Star-shaped azomethines based on tris(2-aminoethyl)amine. Characterization, thermal and optical study

Article abstract of DOI:10.1016/j.saa.2009.12.030

The synthesis and detailed (physico)-chemical (¹H/¹³C NMR, FTIR, UV-vis and elemental analysis) characterizations of new star-shaped compounds based on tris(2-aminoethyl)amine, including in their structure an azomethine function (HC{double bond, long}N-) and alkoxysemiperfluorinated (-O-(CH₂)₃-(CF₂)₇-CF₃), octadecyloxy aliphatic (-O-(CH₂)₁₇-CH₃) chain or two phenyl rings (-Ph-Ph-) as a terminal group, were reported. The mesomorphic behavior was investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and additionally by FTIR(T) and UV-vis(T) spectroscopy. Wide-angle X-ray diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Moreover, the azomethine A1 was electro-spun to prepare fibers with poly(methyl methacrylate) (PMMA) and investigated by DSC and POM. Additionally, a film of the A1 with PMMA was cast from chloroform and the thermal properties of the film were compared with the thermal properties of the fiber and powder. It was showed that terminal groups dramatically influence the thermal and optical properties of the star-shaped azomethines.

Full text of DOI:10.1016/j.saa.2009.12.030

Spectrochimica Acta Part A 75 (2010) 891–900
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Star-shaped azomethines based on tris(2-aminoethyl)amine. Characterization,
thermal and optical study
Agnieszka Iwana,∗, Henryk Janeczekb, Bozena Kaczmarczykb, Bozena Jarzabekb,
Michal Sobotab, Patrice Rannouc
a Electrotechnical Institute, Division of Electrotechnology and Materials Science, M. Sklodowskiej-Curie 55/61 Street, 50-369 Wroclaw, Poland
b Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Street, 41-819 Zabrze, Poland
c Laboratoire d’Electronique Moléculaire, Organique et Hybride, UMR5819-SPrAM (CEA-CNRS-Univ. J. FOURIER-Grenoble I), INAC Institut Nanosciences & Cryogénie,
CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France
a r t i c l e i n f o
a b s t r a c t
The synthesis and detailed (physico)-chemical (1H/13C NMR, FTIR, UV–vis and elemental analysis) charac-
terizations of new star-shaped compounds based on tris(2-aminoethyl)amine, including in their structure
an azomethine function (HC N–) and alkoxysemiperfluorinated (–O–(CH2)3–(CF2)7–CF3), octadecyloxy
aliphatic (–O–(CH2)17–CH3) chain or two phenyl rings (–Ph–Ph–) as a terminal group, were reported. The
mesomorphic behavior was investigated by means of differential scanning calorimetry (DSC), polarized
optical microscopy (POM) and additionally by FTIR(T) and UV–vis(T) spectroscopy. Wide-angle X-ray
diffraction (WAXD) technique was used to probe the structural properties of the azomethines. More-
over, the azomethine A1 was electro-spun to prepare fibers with poly(methyl methacrylate) (PMMA)
and investigated by DSC and POM. Additionally, a film of the A1 with PMMA was cast from chloroform
and the thermal properties of the film were compared with the thermal properties of the fiber and pow-
der. It was showed that terminal groups dramatically influence the thermal and optical properties of the
star-shaped azomethines.
Article history:
Received 26 May 2009
Received in revised form
29 September 2009
Accepted 8 December 2009
Keywords:
Star-shaped azomethines
Imines
Liquid crystalline
FTIR
UV–vis
Mesomorphic behavior
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
analyzed hitherto. For this reason we decided to synthesized
star-shaped azomethines having as a central core one molecule
Liquid crystalline (LC) dendrons and dendrimers present an
interesting class of branched compounds. Their molecules combine
structural units capable of LC mesophase formation with branched
or dendritic architecture [1]. A lot of papers have been dedi-
cated to investigate liquid crystalline properties of poly(propylene
imine) dendrimers with different generations based on tripheny-
lene [2]. However, in all papers dendrimers have been based on
two or more triphenylene units as a central core [2]. Only in
two papers a scientist synthesized dendritic oligoamines based
on one molecule of tris(2-aminoethyl)amine [3a]. For example,
Vogtle et al. [3a] obtained dendritic oligoamines via N,N-bis-
sulfonylation with various sulfonyl chlorides. However, authors
[3a] did not investigate the mesomorphic behavior of these
compounds. Berna et al. [3b] synthesized novel monodisperse
PEG-dendrons as new tools for targeted drug delivery. To the
best of our knowledge LC properties of star-shaped azomethines
based on one molecule of tris(2-aminoethyl)amine were first time
of tris(2-aminoethyl)amine and different terminal groups such
as alkoxysemiperfluorinated (–O–(CH2)3–(CF2)7–CF3) or octade-
cyloxy aliphatic (–O–(CH2)17–CH3) chain or two phenyl rings
(–Ph–Ph–). A special attention in our work was paid to investigate
star-shaped azomethine with the alkoxysemiperfluorinated chain,
because of the combination of polar and steric effects and the great
strength of the C–F bond [4].
In this paper we report on investigation of the thermal behavior
of star-shaped azomethines on the basis of DSC, POM techniques
and vibrational spectral data. The effect of the kind of end groups
(aliphatic or aromatic) on the liquid crystalline phase transitional
behavior in a series of star-shaped azomethines has also been
studied. We paid particular attention to the mesomorphism of
the star-shaped azomethines by using FTIR(T) and UV–vis(T) tech-
niques. The structural characterization was performed by NMR and
FTIR characteristic completed via X-ray diffraction measurements
and optical investigations. In this paper thermal properties of the
star-shaped azomethine A1 were preliminarily studied via electro-
spinning technique. To the best of our knowledge the absorption
properties of the star-shaped azomethines in the function of tem-
perature were first time analyzed hitherto.
∗
Corresponding author. Tel.: +48 713283061.
E-mail address: a.iwan@iel.wroc.pl (A. Iwan).
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.12.030

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A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
Fig. 1. Synthetic route and chemical structure of the star-shaped azomethines.
2. Experimental
centers, heights and widths of particular peaks, were obtained by
analysing the second derivative spectra. An interactive procedure
and Gaussian–Lorentzial fitting of curves were chosen to correct
these parameters.
2.1. General
All chemicals and solvents were of reagent grade obtained
from Aldrich Chemical Co., and all solvents were dried by stan-
dard techniques. The synthesized compound was characterized by
1H and 13C NMR and elemental analysis. The compound was also
characterized by Fourier transform infrared (FTIR) and ultraviolet-
visible (UV–vis) absorption spectroscopy. NMR was recorded on a
Varian Inova 300 MHz Spectrometer. Chloroform-d (CDCl3) con-
taining TMS as an internal standard was used as solvent. Elemental
analyses (C, H, and N) were carried out by the 240C Perkin-
Elmer analyzer. Infrared spectra were acquired on a DIGILAB
FTS-40A Fourier transform infrared spectrometer in the range of
4000–400 cm−1 at a resolution of 2 cm−1 and for an accumulated
32 scans. Samples were analyzed in a form of films obtained after
evaporating chloroform from solutions onto potassium bromide
windows UV–vis absorption spectra were recorded on Hewlett-
Packard 8452A spectrophotometer. X-ray diffraction patterns were
recorded using powder samples on a wide-angle HZG-4 diffrac-
tometer working in typical Bragg geometry. CuK␣ radiation was
applied.
The phase transitions and mesogenicity were studied by dif-
ferential scanning calorimetry (DSC) and polarizing microscope
observations (POM). The textures of the liquid crystalline phases
were observed with a Polarized Optical Microscopy (POM). DSC
was measured on a TA-DSC 2010 apparatus using sealed aluminium
pans under nitrogen atmosphere at a heating/cooling scan in a tem-
perature range from 25 ◦C to over the clearing point.
FTIR spectra recorded at elevated temperatures were obtained
using Carl Zeiss Jena high-temperature control equipment in the
temperature range from 20 to 145 ◦C. The sample was heated under
nitrogen at the rate of 2 ◦C/min and FTIR spectra were recorded by
10 ◦C. The same conditions were applied during cooling to 20 ◦C.
In order to determine the quantitative relations among the bands
detected in the region of 1280–1100 cm−1, a WIN-IR curve fitting
program was used. The initial parameters, i.e. number of peaks,
The temperature dependence of the UV–vis spectra was mea-
sured for thin film on the quartz (film cast from chloroform)
by JASCO V-570 UV-Vis-NIR spectrometer using a temperature-
controlled optical cell in a temperature range from the room
temperature to clearing point in the heating process.
Electro-spinning apparatus, composed of a high voltage power
supply (18 kV), a syringe pump (Prefusor Type 871102) with a
glass syringe and stainless-steel blunt-ended needle (inner diam-
eter: 0.5 mm) and a grounded electron microscope mounts as a
counter electrode or a grounded flat metal collector was used. Nee-
dle and collector were mutually perpendicular, the needle being
placed vertically. The solution of azomethine A1 and poly(methyl
methacrylate) (PMMA) (A1/PMMA) was electro-spun using the fol-
lowing conditions: applied voltage of 18 kV, needle to collector
distance = 18 cm with flow rate = 5.4 × 10−2 mL/min.
2.2. General synthetic procedure
Aldehyde (3.5 mmol) was dissolved in 1-methyl-2-pyrro-
lidinone (NMP) (10 ml). To this solution was added a solution of
tris(2-aminoethyl)amine (TEA) (1.00 mmol, 0146 g) in NMP (10 ml).
The reaction mixture was stirred at room temperature for 5 days.
Then the compound was washed with ethanol and later with ace-
tone and dried at 50 ◦C under vacuum for 6 h.
A1 (N–[–CH2–N CH–C6H4–O–(CH2)3–(CF2)7–CF3]3): yellow
powder, 1H NMR (300 MHz, CDCl3, TMS) [ppm]: ı 8.04 (s, 3H,
CH N–); 7.47 (m, 6H, HAr–CH N–); 6.86 (m, 6H, HAr); 3.65–4.06
(m, 6H, CH2–O); 2.90 (m, 6H, –N–CH2–); 2.27–2.35 (m, 6H,
CH2–CH2–CH2–CF2); 2.09–2.17 (m, 6H, –N–CH2–CH2). 13C NMR
(75 MHz, CDCl3, TMS) [ppm]: ı 161.10, 160.90, 160.38 (–CH N–),
129.59, 118.41, 114.44, 114.22, 110.73, 66.33, 60.05, 59.87, 55.79,
55.30, 28.17, 27.90, 27.62, 20.56. FTIR: ꢀmax in cm−1: 3063 and
3037 (␯CH), 2944 and 2920 (␯aCH2), 2875 and 2840 (␯sCH2), 1643
(␯C N), 1607, 1579, 1512, 1451 and 1422 (␯Ph), 1478 (␦CH2), 1372

A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
893
Table 1
Anal. Calcd. for C42H36N4 (596.762): C, 84.53%; H, 6.08%; N, 9.39%.
Found: C, 84.45%; H, 6.26%; N, 9.69%. UV–vis in dichloroethane ꢁmax
at 282 nm. UV–vis in NMP ꢁmax at 284 nm.
Identified mesophases and thermal parameters of the azomethines determined by
POM.
Phase transition behavior, cooling, detected by POM [◦C]
A1
2.3. Fiber and blend preparation
I 140, Sm A 139 till 78, Cr or frozen Sm A < 77.5
A2
Cr 68
A3
Blend solution of A1/PMMA (1/99 w/w); in 10 w/w of chloro-
form was prepared. Farther, this blend solution in two ways was
processed, as a casted film (about 1 mm thickness, dried 2 weeks in
vacuum dryer at 100 ◦C) and electro-spun fibers (fibers were dried
2 weeks in vacuum dryer at 100 ◦C).
I 115, SmX 104 till 100, Cr < 100
I, isotropic; Cr, crystalline; Sm, smectic
(␻CH2), 1303 (␦CH), 1237 (␯CF2 and ␯Ph–O), 1204 (␯CF2), 1149
(␯CF3), 1056 and 1026 (␦CH/␯CO), 975 and 831 (␥CH), 810 (␳CH2),
744 and 706 (␥Ph), 731 (␥CH2) 722 (␥CH), 659 (␦C–C–F). Mp. (heat-
ing rate 10◦/min): 86 ◦C. Tg (DSC, 4◦/min): 5.5 ◦C. Anal. Calcd. for
C57H39F51N4O3 (1796.863): C, 38.10%; H, 2.19%; N, 3.12%. Found:
C, 38.45%; H, 2.46%; N, 2.99%. UV–vis in chloroform ꢁmax at 267 nm.
UV–vis in NMP ꢁmax at 268 nm.
3. Results and discussion
3.1. Synthesis and characterization
Three star-shaped azomethines described in this paper were
prepared from three different aldehydes and tris(2-aminoeth-
yl)amine solution condensation in 1-methyl-2-pyrrolidinone
(NMP) at room temperature. Synthetic route along with the
chemical structures of the star-shaped azomethines (abbreviated
hereinafter as A1, A2 and A3) are presented in Fig. 1, whereas details
of their synthesis procedure are given in Section 2.
Their expected chemical constitution was clearly confirmed
by spectroscopic studies. In particular the signals in the range of
160–161 ppm, present in the spectra of all compounds, confirm the
existence of the imine group carbon atoms. In the case of the imine
structure two isomers are possible (cis and trans), even though the
trans structure is always supposed to be thermodynamically more
stable. A splitting of the signals in 13C NMR spectra of the A1 and
A2 seems to confirm the coexistence of the isomers. While in the
carbon NMR spectrum of the A3 one signal at 161.55 nm was found,
which confirmed that in this case the imine band exists only in trans
conformation.
A2 (N–[–CH2–N CH–C6H4–O–(CH2)17–CH3]3): pale yellow
powder, 1H NMR (300 MHz, CDCl3, TMS) [ppm]: ı 8.04 (s, 3H,
CH N–); 7.47 (d, 6H, HAr–CH N–); 6.85 (d, 6H, HAr); 3.97 (m, 6H,
CH2–O–); 3.64 (m, 6H, –N–CH2–); 2.90 (m, 6H, –N–CH2–CH2); 1.79
(m, 6H, –CH2–CH2–O–); 1.59 (m, 6H, –CH2–CH2–CH2–O–); 1.26 (m,
42H, –(CH2)14); 0.86–0.90 (m, 6H, CH3). 13C NMR (75 MHz, CDCl3,
TMS) [ppm]: ı 161.24, 161.05 (–CH N–), 131.97, 129.54, 129.04,
114.46, 114.39, 68.08, 60.03, 55.83, 31.91, 29.69, 29.61, 29.41, 29.35,
29.22, 29.03, 26.04, 22.68, 14.11. FTIR: ꢀmax in cm−1: 3071 and
3037 (␯CH), 2955 and 2917 (␯aCH2), 2850 (␯sCH2), 1643 (␯C N),
1608, 1577, 1513, 1463 and 1422 (␯Ph), 1473 (␦CH2), 1372 (␻CH2),
1303 and 1286 (␦CH), 1253(␶CH2 and ␯Ph–O), 1167 (␯Ph–O), 1056
and 1026 (␦CH/␯CO), 965 and 837 (␥CH), 810 (␳CH2), 729 and 720
(␳CH2), 706 and 650 (␥Ph). Mp. (heating rate 10◦/min): 79 ◦C. Tg
(DSC, 2◦/min): 10.6 ◦C. Anal. Calcd. for C78H132N4O3 (1173.908): C,
79.80%; H, 11.33%; N, 4.77%. Found: C, 79.34%; H, 11.50%; N, 4.54%.
UV–vis in dichloroethane ꢁmax at 266 nm. UV–vis in NMP ꢁmax at
281 nm.
The 1H NMR spectra, detected in CDCl3 solution also confirmed
the azomethine structures and the signals corresponding to the
proper protons are presented in Section 2. In particular the sig-
nals in the range of 8.04–8.13 ppm present in the spectra of all
azomethines confirmed the presence of the imine group. A signif-
icant down-field shift of the imine group proton was observed in
the azomethine A3, synthesized from 4-biphenylcarboxaldehyde.
The presence of imine groups was also confirmed by FTIR spec-
A3 (N–[–CH2–N CH–C6H4–C6H5]3): yellow powder, 1H NMR
(300 MHz, CDCl3, TMS) [ppm]: ı 8.13 (s, 3H, CH N–); 7.40–7.59
(m, HAr); 3.73 (m, 6H, –N–CH2–); 2.96 (m, 6H, –N–CH2–CH2). 13
C
NMR (75 MHz, CDCl3, TMS) [ppm]: ı 161.55 (–CH N–), 143.04,
140.31, 135.14, 130.25, 128.99, 128.82, 128.48, 128.39, 127.66,
127.34, 127.25, 127.17, 127.04, 60.11, 59.95, 55.58, 55.10. FTIR:
ꢀmax in cm−1: 3055 and 3032 (␯CH) and 2936 and 2895 (␯aCH2),
2876, 2837 (␯sCH2), 1644 (␯C N), 1605, 1582, 1562, 1450 and
1408 (␯Ph), 1487 (␦CH2), 1372 (␻CH2), 1311 and 1287 (ıCH), 1227
(␶CH2), 1179 (␯C–N ), 1157 (␯C–N–), 1115, 1076, 1039, 1024 and
1007 (␦CH), 984, 947, 929 and 837 (␥CH), 762 (␦Ph), 722 (␥Ph).
Mp. (heating rate 10 deg./min): 98 ◦C. Tg (DSC, 5◦/min): 19.5 ◦C.
troscopy since in each case the band characteristic of the HC
N
stretching deformations is detected. The exact position of this band
varies in the spectral range of 1643–1644 cm−1 (see Section 2). In
addition to the HC N stretching band, a band at about 1606 cm−1
can be distinguished ascribed to the C C stretching deformations
in the aromatic ring.
Table 2
Transition temperatures and enthalpies of the azomethines detected by DSC.
Phase sequences
Code
Phase transitions [◦C] (corresponding enthalpy changes) [J/g]
Heating
Cooling
A1a
A1b
A1c
A2d
A3e
A3f
60.5 (0.65), 79.3 (10.3), 132.9 (1.59)
60.3 (0.3), 78.7 (9.6), 132.2, 134.0 (1.3)
59.9 (0.9), 77.8 (8.3), 132.4, 133.4 (1.14)
63.5 (21.3), 77.3 (138.1)
101.6 (29.9)
101.9 (13.1), 109.5 (6.3)
131.9 (1.30), 117.6 (0.2), 76.4 (9.7), 56.3 (0.05), 43.9 (0.57)
132.6, 131.2 (1.16), 75.8 (9.9), 55.7 (0.4), 43.1 (0.9)
132.8, 131.9 (1.1), 75.2 (9.4), 56.2 (0.5), 45.5 (0.3)
60.8 (115.6)
85.0, 78.7 (36.1)
93.6 (14.3), 77.7 (12.5)
a
Cooling 1◦/min, heating 1◦/min.
b
c
d
e
f
Cooling 0.5◦/min, heating 0.5◦/min.
Cooling 0.25◦/min, heating 0.25◦/min.
Cooling 0.25◦/min, heating 0.25◦/min.
Cooling 0.3◦/min, heating 0.5◦/min.
Heating 0.5◦/min, cooling 0.2◦/min.

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A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
The DSC curves recorded with repeated heating–cooling cycles
allowed the evaluation of Tg values of the synthesized azomethines
in the range of 5.5–19.5 ◦C (see Section 2). It is obvious that they
depend on the structure of the compounds. First, we notice that
A3 shows significantly higher Tg, consistent with their more rigid
chains. The lowest Tg for the compound A1 was found.
3.2. Mesomorphic behaviors
The compounds were studied by differential scanning calorime-
try (DSC) and polarized optical microscopy (POM) methods to
determine their mesomorphic properties. First, one may accept that
upon the DSC and POM analyses the compounds A1 and A3 exhib-
ited mesomorphic transition behaviors, while A2 did not show
mesomorphic behaviors. The phase sequences, transition tempera-
tures and enthalpies of the star-shaped azomethines are presented
in Tables 1 and 2. The tentative mesophase identifications and the
sequences of phase transitions related to all the compounds are
based on the identification of textures appearing in two reference
textbooks for liquid crystals [5–6] and on repeated POM and DSC
experiments.
In the POM study, the compound A1 exhibited stable enan-
tiotropic smectic A (SmA) liquid crystal phase. Full isotropisation
of the A1 at 140 ◦C was observed and was existed over a very small
temperature range of ca. 0.5 ◦C. The photomicrographs of the opti-
cal textures of mesophase obtained for A1 at 110 ◦C are presented
in Fig. 2a and b.
A1 has three semiperfluorinated alkoxy arms and it is rather
apolar LC molecule. Therefore it was not surprising that in between
two (polar) glass plates, only SmA planar focal-conic texture of
A1 was found and was almost immediately transformed into
homeotropically aligned SmA domains. Moreover, also “so-called”
oily streaks texture, which is rather a typical texture of the SmA
mesophase was observed (Fig. 2b). During a cooling scan of A1 from
the isotropisation state, we have not seen a clear transition of SmA
mesophase to Cr. Below Tc just a frozen homeotropically aligned
SmA mesophase of A1 was observed.
The homeotropic texture was observed by using clean glass slide
and coverslip (sample sandwiched in between two glass plates). It is
known that, in the homeotropic texture, the molecules are aligned
with an average perpendicular orientation with respect to the lay-
ers that lie parallel to the surfaces. Additionally, the presence of
three nitrogen atoms in the azomethine structure, which are able
to interact with glass substrate and as a result induce the molecules
to readily self-assemble to be perpendicular to the glass substrate
and then to form homeotropic alignment cannot to be excluded.
On the other hand A2 did not show mesomorphic behavior
and exhibited only Tc (68.0 ◦C) and Tm (79 ◦C) during cooling and
heating of the sample A2. A2 crystallized in the form of beautiful
spherulites (Fig. 2c). This conclusion was confirmed by performing
DSC (see in the next part of the paper).
Fig. 2. Polarizing microscope photographs of the A1 at 110 ◦C (a), of the A1 at 90 ◦
C
(b) and of the A2 at 60 ◦C (c).
The compound A1 was investigated by DSC during different
heating and cooling cycles, i.e. 1◦/min, 0.5◦/min and 0.25◦/min (see
Table 2 and Fig. 3b). Also the compound A3 was investigated by
DSC during different heating and cooling cycles (see Table 2). DSC
thermographs of the A3 during cooling at 0.3◦/min showed double
peaks with maxima at 85.0 ◦C and 78.7 ◦C, and small exotherm at
55.6 ◦C. During heating of the A3 at 0.5◦/min broad peak at 101.6 ◦C
was found. DSC results of the A3 during heating of the sample at
0.5 deg/min showed two peaks at 102.0 and 109.5 ◦C, while during
cooling of the A3 at 0.2◦/min two broad exotherms with maxima at
93.6 and 77.7 ◦C were observed (Table 2).
For the investigated azomethines different mesomorphic prop-
erties were observed. This behavior indicates the role of the
terminal groups in creating their mesomorphic properties.
This is worth to notice as well that in accordance with the
results of DSC measurements the melting temperatures dis-
A3 is a LC compound with smectic mesophase and temperature
of isotropisation at 115 ◦C. The investigations by POM showed that
the compound A3 during a heating scan exhibited the Sm phase
from 100.0 to 104.1 ◦C. During a cooling scan the similar scenario
was found.
3.3. Thermal behaviors detected via DSC
During heating of the azomethine A2 at 0.25 ◦C/min one
exotherm at 63.5 ◦C indicating ordering of crystalline phase along
with endotherm at 77.3 ◦C was observed (Fig. 3a). During cooling
of the A2 at 0.25 ◦C/min one exotherm at 60.8 ◦C and small peak at
31.5 ◦C (crystallization) was observed. DSC thermograms of the A2
are presented in Fig. 3a.

A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
895
Fig. 4. X-ray profiles of the azomethines A1–A3 at room temperature.
pound. Moreover, two broad halo at 13.23◦ and 40.17◦ in the X-ray
profile of A2 was observed (Fig. 4). The X-ray diffraction pattern
obtained for A3 is presented in Fig. 4 and is very similar to X-ray
diffraction pattern obtained for A2. A broad two halo and sharp
reflections at wide angles are shown in Fig. 4. One broad diffraction
peak of diffusion type centered at 13.47◦ (2ꢂ) and second at 41.02◦
(2ꢂ) and three sharp reflections at 5.61◦, 19.22◦ and 23.62◦ were
observed for A3.
3.5. FTIR and FTIR(T) studies
Fig. 3. DSC traces of the (a) A2 at a heating and cooling rate of 0.25◦/min and (b) A1
To study the changes in the structure of star-shaped azome-
thines by FTIR spectroscopy the A1 was chosen as an example. First
we investigated FTIR of the A1 at room temperature. At the spec-
trum of the A1 the strongest bands appeared as a doublet at 1238
and 1204 cm−1, which correspond to the stretching vibrations of
C–F2 group [7]. The band that arises from these vibrations of C–F3
group was detected at 1149 cm−1. However at the similar frequen-
cies the band ascribed to stretching vibrations of aromatic ether
C–O group and in plane deformations of C–H group in aromatic
ring was also observed. In the aim to separate particular bands in
that region curve fitting calculations were made. Results are shown
in Table 3.
at a heating and cooling rate of 0.5◦/min.
tinctly increased in the following order: 77.3 ◦C (A2) < 79.3 ◦C
(A1) < 101.6 ◦C (A3).
The phase transitions were additionally, analyzed based on
their enthalpy values. The melting process exhibited the highest
enthalpy values and decreased from 138.1 J/mol K for A2 to the
minimal value 10.3 J/mol for A1. The parameters of the heating and
cooling process of the A1 are similar.
3.4. X-ray studies
The band at 1026 cm−1 associates with aliphatic ether group
stretching vibrations. The band corresponding to the stretching
vibrations of HC N group was detected at 1643 cm−1, i.e. at rel-
atively higher frequency in relation to previously investigated
polyazomethines and their model compounds [8]. The bands char-
acteristic for stretching vibrations of CH2 groups appeared at 2944,
2921 (asymmetric) and at 2875 and 2840 cm−1 (symmetric). Due to
their little contents in the A1 intensity these bands were relatively
small. The bands corresponding to the deformation vibrations of
this group were recorded at 1478 (in plane), 1372 (wagging) and
810 cm−1 (rocking). Hardly observable intensities were recorded
for the bands ascribed to the stretching vibrations of C–H groups
in aromatic ring, which were present at 3067 and 3034 cm−1. The
bandsattributed tothe stretching vibrations ofthephenyl ring were
detected at 1607, 1578, 1513, 1451 and 1332 cm−1, while these
of deformation vibrations of C–H groups in aromatic ring at 1115
(shoulder, in plane), 975, 865 and 831 cm−1 (out of plane) were
found. At 744 and 706 cm−1 appeared the bands associated with the
out plane deformations of the phenyl ring and at 731 and 722 cm−1
due to these of C–H2 and C–H groups, respectively. The band at
659 cm−1 interprets as arising from the deformations in plane of
C–C–F group [9].
X-ray diffraction studies of the star-shaped azomethines A1–A3
powders revealed their semi-crystalline nature. The X-ray patterns
of the A1–A3 showed very sharp diffraction peaks with several
weak diffractions in smaller angles (2ꢂ scanning), indicating that
a highly ordered crystalline structure exists in those azomethines.
The wide-angle X-ray diffraction patterns of the A1–A3 over the 2ꢂ
range of 5–60◦ are shown in Fig. 4.
The star-shaped azomethines A2–A3 exhibited two main reflec-
tions at 2ꢂ = 19.46◦ and 23.50◦, respectively (d spacing 4.56 and
3.78 Å, respectively). In the X-ray diffraction pattern of the A1 only
one main reflection at 2ꢂ was found at 19.46◦ (Fig. 4). The diffrac-
tions arising from the crystallites were observed for A1 at 6.67◦,
20.30◦, 23.01◦ and 28.38◦ (d spacing 13.27, 4.37, 3.86 and 3.14 Å,
respectively) and demonstrated less sharp diffraction peaks in the
range of 5–60◦ in comparison with the A2 and A3 (Fig. 4). Addition-
ally, broad halo at 13.74◦ in the X-ray profile of A1 was observed
(Fig. 4). In X-ray diffraction measurements of the A2, a lot of sharp
diffraction peaks were observed at wide angles at 5.66◦, 9.52◦,
21.31◦, 25.52◦ and 28.90◦ (d spacing 15.56, 9.28, 4.17, 3.48 and 3.09,
respectively) which indicates semi-crystalline nature of this com-

896
A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
Table 3
Results of the A1 curve fitting calculations in the region of 1280–1100 cm−1
.
Temp. [◦C]
␯Ph–O
␯aCF2
␯sCF2
␯C–N
␦CH
␯aCF3
␯sCF3
␯C–N–
␦CH
cm−1
Area cm−1
Area
cm−1
Area
cm−1
Area
cm−1
Area cm−1
Area cm−1
Area cm−1
Area cm−1
Area cm−1
Area
Heating
20
40
60
70
80
90
100
110
120
130
140
145
1260
1260
1259
1259
1259
1258
1258
1258
1257
1257
1257
1257
1.84 1248
1.81 1248
1.87 1247
1.83 1246
1.78 1246
1.48 1245
1.07 1244
0.90 1244
0.78 1243
0.70 1243
0.63 1243
0.57 1242
9.98 1222
9.80 1222
10.12 1221
10.32 1220
11.08 1218
14.92 1212
16.41 1208
16.76 1207
17.30 1207
17.53 1207
17.78 1207
17.91 1207
18.77 1202
19.73 1202
19.39 1201
20.65 1201
21.51 1201
22.78 1201
22.78 1201
22.13 1201
21.90 1200
20.85 1200
19.68 1200
19.15 1199
21.64 1176
19.82 1177
18.35 1176
16.24 1176
14.49 1176
8.36 1176
2.31 1175
1.92 1175
0.85 1175
0.80 1175
0.69 1176
0.77 1177
7.69 1166
7.76 1166
7.71 1166
7.89 1165
7.58 1165
6.89 1165
6.01 1164
5.96 1164
5.59 1164
6.02 1164
5.90 1164
5.79 1164
1.00 1151
1.12 1151
1.32 1151
1.44 1151
1.66 1151
2.41 1151
2.20 1152
2.24 1152
2.71 1151
2.53 1151
3.39 1151
3.61 1151
8.20 1146
8.04 1146
8.16 1145
8.23 1145
8.33 1145
7.07 1144
5.00 1144
4.65 1144
4.25 1144
4.12 1144
3.81 1144
3.69 1144
3.53 1135
3.20 1135
2.73 1135
2.52 1135
2.02 1135
1.81 1135
1.86 1135
1.80 1135
1.78 1135
1.55 1135
1.42 1135
1.36 1135
4.81 1115
4.86 1115
4.93 1115
5.00 1115
5.02 1115
4.98 1115
4.48 1114
4.47 1114
4.44 1114
4.43 1113
4.30 1113
4.31 1113
3.15
3.24
3.39
3.46
3.54
3.62
3.63
3.64
3.68
3.66
3.58
3.55
Cooling
140
130
120
110
100
90
80
70
60
40
1257
1257
1257
1257
1258
1258
1258
1259
1259
1259
1259
0.55 1242
0.59 1242
0.66 1243
0.51 1243
0.80 1243
0.93 1244
1.06 1244
1.22 1245
1.49 1246
1.61 1247
1.62 1247
18.09 1207
18.06 1207
18.06 1207
17.83 1206
17.80 1207
17.35 1207
16.84 1208
14.09 1210
10.69 1213
9.87 1220
9.52 1220
18.63 1199
19.57 1200
20.74 1200
22.72 1200
22.99 1200
24.43 1201
25.06 1201
26.85 1201
27.62 1201
20.65 1201
18.48 1202
0.92 1177
0.76 1177
0.81 1177
0.80 1176
1.23 1176
1.71 1176
2.65 1176
6.15 1176
9.78 1176
17.04 1176
20.02 1176
5.85 1164
5.77 1164
5.29 1164
5.10 1164
5.38 1164
5.12 1164
5.11 1164
4.25 1165
4.03 1165
6.63 1166
6.77 1166
4.29 1151
4.09 1151
4.17 1151
3.33 1151
3.32 1152
3.13 1152
2.98 1152
2.81 1151
2.58 1151
1.44 1151
1.36 1152
3.46 1144
3.77 1144
4.01 1144
4.49 1144
4.60 1144
5.30 1144
5.78 1144
7.31 1144
8.13 1145
8.04 1145
8.27 1146
1.48 1135
1.38 1135
1.56 1135
1.69 1135
1.93 1135
1.87 1135
1.91 1135
1.67 1135
1.67 1135
2.17 1135
2.25 1135
4.27 1113
4.37 1113
4.45 1113
4.60 1114
4.65 1114
4.71 1115
4.79 1115
4.92 1115
4.89 1115
4.86 1115
4.85 1115
3.57
3.67
3.83
4.00
4.04
4.71
4.14
4.06
3.97
3.74
3.63
20
␯a, asymmetric stretching vibrations; ␯s, symmetric stretching vibrations; ␦, in plane deformations; ␥, out of plane deformations; ␻, wagging vibrations; ␳, rocking vibrations;
Ph, phenyl.
The thermotropic phase behavior of the azomethine A1 was
additionally investigated at different temperatures by using
temperature-dependent Fourier transform infrared spectra during
heating and cooling. Changes in absorbance related to the reori-
entation of the molecules at the phase transitions were observed.
While heating A1 to 145 ◦C the greatest changes were detected
between 90 and 100 ◦C, mainly in the region corresponding to the
stretching vibrations of C–F2 and C–F3 (Fig. 5B).
As seen from curve fitting calculations (Fig. 6) the strongest
decrease in area was observed in the case of the band ascribed
to the CF2 symmetric stretching vibrations (1202 cm−1). Areas of
relatively weak bands corresponding to the CF3 group stretching
vibrations (1151 and 1146 cm−1) also diminish, for asymmetric
ones changes were progressing quickly between 80 and 100 ◦C,
while for symmetric ones continuous area decrease in the whole
temperature range takes place. On the contrary, increase of the
band associated with stretching vibrations of Ph–O group was mea-
sured, however, also in that case the most discernible changes were
observed during heating from 90 to 100 ◦C. Area of the band appear-
ing at 1222 cm−1, which was interpreted as asymmetric stretching
vibrations of CF2 group, increases from 60 ◦C, reach maximum at
100 ◦C and after this temperature diminishes to the same value as
it was at 60 ◦C. Relatively slight changes were detected for the bands
characteristic for CH2 group vibrations.
Some very small increases in intensities were observed in the
region ascribed to the stretching mode, mainly between 90 and
100 ◦C (Fig. 5A). From 80 to 130 ◦C increased the band attributed
to the out plane deformations of C–H2 and C–H groups (731,
722 cm−1), mostly between 90 and 100 ◦C (Fig. 5D). Similar changes
were detected also for the phenyl ring out plane deformations (744,
706 cm−1).
The band corresponding to the stretching vibrations of the
phenyl ring at 1607 cm−1 (Fig. 5B) diminishes its intensity during
heating from 20 to 60 ◦C and shifts to 1605 cm−1, while for that at
1513 cm−1 decrease between 80 and 90 ◦C and shift to 1510 cm−1
was observed.
The bands arising from deformation vibrations of C–H groups
in aromatic ring at 865 cm−1 increase intensities and shift to
868 cm−1, respectively, while intensity of the band at 831 cm−1
decreases (Fig. 5D). Changes were observed first of all between 90
and 100 ◦C.
Intensity of the band due to aliphatic ether group stretching
vibrations at 1026 cm−1 increased during heating (Fig. 5D). The
major differences were detected between 90 and 100 ◦C. For the
bands attributed to the stretching vibrations of HC N groups no
changes were observed (Fig. 5B).
In summary, it was demonstrated that during heating of the
A1 changes at the FTIR spectrum were rather small and were
observed mainly between 90 and 100 ◦C, which probably corre-
spond to the transition Cr–SmA. However, the biggest differences
were detected in the case of the bands corresponding to C–F2
and C–F3 group vibrations, although some changes were observed
also for the bands attributed to CH2 group and phenyl ring
vibrations.
During cooling changes in the opposite direction as it was for
heating were found. Spectra recorded at 140, 145 and at 140 ◦C
after cooling were the same, which correspond to the isotropisation
of the A1. From 130 ◦C spectra recorded at the same temperature
during heating and cooling were different. The highest differences
during cooling were observed also for the bands characteristic for
C–F2 and C–F3 group vibrations, however in that case the biggest
changes were observed between 80 and 60 ◦C for symmetric and
asymmetric stretching vibrations of CF3 and for stretching vibra-
tions of Ph–O and between 80 and 50 ◦C for symmetric ones of CF2
groups (Fig. 7). Theseobservations correspond to transition SmA–Cr
during cooling of the A1 from their isotropisation state (Table 3). As
example, C–F2 vibrations of the azomethine A1 during cooling shift
at 70 ◦C from 1207 to 1210 cm−1 which corresponds to the Iso–SmA
phase transition. When decreasing temperature from 70 to 20 ◦C,
the C–F2 vibrations of the compound A1 changes the position from
1210 to 1220 cm−1 (SmA–Cr). These observations are in quite good
agreement with DSC and POM experiments.

A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
897
Fig. 6. Changes at area bands during heating of the A1.
Thus, the changes take place at a lower temperature than for
heating. Area of band due to asymmetric stretching of CF2 increased
during cooling to 50 ◦C and strongly diminished between 50 and
40 ◦C. Areas of bands due to stretching vibrations of Ph–O, CF2 and
symmetric CF3 at 20 ◦C were slightly smaller than at the begin-
ning, before heating, while for symmetric ones of CF3 was greater.
Minor area after cooling was observed also for the bands ascribed
for stretching vibrations of C–N groups in opposite to the band
attributed to in plane deformations of C–H, for which diminishing
in area was detected.
3.6. UV–vis and UV–vis(T) studies
Electronic spectra of the star-shaped azomethines were
detected in dichloroethane and in NMP solution. The UV–vis
absorption spectra of the three compounds in solutions are char-
acterized by one well-defined absorption band in the range of
266–284 nm. The UV–vis spectra of the compounds also provided
additional evidence confirming their molecular structures. In the
following discussion, the effect of structural modifications will
be explored in terms of the effect of backbone variation. For
example, the introduction of a two directly connected phenylene
rings as terminal groups in A3 in comparison with A1 results in
about 16 nm bathochromic shift of the ꢁmax band in NMP solution
from 268 to 284 nm (4.63–4.37 eV). On the other hand replace-
ment of octadecyloxy aliphatic chain (–O–(CH2)17–CH3) in A2 by
the alkoxysemiperfluorinated chain (–(CH2)3–(CF2)7–CF3) in A1
shifts hypsochromically the ꢁmax in NMP solution from 281 to
268 nm (4.41–4.63 eV). The observed changes of the optical absorp-
Fig. 5. FTIR spectra of the A1 recorded at 20, 90, 100 and 145 ◦C in the range of
3500–2700 cm−1 (A), 1650–1300 cm−1 (B), 1300–1100 cm−1 (C) and 1100–700 cm−1
(D).
Fig. 7. Changes at area bands during cooling of the A1.

898
A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
Fig. 9. DSC traces of the A1 (a), A1/PMMA, fibers (b) and A1/PMMA, blend (c) at a
heating rate of 10◦/min.
that the differential transitions proceeds stepwise. An isosbestic
point appears when a compound is quantitatively transformed
from crystal to mesophase during heating. The absorption data of
the A1 in different temperatures are presented in Table 4.
The first and second absorption bands of the A1 were not well
defined and exhibited low intensity (Fig. 8a). To find the positions
of this band the second derivatives method was used (i.e. minimum
of the second derivative of absorption corresponds to the absorp-
tion maximum). In UV–vis spectra of the A1 the hipochromic effect
along with increase in the temperature was observed (Fig. 8a). The
first absorption band was observed around 225 nm at 25 ◦C and
was about 5 nm bathochromically shifted along with increase in
the temperature to 145 ◦C. At 25 ◦C the second absorption band at
273 nm was observed and was red shifted to 279.5 nm at 100 ◦C.
Next along with the increase in the temperature small red shift
of the second absorption band was observed (Table 4). In the
UV–vis spectra of the A1 during heating two isosbestic points were
observed (Fig. 8a). First at 237 nm due to the increase in the tem-
perature from 50 to 80 ◦C and second at 305 nm appears also in the
temperature range 50 ◦C–80 ◦C and was about 68 nm red shift in
comparison with the first isosbestic point.
The absorption spectra of the A1 gradually changed as is showed
in Table 4 and in Fig. 8a. At 80 ◦C the absorption band corresponding
to the azomethine bond at 276 nm was broader and not well defined
and was 7 nm bathochromically shifted along with increase in the
temperature to 135 ◦C which correspond to the transition Cr (or
frozen SmA) to SmA. Along with increase in the temperature from
135 to 145 ◦C the absorption bands at 230 and 282 nm decreased
the absorption intensity which correspond to the transition SmA-
isotropisation. These observations are in agreement with DSC and
POM experiments.
Fig. 8. (a) Temperature dependence of UV–vis spectra of the A1 at the following
temperatures: 25, 50, 70, 75, 80, 100, 120, 130, 132, 135, 139, 145 ◦C. Inset: UV–vis
spectrum of the A1 in 25 ◦C (black curve) and deconvoluted (red curve), (b) temper-
ature dependence of UV–vis spectra of the A3 at the following temperatures: 25, 50,
75, 90, 100, 103, 105, and 110 ◦C. The isosbestic points: I, II, and III.
tion spectra when the terminal chain is varied can be attributed
to the modification of the star-shaped azomethines chain
planarity.
The temperature dependence of the UV–vis spectra was mea-
sured for thin film on the quartz (film cast from chloroform) in a
temperature range from the room temperature to clearing point in
the heating process. Fig. 8 shows the temperature dependence of
the UV–vis spectra of the A1 and A3 in a temperature range from
the room temperature to clearing point in the heating process.
Using UV–vis spectroscopy to monitor the changes in spectro-
scopic properties of the A1 and A3 during heating, we observed two
or three changes in the position of the isosbestic point, indicating
Absorption spectra of A1 for temperatures 25, 50, 70 and 75 ◦C
revealed the vibronic progressions in absorption band and were
the clearly visible in room temperature measurement (Fig. 8a).
To precisely find the positions of these vibronic bands the sec-
ond derivatives method was used. Then vibronic progressions
Table 4
UV–vis absorption characteristic of the A1.
Temp. [◦C]
ꢁ1 [nm]
ꢁ2 [nm]
ꢁ3 [nm]
ꢁ4 [nm]
25
50
70
75
80
100
120
130
135
139
145
225.0*
223.5*
223.0*
223.5*
229.0*
230.0*
231.0*
230.5*
230.5*
230.5*
230.0*
273.0d
268.5d
269.0d
270.0d
276.0*
279.5*
281.5*
281.5*
283.0*
282.0*
281.5*
284.5d
284.0d
283.5d
284.0d
294.0d
293.0d
292.5d
292.5d
Table 5
Phase transition temperature (◦C) of the A1 and the A1 composition with PMMA.
–
–
–
–
–
–
–
–
–
–
–
–
Code
Phase transitions, heating
Tg [◦C]
Tm [◦C]
ꢃH [J/g]
A1
8.0
25.7
28.7
20.0, 25.0; 84.4, 86.2; 136.2
33.5, 37.4; 56.9
40.1, 48.6; 70.5
9.3; 18.74; 1.53
12.9; 6.15
4.10; 1.34
A1/PMMA (fibers)
A1/PMMA (blend)
d, vibronic bands (deconvoluted).
Tg of neat PMMA 114 ◦C, Tg of PMMA fibers 110.9 ◦C.
*
Bands found due to second derivative method.

A. Iwan et al. / Spectrochimica Acta Part A 75 (2010) 891–900
899
Fig. 10. Polarizing microscope photographs of the PMMA fibers (left side) and A1/PMMA fibers (right side) at room temperature.
of the bands were deconvoluted with the modified Fourier self-
deconvolution and Finite Response Operator (FIRO) methods [10]
and it appeared that each of these bands was superposition of three
bands (ꢁ2, ꢁ3, and ꢁ4) clearly seen in Fig. 8a (inset). The wavelengths
of these peaks are marked by italics* in Table 4. In the case of absorp-
tion spectra for higher temperatures any vibronic progression were
not seen. The vibronic progression, seen in the absorption band, for
lower temperatures reveals the electron–phonon interaction con-
nected with the benzene ring stretching mode with the energy of
about 0.2 eV [11]. These vibronic bands were not seen in the case
of absorption spectra in higher temperatures probably because of
the delocalisation in these temperatures.
In UV–vis spectra of the A3 the hipochromic effect along with
the increase in the temperature was observed (Fig. 8b). No changes
in maximum of absorption band during heating of the A3 from 25
to 110 ◦C were found (Fig. 8b). In the UV–vis spectra of the A3 dur-
ing heating three isosbestic points were observed (Fig. 8b). First at
255 nm due to the increase in the temperature from 25 to 75 ◦C, sec-
ond at 320 nm appears also in the temperature range 25–75 ◦C and
was about 65 nm red shift in comparison with the first isosbestic
point. The third isosbestic point observed at 388 nm (75–110 ◦C)
was 68 nm red shifts in comparison with the second isosbestic
point. The first and second isosbestic points probably correspond
to the transition Cr to SmX, while the third isosbestic point cor-
responds to the transition SmX-Isotropisation. These observations
are in agreement with DSC and POM experiments.
atures of the compositions as determined by DSC are summarized
in Table 5.
As we see from Fig. 9 and Table 5 during heating of the A1 (pow-
der) at 10◦/min temperature of glass transitions (Tg) at 8.00 ◦C was
found along with four melting endotherms and the isotropisation
at 136.2 ◦C. Fibers of the A1/PMMA detected by DSC showed Tg at
about 25.7 ◦C and three broad melting endotherms (see Table 5,
Fig. 9 curve b). A1/PMMA blend exhibited Tg at 28.7 ◦C and simi-
lar as fibers of the A1/PMMA only three endotherms being better
seen than for fibers (see Fig. 9). The Tg of the A1/PMMA fibers was
higher than Tg of A1 and lower than Tg of the PMMA fibers. Similar
behavior of the A1/PMMA blend was detected. Photomicrographs
of the optical textures of PMMA and A1/PMMA fibers obtained by
electro-spinning at room temperature are presented in Fig. 10. This
part of our work needs more investigations.
4. Conclusion
In summary, we prepared three star-shaped azomethines
containing mesogenic unit by the condensation of tris(2-
aminoethyl)amine with aliphatic and aromatic aldehydes.
The following conclusions can be drawn from the present work:
1. The molecular structures of the star-shaped azomethines were
identified by FTIR, NMR and elemental analysis, and the results
were in accordance with the expected molecular formula.
2. All of the compounds were semi-crystalline. The values of melt-
ing point were in the range of 79–98 ◦C.
3.7. Thermal properties of A1/PMMA fibers and blend
3. Two star-shaped azomethines having as a terminal groups
alkoxysemiperfluorinated (–O–(CH2)3–(CF2)7–CF3) or two
phenyl rings (–Ph–Ph–) showed the smectic mesomorphism.
The mesophase of the A1 has been designated to be SmA phase.
A2 did not exhibit LC behavior and crystallized in the form of
beautiful spherulites.
4. Mesomorphic properties of the A1 were also studied by FTIR(T)
and UV–vis(T).
5. Thermal properties of the star-shaped azomethine A1 were pre-
liminarily studied via electro-spinning technique.
Recently, the electro-spinning technique has attracted a great
deal of attention as it is an effective means to produce nonwo-
ven membranes of nanofibers [12]. An important characteristic of
electro-spinning is the ability to make fibers with diameters in the
range of nanometers to a few micrometers. For these reasons, most
of the electro-spinning research was focused on the development of
nanofiber membranes as new materials for applications [12]. How-
ever, an increasing number of papers have also dealt with many of
the fundamental physical parameters [12]. Nanofibers can be used,
for example, for filtration of submicrometer particles in the sep-
aration industries and biomedical applications. Additionally, the
nanofibers can be used in photonics, sensorics, pharmacy, drug
delivery, catalyst supports, fiber templates for the preparation of
functional nanotubes and also in devices such as stealth planes and
others.
Synthesis and investigation of new mesogens is one of the impor-
tant and interesting fields for materials research community.
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of A1/PMMA are presented in Fig. 9. Details of transition temper-
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