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.