A study of the thermodynamical interactions with solvents and surface characterisation of liquid crystalline 5-((S)-3,7-dimethyloctyloxy)-2-[[[4-(dodecyloxy)phenyl]imino]-methyl]phenol by inverse gas chromatography

Article abstract of DOI:10.1016/j.molliq.2016.09.002

An inverse gas chromatography (IGC) study of thermodynamic interactions of a new chiral calamitic liquid crystalline 5-((S)-3,7-Dimethyloctyloxy)-2-[[[4-(dodecyloxy)phenyl]imino]methyl]phenol (DODPIMP) with some solvents was presented. The retention diagrams of the solvents on the DODPIMP were plotted by specific retention volumes, V_g⁰ at temperatures between 373.2 and 393.2?K. The Flory-Huggins interaction parameter, χ₁₂^∞, the weight fraction activity coefficient, Ω₁^∞ and selectivity coefficients, α, of the structural isomers were determined for the DODPIMP liquid crystal. To characterize the surface properties of, retention diagrams of several non-polar and polar solvents on the DODPIMP were plotted by net retention volumes, V_N in the temperature range from 303.2 to 318.2?K. The dispersive surface energy, the thermodynamic adsorption parameters and the acid–base constants of the compound in the crystalline phase were determined. The results indicated a basic character for the surface of DODPIMP at the studied conditions.

Full text of DOI:10.1016/j.molliq.2016.09.002

Journal of Molecular Liquids 223 (2016) 861–867
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
A study of the thermodynamical interactions with solvents and surface
characterisation of liquid crystalline 5-((S)-3,7-dimethyloctyloxy)-
2
-[[[4-(dodecyloxy)phenyl]imino]-methyl]phenol by inverse
gas chromatography
a
b
a
a
a
Hale Ocak , Serap Mutlu-Yanic , Fatih Cakar , Belkis Bilgin-Eran , Dilek Guzeller ,
a
a,
Ferdane Karaman , Ozlem Cankurtaran ⁎
Yildiz Technical University, Department of Chemistry, Davutpasa Campus, 34220 Esenler, Istanbul, Turkey
a
b
Gedik University, Chemistry Technology Programme, Pendik Campus, 34906 Pendik, Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 April 2016
Received in revised form 19 August 2016
Accepted 1 September 2016
Available online 03 September 2016
An inverse gas chromatography (IGC) study of thermodynamic interactions of a new chiral calamitic liquid crys-
talline 5-((S)-3,7-Dimethyloctyloxy)-2-[[[4-(dodecyloxy)phenyl]imino]methyl]phenol (DODPIMP) with some
solvents was presented. The retention diagrams of the solvents on the DODPIMP were plotted by specific reten-
0
∞
tion volumes, V
weight fraction activity coefficient, Ω
for the DODPIMP liquid crystal.
g
at temperatures between 373.2 and 393.2 K. The Flory-Huggins interaction parameter, χ12, the
∞
1
and selectivity coefficients, α, of the structural isomers were determined
Keywords:
Inverse gas chromatography
Liquid crystals
To characterize the surface properties of, retention diagrams of several non-polar and polar solvents on the
DODPIMP were plotted by net retention volumes, V in the temperature range from 303.2 to 318.2 K. The disper-
N
Thermodynamic interaction parameters
Surface properties
sive surface energy, the thermodynamic adsorption parameters and the acid–base constants of the compound in
the crystalline phase were determined. The results indicated a basic character for the surface of DODPIMP at the
studied conditions.
©
2016 Elsevier B.V. All rights reserved.
1
. Introduction
In this study, we reported the synthesis of a new chiral calamitic
LC, 5-((S)-3,7-Dimethyloctyloxy)-2-[[[4-(dodecyloxy)phenyl]imino]
methyl]phenol (DODPIMP) and the data on its thermodynamic interac-
tions, selectivity coefficients, dispersive surface energy and acid–base
properties determined by IGC.
Liquid crystals (LC)'s are finding increasing application in advanced
technologies such as LC displays, fast switching ferroelectric materials,
sensors, high-performance polymers, transporting of electron, ion or
molecule and drug-delivery systems [1–3]. However, it is needed their
thermodynamic characteristics related to their interaction with various
nonmesogenes for the further development of the multicomponent LC
compositions in various technologies. It is not easy to obtain these
data experimentally since LC generally has complex morphologies and
a limited solubility in solvents [4–6]. Fortunately, inverse gas chroma-
tography (IGC) yields valuable information about the thermodynamic
characteristics of a LC. The interaction between a LC and a solvent
2. Inverse gas chromatography
2.1. Thermodynamic characterization
The primary data measured by IGC are the retention times of the sol-
0
vent (probe) and air. Then, specific retention volume, V
g
is determined
(
probe) is usually characterized by the value of Flory-Huggins interac-
from the following [9] equation;
tion parameter [7,8]. On the other hand, LC materials have a great po-
tential in use as isomer-selective stationary phases for gas
chromatography columns. Certainly, IGC studies serve to reveal the se-
lectivity of a LC for the structural isomers.
0
Vg ¼ QðtR−tAÞJ273:2=ðTrwÞ
ð1Þ
r
where Q is the carrier gas flow rate measured at room temperature T ; J
is the pressure correction factor, w is the weight of liquid crystal in the
⁎
Corresponding author.
E-mail address: kurtaran90@yahoo.com (O. Cankurtaran).
column.
http://dx.doi.org/10.1016/j.molliq.2016.09.002
167-7322/© 2016 Elsevier B.V. All rights reserved.
0

862
H. Ocak et al. / Journal of Molecular Liquids 223 (2016) 861–867
D
The interaction between two components in a mixture can be eval-
uated by Flory-Huggins interaction parameters, χ ∞1 2
γ
S
can also be determined by the method proposed by Dorris and
Gray [16] following the Eq. (9);
ꢀ
ꢁ
!
!
2
0
1
0
1
0
1
p
B11−V
ð−ΔGCH
4ðNÞ a
Þ
γ
2
2
73:2Rv2
V
D
S
∞
χ
¼ Ln
− 1−
−
ð2Þ
γ
¼
ð9Þ
1
2
0
0
1
2
2
0
M2v
RT
p V V
2
1
g
CH2 L½CH2ꢀ
0
0
where, V
1
, B11 and p
1
are the molar volume, the second virial coefficient
where,
and the saturated vapor pressure of the solvent, respectively, at temper-
ature T, v is specific volume of the material in the column.
The weight fraction activity coefficient, Ω
should be a more reliable parameter compared to the χ12 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.
ꢄ
ꢅ
VN ðn þ 1Þ
VN ðnÞ
2
ΔGCH ¼ −RTLn
ð10Þ
∞
2
1
given in the following
∞
ΔGCH
adsorption and determined from the slope of a linear line plotted by
RTLnV of n-alkanes against their carbon atom number, n; a[CH is the
cross-sectional area of an adsorbed methylene group (0.06 nm ) and
is the surface energy of a solid material consisting of only meth-
represents the Gibbs free energy of a single methylene group
2
N
2
]
2
ꢀ
ꢁ
ꢀ
ꢁ
∞
1
0
g
0
1
0
1
0
1
Ω
¼ Ln 273:2R=V p M1 −p B11−V =RT
ð3Þ
γ
L[CH ]
2
2
ylene groups given as γL[CH2] (mJ/m ) = 35.6 + 0.058(293.2-T) where T
is the temperature in K.
where; M
.2. The selectivity coefficient
The difference between the retention times of two solvents which
1
is the molecular weight of the solvent.
2
.3.2. Specific surface interactions
The specific component of the free energy of adsorption, −ΔG is re-
A
lated to the solid phase's ability to act as a donor or acceptor toward to
electrons. The difference between the ordinate values of the polar sol-
2
S
are obtained at the same condition determines the selectivity of the sta-
tionary phase [10]. This selectivity is called as selectivity coefficient (or
vent datum point and the n-alkane reference line in the plot of RTLnV
N
D 0.5
against a(γ
L
)
gives the specific component of the surface free energy,
for each solvent at a given temperature. An equation may be
written for this procedure,
separation factor), α which is defined the ratio of (t
R
A
− t ) values of two
S
−
ΔG
A
solvent peaks obtained under the same condition:
ꢂ
ꢃ
0
tRð2Þ−tA
tRð1Þ−tA
V
V
ꢄ
ꢅ
g;2
α ¼ ꢂ
ꢃ¼
ð4Þ
VN;n
VN;ref
S
0
g;1
−ΔGA ¼ RTLn
ð11Þ
The bigger this ratio, the better is the selectivity of the stationary
phase for the solvent pair of the solvents.
where VN,n and VN,ref are the retention volumes of the polar solvent and
the n-alkane which has the same abscissa value in the n-alkane refer-
ence line, respectively.
S
S
S
2
2
.3. Surface characterization [11–13]
ΔG
A
is related to the enthalpy, ΔH
A
and entropy, ΔS
A
of the specific
adsorption:
.3.1. Dispersive surface interactions
The surface energies and acidity/basicity of the solid materials in the
S
A
S
A
S
A
ΔG ¼ ΔH −TΔS
ð12Þ
column can be determined from the net retention volume of the sol-
vents, V
S
N
:
A
ΔH can be determined for each polar probe from the slope by plot-
S
ting ΔG
A
/T against 1/T.
VN ¼ QJðtR−tAÞTc=ðTrÞ
ð5Þ
S
Then, the ΔH
A
data are related to the acidic or the basic character
through the equation:
where T is the column temperature (K). If the IGC experiments are con-
c
ducted at infinite dilution of the solvents, the molar free energy of ad-
sorption, ΔG is related to V according to:
S
A
ꢁ
−
ΔH ¼ KA:DN þ KDAN
ð13Þ
A
N
⁎
where, DN and AN are Gutmann's donor and modified acceptor num-
bers, respectively, whereas K and K are indicators reflecting acidity
ΔGA ¼ −RTLnðVNÞ þ K
where K is a constant for a given column.
The adsorption between a solid surface and solvent vapor is mainly
governed by dispersive (nonpolar) and specific (polar, hydrogen bond-
ð6Þ
A
D
and basicity of the solid surface in the column. The values of DN and
AN are present in the literature [17,18].
∗
Consequently, K
A D
and K can be determined from the slope and in-
S
ing, etc.) interactions [14]. Thus, surface energy of the solid, γ
S
is consid-
tercept, respectively, of the straight line obtained by plotting −ΔH /
A
D
S
∗
⁎
ered to be sum of dispersive, γ
S
and specific, γ
S
components:
AN versus DN/AN . The ratio K
the classification of a surface with respect to acidity-basicity. If K
N1, the surface is considered to be basic, or vice versa.
D A
/K provides an empirical basis for
D
/
D
S
S
γ ¼ γ þ γ
ð7Þ
K
A
S
S
D
γ
S
can be determined by retention data of n-alkanes on the station-
3. Experimental
ary phase in the column since n-alkanes cannot apply any specific inter-
action. Schultz [15] determined the dispersive surface energy from the
3.1. Materials and instrumentation
For synthesis, (S)-(−)-β-citronellol (Aldrich, ≥99.0%, [α]
D 0.5
slope of the straight line between RTLnV
cording to the following equation;
N
and a(γ
L
)
for each probe ac-
2
0-5.3°, hy-
D
drobromic acid (ABCR, 48% aqueous solution), sulfuric acid (Merck, 95–
98%), tetrabutylammonium hydrogensulfate (Sigma-Aldrich, 97%), 4-
ꢂ
ꢃ1=2ꢂ ꢃ1=2
D
S
D
L
−
ΔGA ¼ RTLn ðVNÞ ¼ 2N a γ
γ
þ C
ð8Þ
(
dodecyloxy)aniline (Sigma-Aldrich), potassium hydrogen carbonate
where a is surface area of the solvent molecule, N is Avogadro's number
(Merck) and p-toluenesulfonic acid monohydrate (Merck) were pur-
chased commercially. Solvents were purchased or distilled. MeOH
and C is constant.

H. Ocak et al. / Journal of Molecular Liquids 223 (2016) 861–867
863
(
Merck), DMF (Merck) and Toluene (Merck) were purchased commer-
(dodecyloxy)aniline in toluene using p-toluene sulfonic acid
monohydrate as catalyst yield the final compound DODPIMP.
The characterization of the DODPIMP is based on 1H NMR and
cially and used without further purification. Analytical thin-layer chro-
matography (TLC) was carried out on aluminum plates coated with
silica gel 60F254 (Merck).
APT-13C NMR (Bruker Avance III 500 spectrometer in CDCl
solutions,
3
n-Hexane (Hx), n-heptane (Hp), n-octane (O), n-nonane (N) and n-
decane (D), n-undecane (UD), n-dodecane (DD), n-tridecane (TD),
ethyl acetate (EAc), n-butyl acetate (nBAc), isobutyl acetate (IBAc), tol-
uene (T), ethylbenzene (EB), isopropylbenzene (IPB), n-propylbenzene
with tetramethylsilane as internal standard). The proposed structure
is in full agreement with the spectroscopic data.
3.3.
The
procedure
for
5-((S)-3,7-Dimethyloctyloxy)-2-[[[4-
(
(
nPB), chlorobenzene (ClB), diethylether (DEE) tetrahydrofurane
THF), dichloromethane (DCM), chloroform (TCM), acetone (ACe)
3
(dodecyloxy)phenyl]imino]methyl]phenol (DODPIMP) (C35H55NO ;
537.82 g/mol)
were purchased from Merck AG Inc. for inverse gas chromatography
measurements.
The compound DODPIMP was prepared as reported previously
20–22]. Into a 100 mL round-bottomed flask which was connected to
[
the
hydroxybenzaldehyde (0.69 g, 2.5 mmol) and 4-(dodecyloxy)aniline
0.83 g, 3 mmol) were dissolved in 25 mL toluene. To this solution, p-
Dean-Stark
apparatus,
4-((S)-3,7-dimethyloctyloxy)-2-
3
.2. Synthesis and characterization of DODPIMP
(
The synthesis of the new salicylaldimine based chiral calamitic liquid
crystal DODPIMP is shown in Scheme 1. In the first step of the synthesis
of DODPIMP, (S)-(−)-β-Citronellol was reduced to (S)-3,7-dimethyl-1-
toluenesulfonic acid (40 mg) was added and the reaction mixture was
refluxed for 4 h at 160 °C under argon atmosphere. The end of reaction
was monitored by TLC (hexane:ethyl acetate/10:1). After cooling, the
reaction mixture was extracted into diethyl ether (3×) and the com-
2
octanol under catalytic hydrogenation conditions (H , 10% Pd/C
in MeOH). As reported previously [19], (S)-3,7-Dimethyloctyl bromide
was prepared from (S)-3,7-dimethyl-1-octanol by reaction with 48%
bined organic phases were washed with saturated solution of NaHCO
and brine, respectively. The organic solution was dried over Na SO
3
2
4
aq. HBr/conc. H
TBAHS) as catalyst. Etherification of the obtained (S)-3,7-Dimethyloctyl
bromide with 2,4-dihydroxybenzaldehyde using KHCO as base in
DMF solvent, followed by the condensation reaction with 4-
2
SO
4
using tetrabutylammonium hydrogensulfate
and then removed in vacuo. The crude product was purified by recrys-
(
tallization from acetone/methanol. Yield: 0.94 g (70%); yellow crystals.
1
3
3
H NMR (500 MHz, CDCl ) δ (ppm) = 13.88 (s; OH), 8.43 (s; HC_N),
7.26–7.23 (m, 3 arom. H), 6.85 (d, J ≈ 8.9 Hz; 2 arom. H), 6.42–6.38
H , 10% Pd/C
2
(
S)
OH
(S)
OH
MeOH
4
8% aqu. HBr / conc. H SO4
2
TBAHS
O
H
HO
(
S)
Br
+
OH
KHCO3 / DMF
O
(
S)
O
H
OH
p-TosOH / Toluene
H N
OC12H25
2
(
S)
O
N
OC12H25
OH
DODPIMP
Scheme 1. The synthesis of the new salicylaldimine compound DODPIMP.

864
H. Ocak et al. / Journal of Molecular Liquids 223 (2016) 861–867
(
2 2
m; 2 arom. H), 3.99–3.93 (m, 2H, OCH ), 3.89 (t, J ≈ 6.6 Hz; 2H, OCH ),
1
.80–1.69 (m; 3H, CH
CH ), 0.87 (d; J ≈ 6.5 Hz; 3H, CH
NMR (125 MHz, CDCl ) δ (ppm) = 163.76, 163.21, 157.99, 141.20,
13.10 (arom. C) 159.46 (HC = N), 133.11, 121.97, 115.16, 107.41,
01.58 (arom. CH), 68.35, 66.57 (OCH ), 39.24, 37.27, 36.01, 31.94,
9.68, 29.66, 29.62, 29.60, 29.42, 29.37, 29.29, 26.06, 24.66, 22.71
), 29.85, 27.98 (CH), 22.73, 22.62, 19.65, 14.15 (CH ).
2
, CH), 1.63–1.36, 1.31–1.06 (2 m; 27H, 1 CH, 13
), 0.82–0.79 (m, 9H, 3 CH
3
). APT-13
C
2
3
3
1
1
2
2
(
CH
2
3
The DODPIMP was coated on the support material (Chromosorb W
AW-DMCS-treated) with 80–100 mesh size, Merck AG Inc.) as a sta-
(
tionary phase by slow evaporation of TCM as stirring the support in LC
solution. The amount of coated DODPIMP on the support was deter-
mined as 9.42% by calcination. Silane treated glass wool used to plug
the ends of the column was obtained from Alltech Associates, Inc. A
Hewlett-Packard 6890N model gas chromatograph with a thermal con-
ductivity detector was used to measure the retention times of the sol-
vents and air. The column was made of stainless steel tubing with
3
.2 mm outside diameter and 1 m length. A trace amount of solvent
was injected into the chromatograph. The column was conditioned at
73 K for 24 h under a helium atmosphere. Transition temperatures
⁎
Fig. 1. The broken fan-shaped texture of the SmC phase obtained between crossed
3
polarizers at 68 °C on cooling; the inset shows the finger-print texture of the SmC*
phase at 61 °C.
were measured and optical investigations were carried out using a
Mettler FP-82 HT hot stage and a control unit in conjunction with a
Leica DM2700P polarizing microscope and Leica DMC2900 Digital Cam-
era. The associated enthalpies were obtained from DSC-thermograms
which were recorded on a Perkin-Elmer DSC-6, heating and cooling
When transitions such as melting, glass and nematic–isotropic tran-
sitions occur, generating an aggregation change for the stationary phase,
a break in the linear variations appears [24]. Linearity is observed when
the stationary phase remains at the same thermodynamic equilibrium
state. Thermodynamic interaction of DODPIMP in the liquid state is
meaningful at the linear thermodynamic equilibrium region. Since the
linearity occurred at the temperatures between 373.2 and 398.2 K, the
−
1
rate: 10 °C min
.
4
. Result and discussion
∞
4
.1. Liquid crystalline properties
Flory-Huggins interaction parameters, χ12 of DODPIMP were deter-
mined at this temperature range and given in Table 2.
∞
The transition temperatures, corresponding enthalpy values and
mesophase type observed for DODPIMP by polarizing microscope
PM) and differential scanning calorimetry (DSC) are given in Table 1.
The new chiral salicylaldimine compound DODPIMP exhibits
The values χ12 b 0.5 represent favorable interaction of LC with the
∞
solvent whereas the values χ12 N 0.5 indicate favorable interactions at
∞
(
infinitely lower solvent concentration. The values of χ12 in Table 2 sug-
gest that n-alkanes and aliphatic acetates are poor; however benzene
derivatives are good solvents for DODPIMP. It can be said from data in
Table 1 that toluene is the best solvent. All of the parameters decrease
with temperature indicating endothermic solubility.
enantiotropic chiral smectic C (SmC*) mesophase with finger print
and broken fan-shaped texture. The introduction of a chiral branched
unit at one of the terminals of the rod-like salicylaldimine molecule
leads to a significant chirality effect on the formation of the tilted smec-
tic phase. A comparison of the mesomorphic properties of DODPIMP
with those of related non-branched compound C/8 [23] with the same
alkyl chain length shows that transition temperatures clearly decrease
by chain branching. C/8 carrying a n-octyloxy chain instead of (S)-3,7-
dimethyloctyloxy chain only exhibits the tilted smectic phase (SmC)
as a result of the absence of a chiral moiety (see Table 1).
The parameter Ω ∞1 indicating the thermodynamic interaction of
DODPIMP with solvents were also determined from the same raw re-
tention data and given in Table 3.
The texture of SmC* mesophase on cooling and DSC-traces (second
−
1
heating and cooling, 10 °C min ) of DODPIMP are shown in Figs. 1
and 2, respectively.
nd
← 2 Cooling
Cr
SmC*
Iso
4
.2. Thermodynamic interactions of Liquid DODPIMP
0
The V
g
values of the solvents on DODPIMP were determined by
using Eq. (1). Figs. 3 and 4 show the variation of the specific retention
volumes of n-alkanes, nBAc, IBAc, EAc, nPB, IPB, EB, T and ClB with tem-
perature between 373.2 and 393.2 K, respectively.
Cr
Heating
SmC*
Iso
nd
2
→
Table 1
The phase transition temperatures of the DODPIMP.
Compound
T/°C [ΔH kJ mol−1]a
1
0
20 30 40 50 60 70 80 90 100 110 120 130 140
DODPIMP
C/8
Cr 53.2 [30.9] SmC* 93.0 [7.0] Iso
Cr 76.5 [49.0] SmC 125.6 [7.9] Iso
[23]
T / °C
a
Enthalpy values in italics in brackets; Abbreviations: Cr = crystalline, Sm C* = chiral
smectic C phase, Iso = isotropic liquid phase.
Fig. 2. DSC-traces (second heating and cooling, 10 °C min−1) of DODPIMP.

H. Ocak et al. / Journal of Molecular Liquids 223 (2016) 861–867
865
7
6
5
4
3
2
1
.00
.00
.00
.00
.00
.00
.00
Table 3
∞
The weight fraction activity coefficients, Ω
1
, of DODPIMP.
T(K) Hx Hp nBAc IBAc EAc nPB IPB EB
O
N
D
T
ClB
(
1)
3
3
73.2 7.5 7.3 6.8 6.5 6.2 5.5
78.2 7.7 7.0 6.7 6.3 6.0 5.2
5.7
5.6
5.4
5.4
5.2
5.1
7.9 4.2
7.3 4.0
6.9 3.8
6.8 3.8
6.3 3.8
6.0 3.7
3.8 4.2 3.6 3.2
3.8 4.0 3.4 3.1
3.7 3.9 3.4 3.1
3.7 3.9 3.4 3.1
3.7 3.9 3.5 3.1
3.6 3.9 3.4 3.1
(
2)
383.2 7.7 6.9 6.5 6.2 6.1 5.2
3
3
3
88.2 7.6 6.6 6.4 6.1 6.0 5.1
93.2 7.6 6.6 6.4 6.1 5.9 4.9
98.2 7.2 6.5 6.2 6.2 5.7 5.0
(
3)
(
4)
(
5)
Table 4
The selectivity coefficients of the DODPIMP for the structural isomer pairs: nBAc/IBAc and
nPB/IPB.
α=(tR(1)−t
A A
)/(tR(2)−t )
T(K)
t
R(nBAc)/tR(IBAc)
tR(nPB)/tR(IPB)
0
.00245
0.00250
0.00255
0.00260
0.00265
0.00270
0.00275
3
3
3
73.2
78.2
83.2
1.3
1.3
1.3
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
-
1
1
/T(K )
0
g
Fig. 3. The specific retention volume diagrams, V
5) on DODPIMP.
, of D (1), N (2), O (3), Hx (4) and Hp
388.2
393.2
3
(
98.2
6
5
5
4
4
3
3
2
2
.00
.50
.00
.50
.00
.50
.00
.50
.00
(
(
(
1)
2)
3)
4.3. The selectivity coefficients of liquid DODPIMP to the structural isomers
The selectivity coefficients, α of the pairs of nBAc/IBAc and nPB/IPB
were obtained using their retention times in order to reveal the usage
of DODPIMP as the isomer selective stationary phase in a gas–liquid
chromatography column. The values given in the Table 4 suggest a
good separation can be reached for the pairs of nBAc/IBAc and nPB/IPB
if longer columns are used although the separation coefficients are not
so high.
(4)
(
(
(
5)
6)
7)
(
8)
0
.00245
0.00250
0.00255
0.00260
0.00265
0.00270
0.00275
-
1
1
/T(K )
0
Fig. 4. The specific retention volume diagrams, V
g
, of nPB (1), IPB (2), ClB (3), EB (4), nBAc
(5), T (6), IBAc (7) and EAc (8) on DODPIMP.
According to Guillet, the solvent is good if Ω∞ b 5 and poor if Ω∞
N10.
1 1
The values between 5 and 10 indicate moderately good solubility. The
values in Table 3 suggest n-alkanes and aliphatic acetates are moderate-
ly good; while benzene derivatives are good solvents for DODPIMP. The
∞
values of Ω
1
suggest the best solvent is ClB for DODPIMP unlike to the
∞
suggestion of χ12. It might be expected that ClB is better solvent than
T since electron attractive chlorine atoms can make favorable interac-
∞
tions with unbounded electrons of DODPIMP. This suggests that Ω
1
values are more reliable than χ 1∞ 2 values to reveal the thermodynamical
interactions of a LC with solvents. It should be also noted the definition
∞
of Ω
1
based on the fundamental physical chemistry laws.
N
Fig. 5. The net retention volumes, V , of nonpolar solvents: D (1), N (2), O (3) and Hp (4).
Table 2
Flory-Huggins interaction parameters, χ 1∞ 2, of DODPIMP with solvents.
T(K)
Hx
Hp
O
N
D
nBAc
IBAc
EAc
nPB
IPB
EB
T
ClB
3
3
3
3
3
3
73.2
78.2
83.2
88.2
93.2
98.2
0.61
0.65
0.64
0.64
0.63
0.59
0.80
0.76
0.73
0.70
0.69
0.67
0.80
0.78
0.75
0.74
0.73
0.71
0.80
0.78
0.76
0.75
0.74
0.76
0.81
0.79
0.80
0.79
0.76
0.74
0.75
0.71
0.69
0.69
0.64
0.65
0.73
0.71
0.67
0.66
0.63
0.61
1.07
0.99
0.92
0.90
0.83
0.77
0.47
0.44
0.37
0.39
0.36
0.36
0.40
0.38
0.36
0.36
0.36
0.33
0.45
0.42
0.40
0.40
0.40
0.38
0.28
0.23
0.22
0.21
0.25
0.20
0.39
0.37
0.36
0.36
0.37
0.36

866
H. Ocak et al. / Journal of Molecular Liquids 223 (2016) 861–867
Table 5
D
S
The dispersive surface energy, γ
Dorris-Gray.
of DODPIMP determined by the methods of Schultz and
(mJ/m2)
D
S
γ
T (K)
Schultz
Dorris-Gray
3
3
3
3
03.2
08.2
13.2
18.2
39.3
34.6
33.7
29.5
40.8
36.2
35.5
31.3
S
∗
⁎
A
Fig. 8. The plot of −ΔH /AN versus DN/AN .
The dispersive component of the surface energy of DODPIMP was
determined using both Schultz and Dorris-Gray methods and given in
Table 5.
Dispersive surface energy of DODPIMP was found approximately
2
4
0 mJ/m around room temperature and decreased with temperature.
The dispersive surface energies of some LCs were reported around
2
3
5 mJ/m in the literature [25,26]. Our value is comparable with literature
data. As it can be observed from Table 5, Dorris-Gray method gives a little
bit higher values than other one although they are very close to each other.
4.5. Acidity-basicity of crystalline DODPIMP surface
N
Fig. 6. The net retention volumes, V of polar solvents: THF (1), TCM (2), DCM (3), ACe
(4) and DEE (5).
The V
N
diagrams of polar solvents were given in the Fig. 6. It can be
change linearly with the reciprocal of the abso-
seen the logarithm of V
N
lute temperature. This suggests any thermal transition does not occur at
4
.4. Dispersive surface energy of crystalline DODPIMP
this temperature range.
The specific component of adsorption free energy, −ΔG
lated using the difference between the RTlnV
S
A
, was calcu-
The adsorption properties of DODPIMP surface were investigated by
N
values of the polar sol-
IGC technique between 303.2 K and 318.2 K, which it is crystalline state.
Dispersive component of the surface energy of DODPIMP can be obtain-
vent and hypothetical n-alkane which was derived by the linear fit of
the nonpolar reference line at a given temperature, according to the
Eq. (11) at the corresponding temperature. The plot at 303.2 K was
given as an example in Fig. 7.
ed using V
cannot make specific interactions with the stationary phase. The V
values of n-alkanes on the DODPIMP were obtained using Eq. (5) and
given in Fig. 5 as the plots of LnV versus 1/T.
N
data of only nonpolar probes such as n-alkanes since they
N
The values of K
⁎
A
respectively, of the plot of −ΔH /AN versus DN/AN as shown in Fig. 8.
A D
and K were calculated from the slope and intercept,
S
∗
N
N L
Fig. 7. A plot of RTLnV vs. a(γ
)0.5 for n-alkanes and the polar solvents adsorbed on DODPIMP at 303.2 K.
D

H. Ocak et al. / Journal of Molecular Liquids 223 (2016) 861–867
867
The values of K
The ratio of K /K which is 10.6, suggests the surface of DODPIMP has
basic character in nature.
A
and K
D
are found to be 0.11 and 1.17, respectively.
Humboldt Foundation, for financial support toward liquid crystal
research.
D
A
References
5
. Conclusions
[
[
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good while n-alkanes and aliphatic acetates are poor solvents. However
∞
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1
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194–201.
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∞
is more reliable than χ 1∞ 2 in determination of the quality of a
gests Ω
1
[
[
[
solvent for a LC, at least in this study.
The selectivity coefficients of DODPIMP to the structural isomers
studied in this study were found around 1.2 at temperatures between
[
[
3
73.2 and 398.2 K, which the LC is in the liquid state. The dispersive sur-
D
−2
face energy,γ
S
of DODPIMP was found as 40 mJ m as a mean of the
data of n-alkanes. The surface of
DODPIMP was estimated as a basic character according to the value of
/K = 10.6 by means of V data of TCM, DCM, ACe, DEE and THF.
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N
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(
K
D
A
N
9
Acknowledgement
(
25] C. Yorur Goreci, F. Cakar, M. Gultekin, Cankurtaran, F. Karaman, B. Bilgin Eran,
MolCryst Liq Cryst. 587 (2013) 28–40.
26] F. Cakar, H. Ocak, E. Öztürk, S.M. Yaniç, D. Kaya, N. San, Ö. Cankurtaran, F. Karaman,
B. Bilgin Eran, Liq. Cryst. 41 (9) (2014) 1323–1331.
This research has been supported by Yildiz Technical University Sci-
entific Research Projects Coordination Department. Project Number:
2
013-01-02-KAP06. B. Bilgin-Eran is grateful to the Alexander von