–2.73 [t, 2H, –CH2(CH2)3CH3)]; 4.05 [t, 2H, –COOCH2(CH2)4CH2O–)]; 4.18 [t, 2H, –
COOCH2(CH2)4CH2O–)]; 5.84–5.89 and 6.42–6.47 (m, 2H, CH2 =); 6.16–6.20 (m, 1H, CH2
= CH–); 7.03–8.21 (m, 16H, Ar–H).
2.5. Synthesis of the polymers
The synthetic route of the polymers P1−P8 is shown in Scheme 2. The yields and average
molecular weight of P1−P8 are summarized in Table 1. The eight polymers were prepared by
the radical polymerization of monomers in a sealed ampoule tube with anhydrous toluene
using azobisisobutyronitrile (AIBN, 3 mol% to the monomer) as an initiator at 60°C for 24
hr under nitrogen conditions. The crude polymers were precipitated in a large amount of
methanol solution, and then purified by dissolving them in toluene and reprecipitated in
methanol, and then dried in a vacuum.
Scheme . Synthesis of the polymers P1−P8.

6
X.-X. XU ET AL.
Table . Yields and average molecular weights of polymers.
Polymer
Yield/ %
Mn(× g/mol)
Mw(× g/mol)
PDI
P








.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
P
P
P
P
P
P
P
.
aData determined by GPC in THF using PS standards.
bPDI = Mw/ Mn, dispersion coefficient.
3. Results and discussion
3.1. Mesomorphism of the monomers
The mesomorphism of the monomers was characterized with POM and DSC. POM results
showed that M1−M8 exhibited enantiotropic nematic a thread-like Schlieren texture on heat-
ing and cooling cycles. As an example, the optical textures of M1 are shown in Fig. 1. Table 2
summarizes the phase transition temperatures, enthalpy changes and mesophase types of
M1−M8. On heating cycle, eight monomers all showed a melting transition at low tempera-
ture, only M1, M2, M4, M5, and M6 revealed an obvious nematic to isotropic phase transition
at high temperature. On cooling cycle, an isotropic to nematic phase transition except for
M3, M7, and M8, and a crystallization transition for all the monomers appeared. However,
POM results confirmed that M3, M7, and M8 exhibited excellent mesomorphism and typi-
cal nematic texture. Therefore, the isotropic temperatures (Ti) of M3, M7, and M8, listed in
Table 2, were obtained with POM. According to Table 2, the molecular structure had a con-
siderable influence on the thermal behavior of M1−M8. The effect of the spacer length, meso-
genic core rigidity, and terminal group on the melting temperature (Tm) and Ti was discussed
in detail as follows.
... The effect of the spacer length
In general, with increasing the spacer length, the intermolecular forces weaken, which make
the thermal behavior change, and the phase transition temperatures decrease. For example,
M1 and M2 had same mesogenic core and terminal groups, but the spacer length was different.
Compared with M1 containing two methylene spacers, Tm and Ti of M2 containing six methy-
lene spacer decreased by 37.3 and 1.3°C, respectively. Similarly, Tm and Ti of M4 decreased by
54.5 and 3.7°C than those of M3; Tm and Ti of M6 decreased by 55.9 and 9.9°C than those of
M5; Tm and Ti of M8 decreased by 36.1 and 15.0°C than those of M7. According to the above
data, with increasing the spacer length, the corresponding Tm and Ti all decreased, moreover,
the Tm decreased more than Ti, so the mesophase temperature range widened.
... The effect of the mesogenic core rigidity
With increasing the rigidity of the mesogenic core or the number of aryl rings in LC molecules,
the corresponding Tm and Ti increased. Taking the effect of the number of aryl rings on Ti
into account, the equation is given by Dejeu [26] as follows:
0.084(α// − α⊥)I
T =
i
(1)
KV2

MOL. CRYST. LIQ. CRYST.
7
Figure . Optical textures of M1 (×). (a) thread-like texture of nematic phase; (b) Schlieren texture of
nematic phase.
Where K is Boltzman’s constant, I is ionized electric potential, V is molar volume, and
α// − α⊥ is polarizability anisotropy parallel and normal to molecular axis direction. In the
conjugate system of the aryl rings, the α//-value is very great, so the α//-value will increase
with increasing the number of the aryl rings, and Ti also increases. For example, M1 and M3
had same spacer length and terminal groups, but the mesogenic core was different. Compared
Table . Phase transition temperature (°C) and enthalpy changes (J·g−) of the monomers.
Monomer
Mesophase and phase transitions/ Heating/Cooling
M
M
M
M
M
M
M
M
Cr.(.)N.(.)I
Cr.(.)N.(.)I
Cr.(.)N.aI
Cr.(.)N.(.)I
Cr.(.)N.(.)I
Cr.(.)N.(.)I
Cr.(.)N.aI
Cr.(.)N.aI
I.(.)N.(.)Cr
I.(.)N.(.)Cr
.aN.(.)Cr
I.(.)N.(.)Cr
I.(.)N.(.)Cr
I.(.)N.(.)Cr
I.aN.(.)Cr
I.aN.(.)Cr
Cr = crystal, N = nematic; I = isotropic.
aData obtained by POM.

8
X.-X. XU ET AL.
with M1 containing three phenyl rings in the mesogenic core, Tm and Ti of M3 containing four
phenyl rings increased by 33.8 and 161.4°C, respectively. Similarly, Tm and Ti of M4 increased
by 16.6 and 159.0°C than those of M2; Tm and Ti of M7 increased by 26.5 and 163.9°C than
those of M5; Tm and Ti of M8 increased by 46.3 and 158.8°C than those of M6. According to
the above data, Ti increased more than Tm with an increase of phenyl rings, so the mesophase
temperature ranges widened.
... The effect of the terminal group
The flexibility and polarity of the terminal group also can affect the phase transition temper-
atures. With increasing the flexibility a of the terminal group, the corresponding Tm and Ti
decreased, which also is similar to the effect of the spacer length. For example, M1 and M5
had same spacer length and mesogenic core, but the terminal group was different. Compared
with M1 containing terminal ethyl group, Tm and Ti of M5 containing terminal pentyl group
decreased by 22.3 and 8.3°C, respectively. Similarly, Tm and Ti of M6 decreased by 40.9 and
16.9°C than those of M2; Tm and Ti of M7 decreased by 29.6 and 5.8°C than those of M3; Tm
and Ti of M8 decreased by 11.2 and 17.1°C than those of M4.
3.2. Mesomorphism and thermal properties of the polymers
The mesomorphism of the polymers was investigated with POM and DSC. POM results
showed that P1−P8 exhibited typical nematic thread-like texture on heating and cooling
cycles. As an example, the optical textures of P1 are shown in Fig. 2. Table 3 shows the phase
transition temperatures of P1−P8. As seen from the data listed in table 3, the eight polymers
all showed a melting transition, this indicated they were semi-crystalline polymers. Similar
to the above monomers, chemical structures also affect the phase behavior of P1−P8. More-
over, the same tendency was seen. For example, Tm and Ti of P2 with six methylene spacer
decreased by 24.5 and 17.9°C than those of P1 with two methylene spacer; Tm and Ti of P3
with four phenyl rings in the mesogenic core increased by 35.2 and 109.4°C than those of
P1 with three phenyl rings; Tm and Ti of P5 with terminal pentyl group decreased by 5.3 and
5.9°C than those of P1 with terminal ethyl group. In addition, the mesophase temperature
ranges of P1−P8 were greater than those of the monomers. Such behavior could be attributed
to the polymerization effect.
The thermal stability of the polymers P1−P8 was detected with TGA. The corresponding
thermal decomposition data are listed in Table 3. The temperatures at which 5 % weight loss
occurred (Td) of P1−P8 were above 330°C, this indicated that they had high thermal stability
under the nitrogen atmosphere.
Table . The phase transition temperatures and decomposition temperatures of polymers.
Polymer
Tg (°C)
Tm (°C)
Ti (°C)
Tdb (°C)
P
.
—
.
—
—
—
.
.
.








P
P
P
P
P
P
P
.
.
.
.
.
.
.
.a
.a
.
.
—
—
.a
.a
aData obtained by POM;
bTemperature at which % weight loss occurred.

MOL. CRYST. LIQ. CRYST.
9
Figure . Optical textures of P1 (×). (a) thread-like texture of nematic phase; (b) thread-like texture of
nematic phase.
4. Conclusions
Eight new LC monomers and polymers were synthesized and characterized. M1−M8 all
showed enantiotropic nematic thread-like texture and schlieren texture; P1−P8 all exhib-
ited nematic thread-like texture. The experimental results demonstrated that the Tm and
Ti of eight monomers and corresponding polymers all decreased with increasing the spacer
length or flexibility of the terminal group, however, their Tm and Ti all increased with increas-
ing the rigidity of the mesogenic core. The Td of all the obtained polymers was greater
than 335°C.
Acknowledgments
The authors are grateful to Science and Technology Committee of Liaoning Province (2013020103) and
Science and Technology Bureau of Shenyang (F14-231-1-05) for financial support of this work.

10
X.-X. XU ET AL.
References
[1] Lee, J. D., & Eringen, A. C. (1974). In Liquid Crystals and Ordered Fluids; Johnson, J. F., & Porter,
R. S., (Eds.), Plenum: New York, NY.
[2] Trokhymchuk, A. (2010). Condens. Matter. Phys., 13, 370021.
[3] Lee, M., Choi, B. K., & Zin, W. C. (2001). Chem. Rev., 101, 3869.
[4] Tschierske, C. (2002). Curr. Opin. Colloid In., 7, 69.
[5] Pauluth, D., & Tarumi, K. J. (2004). Mater. Chem., 14, 1219.
[6] Goodby, J. W., Saez, I. M., Cowling, S. J., Görtz, V., Draper, M., Hall, A. W., Sia, S., Cosquer, G.,
Lee, S. E., & Raynes, E. P. (2008). Angew. Chem., 47, 2754.
[7] Keizer, S. H. M., & Sijbesma, R. P. (2005). Chem. Soc. Rev., 34, 226.
[8] Le Barney, P., Dubois, J. C., Friedrich, C., & Noel, C. (1986). Polym. Bull., 15, 341.
[9] Hsu, C. S., & Percec, V. J. (1989). Polym. Sci. Polym. Chem. Ed., 27, 453.
[10] Hsiech, C. J., Wu, S. H., Hsiue, G. H., & Hsu, C. S. (1994). J. Polym. Sci. Part A: Polym. Chem., 32,
1077.
[11] Wu, Y. H., Lu, Y. H., & Hsu, C. S. (1995). J. Macromol. Sci. A, 32, 1471.
[12] Hu, J. S., Zhang, B. Y., Pan, W., & Zhou, A. J. (2005). Liq. Cryst., 32, 441.
[13] Liu, J. H., & Yang, P. C. (2006). Polymer, 47, 4925.
[14] Hu, J. S., Li, D., Zhang, W. C., & Meng, Q. B. (2012). J. Polym. Sci. Part A: Polym. Chem., 50, 5049.
[15] Hu, J. S., Li, Q., Liu, Y. N., Song, Y. T., & Li, W. (2013). Liq. Cryst., 40, 1095.
[16] Brettar, J., Burgi, T., Donnio, B., Guillon, D., Klappert, R., Scharf, T., & Deschenaux, R. (2006).
Adv. Funct. Mater., 16, 260.
[17] Hammond, M. R., & Mezzenga, R. (2008). Soft Matter., 4, 952.
[18] Liu, J. H., Wang, Y. K., Chen, C. C., Yang, P. C., Hsieh, F. M., & Chiu, Y. K. (2008). Polymer 49,
3938.
[19] Yang, S. H., & Hsu, C. S. (2009). J. Polym. Sci. Part A: Polym. Chem., 47, 2713.
[20] Serra, F., Matranga, M. A., Ji, Y., & Terentjev, E. M. (2010). Opt. Express, 18, 575.
[21] Ohm, C., Haberkorn, N., Theato, P., & Zentel, R. (2011). Small, 7, 194.
[22] Wang, A., Kawabata, K., & Goto, H. Materials, 6, 2218.
[23] Portugall, M., Ringsdorf, H., & Zentel, R. (1982). Makromol. Chem., 183, 2311.
[24] Mihata, T., Nomura, K., Funaki, K., & Koide, N. (1997). Polym. J., 29, 303.
[25] Hu, J. S., Zhang, B. Y., Jia, Y. G., & Wang, Y. (2003). Polym. J., 35, 160.
[26] Dejeu, W. H. (1977). Mol. Cryst. Liq. Cryst., 40, 1.