Investigation of thermodynamic properties of 4-decyloxybiphenyl-4′-carboxylic acid liquid crystal and preparation of polymer dispersed liquid crystal composite

Article abstract of DOI:10.1016/j.molliq.2018.05.080

In this study, firstly, retention behavior of solvents on the liquid crystalline material 4-decyloxybiphenyl-4′-carboxylic acid (DBCA) has been studied by inverse gas chromatography (IGC) technique. Liquid crystal (LC) selectivity was investigated using t

Full text of DOI:10.1016/j.molliq.2018.05.080

Accepted Manuscript
Investigation
-decyloxybiphenyl-4′-carboxylic acid liquid crystal and
preparation of polymer dispersed liquid crystal composite
of
thermodynamic
properties
of
4
Emine Öztürk, Hale Ocak, Fatih Cakar, Gürkan Karanlık, Özlem
Cankurtaran, Belkis Bilgin-Eran
PII:
S0167-7322(18)31086-9
doi:10.1016/j.molliq.2018.05.080
MOLLIQ 9135
DOI:
Reference:
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
5 March 2018
16 May 2018
19 May 2018
Please cite this article as: Emine Öztürk, Hale Ocak, Fatih Cakar, Gürkan Karanlık,
Özlem Cankurtaran, Belkis Bilgin-Eran , Investigation of thermodynamic properties of
4
-decyloxybiphenyl-4′-carboxylic acid liquid crystal and preparation of polymer dispersed
liquid crystal composite. The address for the corresponding author was captured as
affiliation for all authors. Please check if appropriate. Molliq(2017), doi:10.1016/
j.molliq.2018.05.080
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ACCEPTED MANUSCRIPT
INVESTIGATION OF THERMODYNAMIC PROPERTIES OF 4-
DECYLOXYBIPHENYL-4’-CARBOXYLIC ACID LIQUID CRYSTAL
AND PREPARATION OF POLYMER DISPERSED LIQUID CRYSTAL
COMPOSITE
Emine Öztürk, Hale Ocak, Fatih Cakar, Gürkan Karanlık, Özlem Cankurtaran*, Belkis Bilgin-Eran
Department of Chemistry, Yildiz Technical University, Istanbul, Turkey
ABSTRACT
In this study, firstly, retention behavior of solvents on the liquid crystalline material 4-
decyloxybiphenyl-4’-carboxylic acid (DBCA) have been studied by inverse gas
chromatography (IGC) technique. Liquid crystal (LC) selectivity was investigated using the
acetate isomers by the IGC method at temperatures between 333.2 K and 543.2 K. Later on,
the interactions of LC with n-octane, n-nonane, n-decane, undecane, dodecane, tridecane, n-
propyl benzene, isopropyl benzene, ethylbenzene, chlorobenzene and toluene between 518.2
K and 543.2 K were examined. LC-solvent interaction parameters for Flory-Huggins theory,
∞
∗
12
휒 , and equation of state theory, 휒 , effective exchange energy parameters, 푋푒푓푓, the weight
1
2
∞
1
fraction activity coefficent, Ω , the partial molar heat of mixing at infinite dilution of the
∞
1
solvent, ∆퐻 , molar heat of vaporization of solvent, ∆퐻 and the partial molar heat of
푉
sorption of the solvent, ∆퐻1,푠 were obtained.
Secondly, polymer dispersed liquid crystal (PDLC) composite film in composition 20/80
poly(methyl methacrylate) (PMMA):DBCA by weight was synthesized by solvent-induced
phase separation method. The mesomorphic behaviour of DBCA and PDLC composite has
been investigated by differential scanning calorimetry (DSC) and optical polarizing
microscopy (PM).
Key words: Liquid crystal, Thermodynamic interaction parameters, Inverse gas
chromatography, Poly(methyl methacrylate), Polymer dispersed liquid crystal composite

ACCEPTED MANUSCRIPT
1
.Introduction
Liquid crystals (LCs) are attractive organic functional materials that exhibit both fluidity and
molecular alignment. They have a great potential to obtain high performance materials which
can be applied for information and communication technologies [1-3]. Shape anisotropy,
dipole–dipole interaction, microphase segregation and non-covalent interactions are the most
fundamental factors in designing LC materials exhibiting the desired mesophase behaviour
and excellent performance in electro-optic display technologies [4]. Among many kinds of LC
materials with different molecular structures, rod-shape (calamitic LCs) materials are widely
used in a flat-panel display, switchable windows, laser and other photonics. For such materials
smectic phases are observed in most cases. Some characteristics of LCs such as low viscosity,
high photochemical and thermal stability, high dielectric biaxiality and a wide range of the
smectic C phase are required for useful applications [5-7].
Inverse gas chromatography (IGC) is a simple, fast and accurate method for investigating the
physicochemical properties such as solubility and thermodynamic interaction parameters of
non-volatile materials, including polymers, polymer blends, LCs, etc. [8-11]. The application
of LCs as stationary phases in gas chromatography was reported by Kelker [8-10], and Dewar
and Schroeder [11, 12]. It was known that LCs have shown this particular selectivity and
sensitivity as stationary phases for the separation of isomers. While the determination of
isomeric solvents by ordinary stationary phases offered some difficulties, these isomers have
similar boiling points and polarities; a search for better stationary phases including highly
selective ones was an important trend of gas chromatography (GC) development. The
solubility data of a LC in some probes might be required for design of novel applications. The
interaction between a LC and a probe is generally investigated by the value of Flory-Huggins
interaction parameter [13-15].
Polymer dispersed liquid crystals (PDLCs) have a great interest as advanced functional
materials for a wide variety of electrooptic applications ranging from windows shutters to
projection displays, optical information storage devices [16]. PDLCs, in which LC droplets
are dispersed in a polymer matrix, can be applied in various industrial fields, such as smart
windows, light shutters, high resolution displays and projection light valves a so forth [17].
PDLCs have been suggested to avoid the flow of LCs, to increase the mechanical stability and
to facilitate the fabrication process. Moreover, their light transmittance is much higher than
conventional LC displays due to the absence of a polarizer [18, 19]. Various techniques such
as solvent-induced phase separation (SIPS), polymerization-induced phase separation (PIPS)
and thermally-induced phase separation (TIPS) method are being used to form droplets of the

ACCEPTED MANUSCRIPT
LCs in the polymer matrix and prepare PDLC composite films. Solvent evaporation rate plays
an important role in the formulation structure of the PDLC films in SIPS method, where the
LC and the polymer are dissolved in a common solvent to obtain a single phase [20]. In this
method is generally used transparent thermoplastic polymers such as poly(methyl
methacrylate) (PMMA).
In this study, firstly we synthesized and characterized a new LC 4-Decyloxybiphenyl-4’-
carboxylic acid (DBCA). The selectivity of the DBCA was investigated by using n-butyl
acetate, tert-butyl acetate and iso-butyl acetate at temperatures between 333.2 K and 543.2 K,
and then, thermodynamic interactions were determined using n-butyl acetate, iso-butyl
acetate, n-octane, n-nonane, n-decane, undecane, dodecane, tridecane, n-propyl benzene,
isopropylbenzene, ethylbenzene, chlorobenzene and toluene at temperatures between 518.2 K
and 543.2 K by IGC technique. Subsequently, we synthesized PDLC composite by SIPS
method. PMMA and DBCA were controlled to be 20/80 wt%.
2
. Theory of thermodynamic characterization by IGC technique
IGC at infinite dilution is used to characterize the thermodynamic characteristics of LCs [13-
0
푔
1
5]. The specific retention volume ꢀ was calculated from [21-22]
0
ꢀ
= ꢁ73.ꢁ 푄(푡 − 푡 )퐽/(푇 푤)
(1)
푔
푅
퐴
푓
where Q is the carrier gas flow rate measured at room temperature 푇 ; 푡 and 푡 are retention
푓
푅
퐴
times of the solvent and air, respectively; w is the weight of LC in the column,
J
is the
pressure correction factor, which depends on the inlet pressure 푃 , and outlet pressure 푃 ,
푖
0
calculated using the following relation,
2
3
퐽 = ⌊
ꢁ
(푃 ⁄푃 ) − ꢂ
푖
0
⌋
(ꢁ)
ꢃ
(푃 ⁄푃 ) − ꢂ
푖
0
The interaction between two components in a mixture can be evaluated by Flory-Huggins
∞
∗
12
interaction parameters, 휒12 and 휒 from following equations, respectively:
ꢀ10
0
0
ꢁ
73.ꢁꢅ푣2
푝 (퐵 − ꢀ )
1 1
11
∞
휒 = 푙푛 ꢄ
ꢆ − ꢄꢂ −
∗
ꢆ −
(3)
1
2
0
0
푔
푝 ꢀ ꢀ
1
푀2푣2
ꢅ푇
1

ACCEPTED MANUSCRIPT
ꢁ
73.ꢁꢅ푣2∗
ꢀ1∗
∗ꢆ −
푀2푣2
푝 (퐵 − ꢀ )
0
1
0
1
11
∗
휒 = 푙푛 ꢄ
ꢆ − ꢄꢂ −
∗
(4)
1
2
0
0
푔
푝 ꢀ ꢀ
1
ꢅ푇
1
0
1
0
1
where, R is the universal gas constant, ꢀ , 퐵 and 푝 are the molar volume, the second
11
virial coefficient and the saturated vapor pressure of the solvent at temperature T,
∗
1
∗
2
respectively, ꢀ is the molar hard-core volume of the solvent, 푣 and 푣 are specific volume
2
and specific hardcore volume of the liquid crystal, respectively.
The effective exchange energy parameter, 푋푒푓푓, in the equation of state theory is calculated as
follows:
1
1푟
/ꢃ
1/ꢃ
ꢅ푇휒 = 푝 ꢀ {3푇 푙푛[(푣 − ꢂ)/(푣2푟 − ꢂ)] + 푣 1ꢇ 푟1 − 푣 + 푋푒푓푓/푃 푣 }
∗
∗
∗
ꢇ1
∗
(5)
1
2
1 1
1푟
2푟
1
2푟
∗
1
푝 is characteristic pressure, 푣 and 푣 are reduced volume of the solvent and LC,
1푟
2푟
respectively. 푇 is reduced temperature of the solvent.
1푟
∞
The weight fraction activity coefficent, Ω1 has become the most widely used parameter in
∞
IGC method compared to the 휒12 in terms of thermodynamic interactions since it is derived
from the fundamental relations of physical chemistry and consequently does not include any
uncertainty coming from the theoretical assumptions and can be calculated from
chromatographic data using the molar mass of the probe.
∞
1
Ω is the weight fraction activity coefficient of solvent at infinite dilution is defined by the
following equation [23]:
0
0
ꢁ
73.ꢁꢅ
푝 (퐵 − ꢀ )
1 1
11
∞
Ω = 푙푛 ꢄ
ꢆ −
(6)
1
0 0
ꢀ
푝 푀
1
ꢅ푇
푔
1
Where 푀 is the molecular weight of solvent.
1
∞
1
The partial molar heat of mixing, ∆퐻 , is obtained from equation [24-26]
∞
휕(푙푛Ω )
1
∞
∆
퐻 = ꢅ ꢈ
ꢉ
(7)
1
휕(ꢂ/푇)
The partial molar heat of sorption, ∆퐻 , of the solvent sorbed by the solute is given as:
1,푠
0
휕ꢊ푙푛ꢀ ꢋ
푔
∆
퐻1,푠 = −ꢅ ꢈ
ꢉ
(8)
휕(ꢂ/푇)

ACCEPTED MANUSCRIPT
The molar heat of vaporization, ∆퐻 , of the solvent is defined as follows:
푉
∞
∆
퐻 = ∆퐻 − ∆퐻
(9)
푉
1
1,푠
3
.Experimental
3
.1.Materials and Instrumentation
A Hewlett-Packard 6890 N gas chromatography with a thermal conductivity detector was
used to research the retention times of the solvents. The column was made of stainless steel
tubing with 3.2 mm outside diameter and 1 m in length, was obtained from Alltech
Associates, Inc. The LC was coated on the support material by slow evaporation of
chloroform as stirring the Chromosorb W in the LC solution. 0.1 휇L of solvent was injected
into the column with a 1 휇L Hamilton syringe and flushed into the air. The column was
conditioned under a helium atmosphere for 24 h at 423.2 K.
1
13
Compound DBCA was characterized H-NMR and C-NMR (Bruker Avance III 500
spectrometer, in DMSO-d solution, with tetramethylsilane as internal standard). The
6
mesomorphic properties of DBCA and PDLC were investigated by using a Mettler FP-82 HT
hot stage and control unit in conjunction with a Leica DM2700P polarizing microscope. DSC-
thermograms of DBCA and PDLC composite films were recorded on a Perkin-Elmer DSC-6,
-1
heating and cooling rate: 10°C min in a nitrogen atmosphere. The rigid and transparent
PMMA was used as a acrylic polymer for PDLC from Alfa Eesar with molecular weight of
M = 120000 (g/mol). Ethyl 4-hydroxy-4-biphenylcarboxylate (Aldrich), n-decyl bromide
w
(
Merck), NaOH (Merck) and K CO (Merck) were purchased commercially. Solvents were
2 3
purchased or distilled. 2-Butanone (Merck) and Ethanol (Merck) were purchased
commercially and were used without further purification. Solvents (chloroform and ethanol)
used in the separation and purification steps were distilled. Analytical thin-layer
chromatography (TLC) was carried out on aluminium plates coated with silica gel 60 F254
(Merck).
In the IGC method, the probes such as n-butyl acetate, tert-butyl acetate, iso-butyl acetate, n-
octane, n-nonane, n-decane, undecane, dodecane, tridecane, n-propylbenzene,
isopropylbenzene, ethylbenzene, chlorobenzene and toluene were used without further
purification as obtained from Merck AG Inc. The support material, Chromosorb-W (AW-
DMCS-treated, 80/100 mesh), was also purchased from Merck AG Inc. Silane-treated glass

ACCEPTED MANUSCRIPT
wool used to plug the ends of the column was supplied from Alltech Associates, Inc. Purity of
reagents and purification method of solvents are given in Table 1.
Table 1. Purity of reagents and purification method
Initial Mole
FractionPurity
Purification
method
Final Mole
FractionPurity Method
Analysis
Chemical Name
Source
ethyl 4-hydroxy-4-
biphenylcarboxylate
n-decyl bromide
sodium hydroxide
potassium carbonate Merck
Aldrich
= 0.980
none
-
-
Merck
Merck
<=1.000
<=1.000
≥ 0.990
≥ 0.990
≥ 0.999
-
none
none
none
none
none
-
-
-
-
-
-
-
-
2
-butanone
Merck
Merck
-
-
-
ethanol
distilation
distilation
none
0.960
0.999
GC*
GC*
chloroform
n-octane
n-nonane
n-decane
undecane
Tekkim
Merck
Merck
Merck
Merck
Merck
Merck
Merck
Merck
Merck
Merck
Merck
-
≥ 0.999
≥ 0.999
≥ 0.999
≥ 0.990
≥ 0.990
≥ 0.990
≥ 0.999
≥ 0.999
≥ 0.999
≥ 0.999
≥ 0.999
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
none
none
none
none
none
none
none
none
dodecane
tridecane
n-propylbenzene
isopropylbenzene
ethylbenzene
chlorobenzene
toluene
none
none
*Gas-liquid chromatography
3
.2 Synthesis and Characterization of DBCA
The synthesis of DBCA was carried out according to procedures described in the literature
27]. Firstly, the mixture of Ethyl 4-hydroxy-4-biphenylcarboxylate (6.7 mmol), n-decyl
bromide (10 mmol) and K CO (10 mmol) in 2-Butanone (70 mL) was refluxed under argon
[
2
3
atmosphere for 5 h, and the end of the reaction was monitored by TLC (chloroform). The
resulting mixture was filtered on silica gel and washed with chloroform. The solvent was
removed under reduced pressure. The resulting product Ethyl 4-(n-decyloxy)biphenyl-4′-
carboxylate (EDBC) was purified by crystallization from ethanol. Yield: 92%; colorless
1
crystals. H-NMR: (500 MHz, DMSO-d ): δ (ppm) = 8.11 (d, J ≈ 8.4 Hz; 2H, 2 Ar-H), 7.64
6
(d, J ≈ 8.4 Hz; 2H, 2 Ar-H), 7.59 (d, J ≈ 8.7 Hz; 2H, 2 Ar-H), 7.01 (d, J ≈ 8.7 Hz; 2H, 2 Ar-
H), 4.42 (q, J ≈ 7.1 Hz; 2H, COOCH ), 4.03 (t, J ≈ 6.6 Hz; 2H, OCH ), 1.86-1.81 (m; 2H,
2
2
CH ), 1.53-1.47 (m; 2H, CH ), 1.39-1.28 (2m; 12H, 6 CH ), 1.44 (t, J ≈ 7.1 Hz; 3H,
2
2
2
1
3
OCH CH ), 0.91 (t, J ≈ 6.8 Hz; 3H, CH ). C-NMR (125 MHz, DMSO-d ): δ (ppm) =
2
3
3
6
1
66.66 (COOCH CH ), 159.47, 145.24, 132.26, 128.58 (Ar-C), 130.09, 128.35, 126.43,
2 3

ACCEPTED MANUSCRIPT
1
2
14.98 (Ar-CH), 68.20 (OCH ), 60.93 (COOCH CH ), 31.95, 29.63, 29.61, 29.45, 29.37,
2
2
3
9.31, 26.10, 22.73 (CH ), 14.42 (COOCH CH ), 14.16 (CH ).
2
2
3
3
After the etherification reaction of ethyl 4-hydroxy-4-biphenylcarboxylate with the n-decyl
bromide, the hydrolysis was realized to obtain 4-Decyloxybiphenyl-4’-carboxylic acid
(DBCA) [28, 29]. 7.8 mmol of EDBC was dissolved in 60 mL of EtOH and added 15.6 mmol
of NaOH solution to this mixture. The mixture was heated under the reflux for 12 h. The
result of the reaction was monitored by TLC (chloroform). Then, the hot solution was poured
into the water and the pH adjusted between 1-2 by adding 1 N HCl. The resulting crude
1
product was filtered and crystallized from ethanol. Yield: 72%; colorless crystals. H-NMR:
(
500 MHz, DMSO-d ): δ (ppm) = 7.97 (d, J ≈ 8.3 Hz; 2H, 2 Ar-H), 7.72 (d, J ≈ 8.3 Hz; 2H, 2
6
Ar-H), 7.67 (d, J ≈ 8.7 Hz; 2H, 2 Ar-H), 7.04 (d, J ≈ 8.7 Hz; 2H, 2 Ar-H), 4.02 (t, J ≈ 6.5 Hz;
H, OCH ), 1.76-1.71, 1.48-1.39, 1.35-1.25 (3m; 16H, 8 CH ), 0.86 (t, J ≈ 6.8 Hz; 3H, CH ).
2
2
2
3
1
3
C-NMR (125 MHz, DMSO-d ): δ (ppm) = 167.20 (COOH), 158.96, 143.83, 131.08, 129.05
6
(
Ar-C), 129.89, 128.06, 126.01, 114.96 (Ar-CH), 67.52 (OCH ), 31.26, 28.97, 28.92, 28.73,
2
2
8.66, 28.62, 25.46, 22.06 (CH ), 13.92 (CH ).
2
3
3
.3. Preparation of PDLC Composite
In this study, PDLC composite of PMMA and DBCA were prepared by SIPS method. We
mixed appropriate amounts of PMMA and DBCA in a common solvent (DMSO), this
solution was stirred mechanically until glass transition temperature for 30 minutes and then
mixture was dried at 50 °C under vacuum in order to induce the phase separation of LC
droplets from the polymer matrix. PDLC composite (PMMA:DBCA) were controlled to be
2
0:80 wt% [17-20].
4
4
.Result and Discussion
.1.Liquid Crystalline Properties
The mesomorphic properties of the DBCA were investigated by using PM and DSC. The
phase transition temperatures, corresponding enthalpy values and mesophase type observed
for DBCA are given in Figure 1.

ACCEPTED MANUSCRIPT
Figure 1. The chemical structure, mesophase type and phase transition temperatures of the
DBCA.
O
H C O
21
10
OH
a
Compound
T/K [ΔH kJ/mol]
Heating: Cr 363.7 [5.2] Cr 437.9 [7.1] Cr 443.9 [23.8] SmC 515.6 [38.0] Iso
1
2
3
b
DBCA
Cooling: Iso 511.8 [28.6] SmC 437.2 [20.3] Cr 425.6 [1.4] Cr 352.9 [4.3] Cr
1
3
2
a
nd
Perkin-Elmer DSC-6; enthalpy values in italics in brackets taken from the 2 heating and
-1
cooling scans at a rate of 10°C min ; Abbrevations: Cr = crystalline, Sm = smectic, Iso =
isotropic liquid phase.
b
In ref. 29 for compound DBCA: Cr 445.7 SmX 529.7 N 530.2 Iso.
DBCA shows an enantiotropic SmC phase with a Schlieren texture at high temperature as
shown in Figure 2. Transition temperatures were detected by calorimetric peaks of the DSC
heating-cooling scans (see Figure 6 and 7).
Figure 2. The Schlieren texture obtained between crossed polarizers as observed for SmC
phase of DBCA at T= 493.2 K on cooling.
4
.2 Thermodynamic interaction results
The specific retention volume data is necessary in the determination of the thermodynamic
0
푔
properties of a LC by IGC. The specific retention volumes, ꢀ , of the isomeric solvents such
as nBAc, iBAc, tBAc on the DBCA were obtained from IGC measurements between 333.2 K
0
푔
and 543.2 K. The percent error in ꢀ was calculated as less than ±0.5 by using four or five

ACCEPTED MANUSCRIPT
successive measurements of each datum. Retention diagrams are plotted in Figure 3 for
0
푔
acetates of DBCA in terms of a plot of 푙푛ꢀ calculated from Equation (1) versus temperature.
According to the retention diagram in Figure 3, Cr 1-Cr 2, Cr 2-SmC and SmC-Iso transitions
for DBCA were found to be 358.2 K, 449.2 K and 505.2 K, respectively, in terms of the
maximum points indicated in the majority of the plots. The Cr 1-Cr 2, Cr 2-SmC and SmC-Iso
transition temperatures obtained by IGC technique are in good agreement with the ones
obtained by DSC (Figure 1). As shown in Figure 3, a good separation can be obtained
between isomers in the studied temperature ranges.
4
4
3
3
2
2
1
1
0
0
.5
.0
.5
.0
.5
.0
.5
.0
.5
.0
(
1)
(
2)
(
3)
-
0.5
0
.0018
0.0020
0.0022
0.0024
0.0026
0.0028
0.0030
0.0032
-
1
1
/T (K )
0
푔
Figure 3. The specific retention volume diagrams, ꢀ , of n-butyl acetate (1), iso-butyl acetate
(2) and tert-butyl acetate (3) on DBCA.
Thermodynamic properties of DBCA in liquid state can be studied at thermodynamic
equilibrium region. Linearity is observed when the stationary phase remains in the same
thermodynamic state. Thermodynamic interactions of DBCA were determined at the
temperatures between 518.2 K and 543.2 K because it was found out from Figures 4 and 5
that the thermodynamically equilibrium occurred at this temperature range.

ACCEPTED MANUSCRIPT
3
2
2
1
1
0
0
.0
.5
.0
.5
.0
.5
.0
(
1)
(
2)
(
(
3)
4)
(
(
5)
6)
-
0.5
.00183
0
0.00185
0.00187
0.00189
0.00191
0.00193
0.00195
-
1
1
/T (K )
0
푔
Figure 4. The specific retention volume diagrams, ꢀ , of tridecane (1), dodecane (2),
undecane (3), n-decane (4), n-nonane (5) and n-octane (6) on DBCA
2
1
1
0
0
.0
.5
.0
.5
.0
(
1)
(
2)
(
(
3)
4)
(
5)
-
0.5
.00183
0
0.00185
0.00187
0.00189
0.00191
0.00193
0.00195
-
1
1
/T (K )
0
푔
Figure 5. The specific retention volume diagrams, ꢀ , of n-propyl benzene (1), isopropyl
benzene (2), ethylbenzene (3), chlorobenzene (4) and toluene (5) on DBCA

ACCEPTED MANUSCRIPT
∞
∗
12
The LC-solvent interaction parameters, 휒12 and 휒 determined from Equations (3) and (4)
the values were given in Tables 2 and 3, respectively.
∞
2
The 휒1 higher than 0.5 indicates unfavorable LC-solvent interactions whereas the values
lower than 0.5 remarks favorable interactions in dilute LC solutions. The values of the
obtained parameters are higher than 0.5 and show an increase in the interaction parameter as
∞
∗
12
the temperature is increased. The values of 휒12 and 휒 suggest that all the studied solvents
are poor for DBCA. All of the parameters decrease with temperature indicating exothermic
solubility.
∞
Table 2. Flory-Huggins LC-solvent interaction parameters, 휒 , of DBCA
12
Solvent
518.2 523.2 528.2 533.2 538.2 543.2
n-octane
n-nonane
n-decane
undecane
dodecane
tridecane
1.22 1.32 1.46 1.58 1.70 1.76
1.38 1.45 1.61 1.71 1.79 1.90
1.47 1.56 1.67 1.77 1.87 1.98
1.57 1.66 1.77 1.87 2.00 2.09
1.60 1.69 1.79 1.90 1.98 2.05
1.67 1.78 1.88 1.98 2.08 2.14
n-propylbenzene 1.14 1.33 1.52 1.65 1.88 2.01
isopropylbenzene 1.13 1.33 1.54 1.77 1.95 2.11
ethylbenzene
chlorobenzene
toluene
1.08 1.24 1.42 1.65 1.82 1.98
1.08 1.28 1.50 1.74 2.04 2.25
0.60 0.80 1.03 1.27 1.58 1.80
∞
Standard uncertainty 푢 is 푢(휒 ) =0.01
12

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∗
Table 3. The equation of state LC-solvent interaction parameters, 휒 , of DBCA
1
2
Solvent
518.2 523.2 528.2 533.2 538.2 543.2
n-octane
n-nonane
n-decane
undecane
dodecane
tridecane
1.40 1.51 1.66 1.78 1.91 1.97
1.53 1.60 1.76 1.87 1.95 2.06
1.59 1.68 1.79 1.89 2.00 2.11
1.67 1.75 1.88 1.98 2.10 2.19
1.68 1.77 1.87 1.98 2.06 2.13
1.73 1.84 1.95 2.04 2.14 2.20
n-propylbenzene 1.29 1.48 1.67 1.81 2.05 2.19
isopropylbenzene 1.29 1.50 1.71 1.95 2.13 2.30
ethylbenzene
chlorobenzene
toluene
1.27 1.43 1.62 1.85 2.02 2.20
1.28 1.48 1.71 1.94 2.25 2.47
0.83 1.04 1.27 1.52 1.84 2.06
∞
Standard uncertainty 푢 is 푢(휒 ) =0.01
12
In this study, the effective exchange energy parameters, 푋푒푓푓, in the equation of state theory
were obtained from Equation (5), and the values were tabulated in Table 4. Small values of
푋푒푓푓 indicate that there are specific interactions between solvents and LC; the higher values
of 푋푒푓푓 define poor solubility. It was seen that the 푋푒푓푓 results of DBCA in all solvents
increased with temperature. It was determined that the values are high and approve the
∞
discussion concerning 휒 .
12

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-3
Table 4. The effective exchange energy parameters, 푋푒푓푓 ( j cm ), of DBCA
Solvent
518.2 523.2 528.2 533.2 538.2 543.2
n-octane
n-nonane
n-decane
undecane
dodecane
tridecane
35.8 41.0 47.9 53.7 60.1 64.1
34.8 38.1 44.5 48.7 52.8 57.6
32.8 36.1 40.3 44.0 48.3 52.5
32.2 35.1 38.2 42.6 46.9 50.0
32.1 34.5 37.6 41.3 43.8 46.2
29.8 33.1 35.7 38.5 41.4 43.2
n-propyl benzene 36.8 45.6 55.0 61.6 73.4 80.4
isopropylbenzene 38.1 48.4 58.5 70.5 80.3 89.1
ethylbenzene
chlorobenzene
toluene
42.2 51.7 62.5 75.7 85.9 96.3
53.7 67.9 83.0 100.0 120.9 136.4
23.8 37.8 53.1 69.7 90.9 106.3
-3
Standard uncertainty 푢 is 푢ꢊ푋푒푓푓ꢋ =1.0 ( j cm )
∞
1
The weight fraction activity coefficients of the studied solvents at infinite dilution, Ω , were
detected from Equation (6) and the results were given in Table 5. According to Guillet [30],
∞
1
∞
1
the solvent is good if Ω < 5 but it is poor if Ω > 10. The values between 5 and 10 show
∞
1
moderately good solubility. The values of the Ω parameters suggest that n-alkanes are poor
however benzenes are slightly poor solvents for DBCA.

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∞
1
Table 5. The weight fraction activity coefficients at infinite dilution of the solvents, Ω , of
DBCA.
Solvent
518.2 523.2 528.2 533.2 538.2 543.2
n-octane
n-nonane
n-decane
undecane
dodecane
tridecane
9.5 10.7 12.4 14.0 15.9 17.0
10.1 10.9 12.9 14.2 15.8 17.4
10.2 11.2 12.5 13.8 15.5 17.2
10.5 11.4 12.8 14.2 16.2 17.7
10.0 10.9 12.1 13.6 14.6 15.8
10.0 11.2 12.4 13.7 15.1 16.0
n-propyl benzene 7.4
isopropylbenzene 7.3
9.0 11.0 12.5 16.0 18.2
9.0 11.0 14.0 16.9 19.9
8.7 10.6 13.3 15.9 18.8
ethylbenzene
chlorobenzene
toluene
7.4
6.1
4.9
7.5
9.4 12.0 16.3 20.3
7.8 10.0 13.7 17.2
6.1
∞
1
Standard uncertainty 푢 is 푢(Ω ) =0.1
∞
1
The values of partial molar heat, ∆퐻 , of mixing at infinite dilution were calculated from the
∞
slopes of the plots of 푙푛Ω1 versus 1/T using Equation (7) in the temperature ranges from
∞
1
5
18.2 K to 543.2 K and were given in Table 6. According to the values of ∆퐻 , the solubility
∞
of LC in all solvents is exothermic and the obtained values of ∆퐻1 confirm the discussion
∞
concerning 휒12 and 푋푒푓푓. As well as the values of the partial molar heat, ∆퐻 , of sorption of
1,푠
0
푔
the solvents on DBCA were found from the slopes of the straight lines of 푙푛ꢀ versus in the
same temperature ranges using Equation (8) and results were given in Table 6. The values of
∆
퐻 for the studied solvents calculated from Equation (9) were also compared to the literature
푉
values [31]. The results for all of the studied solvents were given in Table 6. There is a very
good agreement between ∆퐻 and ∆퐻푉퐿 values for dodecane (boiling point 487.2 K) and
푉
tridecane (boiling point 505.2 K) as reported in Table 6. The boiling points of these two
compounds are very close to studied temperatures. However, for other solutes, the calculated
values of ∆퐻 deviate somewhat at studied temperatures.
푉

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−
1
Table 6. The values of the partial molar heat of sorption, ∆퐻 , (kcal mol ), the partial molar
1,푠
∞
1
−1
heat of mixing at infinite dilution, ∆퐻 (kcal mol ), the molar heat of vaporization, ∆퐻
푉
−
1
(
kcal mol ), of the studied solvents, and the literature values of the molar heat of
−
1
vaporization, ∆퐻푉퐿 (kcal mol ) [31].
Solvent
∆퐻1,푠 ∆퐻 1∞ ∆퐻푉 ∆퐻푉퐿
n-octane
n-nonane
n-decane
undecane
dodecane
tridecane
-19.5 -13.4 6.1
-19.5 -12.3 7.2
-20.0 -11.8 8.2
-21.2 -12.0 9.2
8.2
8.8
9.4
9.9
-20.4 -10.4 10.0 10.4
-21.6 -10.7 10.9 10.9
n-propyl benzene -28.0 -20.2 7.8
isopropylbenzene -30.3 -22.9 7.4
9.1
9.0
8.5
8.7
7.9
ethylbenzene
chlorobenzene -34.2 -27.2 7.0
toluene -34.2 -28.4 5.8
-28.4 -21.4 7.0
4
.3. PDLC Composite Properties
LC:polymer composites have a wide variety of promising applications ranging from LC
displays to smart windows and projection light valves [32]. Due to their numerous and
important properties for a wide variety of applications, we prepared PDLC in the ratio 20/80
(wt% LC) by SIPS method. The thermotropic behavior of polymer dispersed LC composite
was investigated by PM and DSC. Comparison of the mesomorphic properties of the DBCA
with the PDLC composite film show that the both LC materials exhibit SmC mesophase in a
wide temperature range. The melting and crystallization points of the PDLC composite
closely resemble to that of the DBCA. DSC thermograms of DBCA and PDLC on heating and
cooling were shown in Figure 6 and 7, respectively.

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(
1)
3
62.2 380.0
4
96.5
4
41.6
(
2)
3
63.7
4
37.9
5
15.6
4
43.9
3
00.0
350.0
400.0
450.0
500.0
550.0
Temperature (K)
Figure 6. DSC thermograms of PDLC (1) and DBCA (2) during the heating process
4
35.1
3
54.6 363.9
3
81.0
4
79.3
(
1)
4
37.2
5
11.8
3
52.9
4
25.6
(
2)
3
00.0
350.0
400.0
450.0
500.0
550.0
Temperature (K)
Figure 7. DSC thermograms of PDLC (1) and DBCA (2) during the cooling process

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The phase transition temperatures on second heating of LC and PDLC were observed at 443.9
K, 515.6 K and 441.6 K, 496.5 K, respectively. The phase transition temperatures on second
cooling of LC and PDLC were observed at 437.2 K, 511.8 K and 435.1 K, 479.3 K,
respectively. In case of the PDLC composite, the clearing temperature (Tc) of the LC phase
was shifted to a lower temperature and the sharp peak became broader in the DSC heating and
cooling curves
Phase transition temperatures as well as morphology of the PDLC composite was examined
by PM. The texture of the PDLC sample was given in Figure 8.
Figure 8. The mesophase texture of PDLC below 479.2 K on cooling.
The mesophase transition temperatures observed in DSC study of PMMA:DBCA composite
on heating and cooling were confirmed with polarized optical microscopy. According to the
PM results, the birefringent regions of DBCA in the composition PMMA:DBCA (20/80) also
appear in PMMA-rich domains on heating and cooling. The existence of the smectic phase in
PMMA:DBCA composite material was illustrated in Figure 8. The Schlieren texture of SmC
mesophase was observed until 434.2 K on cooling and the birefringent texture of mesophase
starts decomposing as the temperature is reduced further (Figure 9) and the isotropic-smectic
phase transition occurs at lower temperature as compared to pure DBCA. As seen in textures,
the LC droplets with spherical shape were not observed on cooling from the isotropic liquid;
however DBCA molecules are partially dispersed in the polymer matrix.

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(a)
(b)
Figure 9. Optical microscopic images under polarized light for PDLC on cooling (a) at 418.2
K and (b) 386.2 K.
Conclusions
In this study, we reported the synthesis and characterization of DBCA exhibiting an
enantiotropic SmC mesophase in a wide temperature range. The phase behaviour of DBCA
was investigated by PM, DSC and IGC. The phase transition temperatures of DBCA obtained
by IGC are good agreement with ones obtained by DSC. The study also suggests that the
seperation ability of the DBCA was good enough for acetate isomers in the studied
temperature ranges. The thermodynamic parameters of DBCA were determined via IGC. The
results suggest that selected solvents are poor solvent for the DBCA. IGC is a convenient
method for the characterisation of the thermodynamic and isomer selectivity of LC
compounds.
The PDLC composite was prepared from PMMA and DBCA by SIPS method. The
mesomorphic behavior of PDLC composite has been investigated by DSC and PM. The
reduce in the transition temperatures of DBCA molecules as well as PM textures of the PDLC
composite confirmed that DBCA molecules are partially dispersed in the polymer matrix.
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Graphical abstract

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Highlights




A new chiral calamitic liquid crystal DBCA was studied.
We reported thermodynamic properties of DBCA.
PDLC composite film was synthesized by solvent-induced phase separation method.
DBCA selectivity was investigated using the acetate isomers by the IGC method