Synthesis and characterization of symmetrical banana shaped liquid crystalline polyethers

Article abstract of DOI:10.1016/j.molstruc.2009.06.019

A series of banana shaped allyl terminated liquid crystalline bis{[4′(10-undecenoyloxy)-1,1′biphenyl-4-carboxylate}s varied with H, COOCH₃, Cl and NO₂ substituents in the central phenyl ring were synthesized and characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy. Effect of substituents on the mesomorphic property was examined by polarized optical microscopy (POM) and exhibited B₁ and nematic mesophases. Differential scanning calorimetry (DSC) measurements confirmed the LC property. Allyl group in the terminal position was epoxidized and polymerized to get banana shaped liquid crystalline ladder polyethers by ring opening polymerization and characterized spectroscopically. POM investigations displayed the development of enantiotropic grainy textures for polyethers and confirmed by DSC. Thermogravimetric analysis revealed that they were decomposed at high temperatures with good char yield.

Full text of DOI:10.1016/j.molstruc.2009.06.019

Journal of Molecular Structure 934 (2009) 44–52
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and characterization of symmetrical banana shaped liquid crystalline
polyethers
*
S. Balamurugan, P. Kannan
Department of Chemistry, Anna University, Sardar Patel Road, Chennai 600 025, India
a r t i c l e i n f o
a b s t r a c t
A series of banana shaped allyl terminated liquid crystalline bis{[40(10-undecenoyloxy)-1,10biphenyl-4-
carboxylate}s varied with H, COOCH3, Cl and NO2 substituents in the central phenyl ring were synthe-
sized and characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. Effect of substituents on the
mesomorphic property was examined by polarized optical microscopy (POM) and exhibited B1 and
nematic mesophases. Differential scanning calorimetry (DSC) measurements confirmed the LC property.
Allyl group in the terminal position was epoxidized and polymerized to get banana shaped liquid crys-
talline ladder polyethers by ring opening polymerization and characterized spectroscopically. POM inves-
tigations displayed the development of enantiotropic grainy textures for polyethers and confirmed by
DSC. Thermogravimetric analysis revealed that they were decomposed at high temperatures with good
char yield.
Article history:
Received 20 February 2009
Received in revised form 12 June 2009
Accepted 15 June 2009
Available online 21 June 2009
Keywords:
Banana shaped liquid crystal
B1 phase
Nematic phase
Ring opening polymerization
Ladder polyether
Thermal stability
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
piezo, pyroelectricity and second-order nonlinear optical activity.
Especially ferroelectric (FE) and antiferroelectric (AF) liquid crys-
Thermotropic liquid crystals are formed by calamitic or discotic
liquid crystals, wherein both exhibit nematic phase, calamitic mes-
ogen constitute smectic (laminar) while discotic imprint columnar
phase [1–6]. One of the most exiting developments in liquid crystal
research in the past few years was the discovery of ferroelectricity
and antiferroelectricity in liquid crystal with a non-chiral banana
shaped molecular structure by Noiri et al. [7–10]. The polar order
of bent molecule in smectic layer can induce chirality of smectic
layer, although the individual molecule is achiral; it seems that
the bent or banana shaped liquid crystal induce new sub-field of
liquid crystals. Such new materials, consisting of achiral molecule,
can be packed in smectic chiral layer by different ways which in
turn produces a diversified mesophases, namely B mesophases
[11–14]. They are designated as B1–B7, wherein some of them
exhibit unusual physical properties [15–17], like B2, B5 and B7
phases render electro-optical switching property. The high-tem-
perature smectic B1 phase formed at lower chain homolog whereas
switchable B2 phase attributed to longer-chained homolog
[18–19]. The low-temperature phases of the same compounds
are designated as B3 or B4.
talline materials are of interest, because they can be rapidly
switched between different states by external electrical field [21–
22]. Most of the bent-shaped mesogens are based on 1,3-pheny-
lene unit in the central core. The liquid crystalline polymers (LCPs)
combine the typical features of polymers and their application as
organic switching in external fields [23]. The first report on bent-
core main chain liquid crystalline polymers has been appeared
recently [24]. It was found that lateral substitution in the core
and in outer rings influences the formation and different type of
mesophases. Structure–property relationships on banana-shaped
mesogens have also recently been summarized [25]. Number of
banana-shaped liquid crystals reported based on five-ring sym-
metrical [26] and unsymmetrical [27] derived from resorcinol.
The structural modification of bent-core molecules achieved by
introducing various lateral substituents such as H, COOCH3, Cl, and
NO2 group into the central 1,3-phenylene ring at 2 and 4 positions
would furnish different materials that in turn may help to empa-
thize the relation between molecular structure and thermal behav-
ior. Herein, we report the influence of chemical variations on
central ring and connecting group of terminal chain with ester link
containing bent-core mesogenic molecules. The linking group at
the terminal chain to mesogen implies a major role in the forma-
tion of mesophases and transition temperatures. The terminal allyl
group was epoxidized to get banana shaped liquid crystalline
monomers succeeded ladder type polyethers by ring opening
polymerization and characterized.
Recently, several low molecular mass bent-core liquid crystals
have been synthesized and characterized [20]. They possess mac-
roscopic polar order with variety of useful properties, such as
* Corresponding author. Tel.: +91 44 2220 3155; fax: +91 44 2220 0660.
E-mail address: pakannan@annauniv.edu (P. Kannan).
0022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.06.019

S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
45
(75 MHz, CDCl3): d = 176.0, 172.1, 150.7, 144.0, 139.0, 137.5,
130.2, 129.6, 128.5, 121.99, 115.9, 33. 6, 29.1, 29.0, 24.8. IR (KBr):
3045 (alkeneACHA), 2926(ACHA), 2852 (AOHA), 1685(AC@O),
1641(AC@CA).
2. Experimental
2.1. Materials
Benzene, methanol, ethanol, dichloromethane and acetone
were purified by the reported procedure [28,29]. HBr 47% (SRL),
1,6-hexanediol (Merck), potassium hydroxide, sodium hydroxide,
potassium carbonate, hydrochloric acid (Merck, Mumbai), 4-
hydroxybenzoic acid (Spectrochem, India), BF3-etharate (SD fine),
N,N-dicyclohexylcarbodiimide (DCC) (Aldrich), 4-(dimethyl-
amino)pyridine (DMAP) (Aldrich), hydroquinone (SRL, India) and
3-chloroperbenzoic acid (Aldrich) were used as received.
2.5. Synthesis of 1,3-substituted phenylene bis{[40-(10-
undecenoyloxy)-1,10-biphenyl-4-carboxylate}s (ia–ie)
A typical procedure for the synthesis of ia is as follows: 4-(10-
undecenoyloxy)-1-biphenyl-4-carboxylic acid (0.0038 mol), resor-
cinol
(0.0019 mol)
and
dicyclohexylcarbodiimide
(DCC)
(0.0087 mol) were dissolved in dry dichloromethane (25 ml), to
this solution 4-(dimethylamino)pyridine (DMAP; 0.005 mol) added
and then stirred at room temperature for 5 h. The precipitate thus
obtained was removed by filtration and the precipitate was dis-
solved in dichloromethane and filtered. The filtrate was washed
with 5% HCl (3 ꢁ 50 ml), saturated NaCl (3 ꢁ 50 ml), and followed
by water. The separated organic layer was dried over anhydrous
sodium sulphate and solvent removed under reduced pressure.
The product was purified by column chromatography using chloro-
form as eluent, and recrystallized from ethanol to give white solid
(yield 85%). The above synthetic procedure was adopted for all
other homologs and the analytical data presented as follows:
ia: 1H NMR(400 MHz, CDCl3, d): 1.31–1.37 (m, 10H, ACH2A),
1.64–1.69 (m, 2H, ACH2A), 2.02–2.14 (m, 2H, ACH2A), 2.86 (t,
2H, ACH2A), 4.96 (dd, 1H, ACHA), 5.02 (dd, 1H, ACH), 5.78 (dd,
1H, ACHA), 7.06 (s, 1H, ArH), 7.16 (d, 2H, ArH), 7.63 (d, 5H, ArH),
8.08 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3): d = 172.1, 165.3,
150.7, 139.0, 137.5, 130.2, 129.6, 129.2, 128.5, 121.9, 118.4,
115.9, 115.1, 33.6, 29.1, 29.0, 24.8. IR (KBr): 3046 (alkeneACHA),
2926(ACHA), 1721(AC@O), 1642 (AC@CA).
2.2. Measurements
The inherent viscosity of polymers was determined using Ubbe-
lohde viscometer using chloroform as solvent at 30 °C. Elemental
analysis was carried out on a Carlo-Erba 1106 system. Infrared
spectra were obtained on a Thermo Electron Corporation Nicolet
380 FT-IR spectrometer. 1H NMR (400 MHz) and 13C NMR
(100 MHz) were recorded on a Bruker AM-400 spectrometer with
Me3Si (1H NMR) as internal standard and in CDCl3. Differential
scanning calorimetry (DSC) was conducted on a Perkin–Elmer
model DSC Pyris 1 system calibrated with indium and zinc stan-
dards. Dynamic thermogravimetric analysis was performed on Per-
kin–Elmer model TGA Pyris 1 system on film or powder samples at
a heating rate of 20 °C/min in Nitrogen. The polarizing microscope
study was performed using Euromex polarizing optical microscope
(POM) with an image analyzer equipped with Linkem HFS91 heat-
ing stage and a TP-93 temperature programmer. Samples were
placed between two thin microscopic slides. The textures were
observed during heating and cooling at the rate of 5 °C minꢀ1 with
the magnification of 20ꢁ. The photographs were taken with a
Nikon FM 10 camera and printed on a Konica film.
ib: (Yield 83%) 1H NMR(400 MHz, CDCl3, d): 1.31–1.37 (m, 10H,
ACH2A), 1.62–1.68 (m, 2H, ACH2A), 2.01–2.15 (m, 2H, ACH2A),
2.85 (t, 2H, ACH2A), 83.94 (s, 3H, ArH), 4.95 (dd, 1H, ACHA),
5.07 (dd, 1H, ACH), 5.76 (dd, 1H, ACHA), 7.03 (s, 1H, ArH), 7.17
(d, 1H, ArH), 7.64 (d, 5H, ArH), 8.08 (d, 2H, ArH). 13C NMR
(75 MHz, CDCl3): d = 172.1, 166.0, 165.3, 150.7, 139.0, 137.5,
130.2, 129.6, 129.2, 128.5, 121.9, 117.4, 115.9, 115.1, 51.5, 33.6,
29.1, 29.0, 24.8. IR (KBr): 3046 (alkeneACHA), 2926(ACHA),
1720(AC@O), 1642(AC@CA).
2.3. Synthesis of 10-undecenoyl chloride (1)
10-Undecenoic acid (0.2117 mol) was dissolved in benzene
(150 ml) with one drop of dimethylformamide, then thionyl chlo-
ride (75 ml; 0.6351 mol) added drop wise to the reaction mixture.
The resultant mixture was refluxed for 6 h with constant stirring.
The benzene and excess thionyl chloride were removed under vac-
uum to get acid chloride as colorless liquid [30] (yield 95%). 1H
NMR(400 MHz, CDCl3, d): 1.31–1.38 (m, 10H, ACH2A), 1.62–1.69
(m, 2H, ACH2A), 2.01–2.14 (m, 2H, ACH2A), 2.87 (t, 2H, ACH2A),
4.97 (dd, 1H, ACHA), 5.05 (dd, 1H, ACH), 5.75 (dd, 1H, ACHA).
13C NMR (75 MHz, CDCl3): d = 172.1, 137.2, 115.9, 46.9, 33.5,
29.6, 28.1, 25.2. IR (KBr): 3046 (alkeneACHA), 1799(ACACl),
2926(ACHA), 1718(AC@O). 1643(AC@CA).
ic: (Yield 82%) 1H NMR(400 MHz, CDCl3, d): 1.31–1.38 (m, 10H,
ACH2A), 1.62–1.69 (m, 2H, ACH2A), 2.01–2.14 (m, 2H, ACH2A),
2.87 (t, 2H, ACH2A), 4.97 (dd, 1H, ACHA), 5.05 (dd, 1H, ACH),
5.75 (dd, 1H, ACHA), 7.02(s, 1H, ArH), 7.16 (d, 1H, ArH), 7.62 (d,
5H, ArH), 8.09 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3): d = 172.1,
165.3, 150.7, 139.0, 137.5, 130.2, 129.6, 129.2, 128.5, 121.9,
119.0, 115.9, 115.1, 33.6, 29.1, 29.0, 24.8. IR (KBr): 3046 (al-
keneACHA), 2926(ACHA), 1790 (AArAClA), 1720(AC@O), 1643
(AC@CA).
id: (Yield 85%) 1H NMR(400 MHz, CDCl3, d): 1.32–1.38 (m, 10H,
ACH2A), 1.62–1.68 (m, 2H, ACH2A), 2.01–2.13 (m, 2H, ACH2A),
2.86 (t, 2H, ACH2A), 4.96 (dd, 1H, ACHA), 5.04 (dd, 1H, ACH),
5.76 (dd, 1H, ACHA), 7.14 (d, 2H, ArH), 7.61 (d, 5H, ArH), 8.05 (d,
2H, ArH). 13C NMR (75 MHz, CDCl3): d = 172.1, 165.3, 150.7,
139.0, 137.5, 130.2, 129.6, 129.2, 128.5, 121.9, 118.4, 115.9,
114.6, 33.6, 29.1, 29.0, 24.8. IR (KBr): 3046 (alkeneACHA),
2928(ACHA), 1722(AC@O), 1641 (AC@CA), 1525 (asymmetric–
Nitro).
2.4. Synthesis of 4-(10-undecenoyloxy)-1-biphenyl-4-carboxylic acid
(2)
10-Undecenoyl chloride (0.1 mol) diluted with dry tetrahydro-
furan (100 ml) and 4-hydroxybiphenyl-4-carboxylic acid
(0.1 mol) followed by dry triethylamine (0.12 mol) were added
and stirred at 20 °C for 12 h under nitrogen atmosphere. The pre-
cipitated triethylamine hydrochloride was removed and product
was dissolved in THF and filtered. The filtrate was evaporated
under vacuum to get crude product then recrystallized in ethanol
yield white crystals (yield 92%) [31]. 1H NMR(400 MHz, CDCl3, d):
1.32–1.38 (m, 10H, ACH2A), 1.62–1.69 (m, 2H, ACH2A), 2.05–
2.14 (m, 2H, ACH2A), 2.81 (t, 2H, ACH2A), 4.97 (dd, 1H, ACHA),
5.08 (dd, 1H, ACH), 5.76 (dd, 1H, ACHA), 7.15 (d, 2H, ArH), 7.63
(d, 4H, ArH), 8.02 (d, 2H, ArH), 11.05 (s.1H, ACOOH). 13C NMR
ie: (Yield 80%) 1H NMR(400 MHz, CDCl3, d): 1.31–1.38 (m, 10H,
ACH2A), 1.62–1.69 (m, 2H, ACH2A), 2.01–2.14 (m, 2H, ACH2A),
2.87 (t, 2H, ACH2A), 3.92 (s, 3H, ACH3), 4.97 (dd, 1H, ACHA),
5.05 (dd, 1H, ACH), 5.75 (dd, 1H, ACHA), 7.16 (d, 1H, ArH), 7.62
(d, 5H, ArH), 8.09 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3):
d = 172.1, 166.0, 165.3, 150.7, 139.0, 137.5, 130.2, 129.6, 129.2,
128.5, 121.9, 117.8, 115.9, 114.6, 51.5, 33.6, 29.1, 29.0, 24.8. IR

46
S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
Scheme 1. Synthesis of monomers and polymers Ia–Ie.
Scheme 2. Molecular modeling of ladder type banana shaped polyethers.

S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
47
Table 1
Yield, viscosity, solubility and elemental analysis of polymer Ia–Ie.
a
Polymer
Yield (%)
ginh (dL/g)
Solubilityb
DMF CHCl3/DCM
+/+
Emp. formula
Elemental analysis
Acetone
MeOH/EtOH/Benzene
Calc. Found
C
H
N
–
Ia
Ib
Ic
Id
Ie
88
87
89
85
90
0.81
0.89
0.85
0.83
0.87
ꢀ/+
ꢀ/ꢀ
(C54H60O10
)
)
Calc.
Found
Calc.
Found
Calc.
Found
Calc.
Found
Calc.
Found
74.63
74.25
72.55
72.06
71.79
71.55
70.96
70.70
69.19
69.08
6.96
6.82
6.74
6.70
6.58
6.44
6.51
6.38
6.33
6.27
n
+/+
+/+
+/+
+/+
ꢀ/+
ꢀ/+
ꢀ/+
ꢀ/+
ꢀ/ꢀ
ꢀ/ꢀ
ꢀ/ꢀ
ꢀ/ꢀ
(C56H62O12
–
–
n
(C54H59ClO10
)
n
(C54H59NO12
)
1.53
1.46
1.44
1.41
n
(C56H61NO14
)
n
a
Measured at 30 °C with c = 0.2 g/dL in chloroform.
Solubility (0.05 g in 10 ml). +/+, soluble at room temperature; ꢀ/+, soluble at heating; ꢀ/ꢀ, insoluble.
b
(KBr): 3046 (alkeneACHA), 2926(ACHA), 1722(AC@O), 1643
(AC@CA), 1527 (asymmetric–Nitro).
2.6. Synthesis of 1,3-substituted phenylene bis{[40-(10-
epoxyundecyloxy)-1,10-biphenyl-4-carboxylate}s
A solution of 1,3-phenylene bis{[40-(10-undecenoyloxy)-1,10-
biphenyl-4-carboxylate} (ia; 0.001 mol) and pure 3-chloroperben-
zoic acid (0.00017 mol) dissolved in dry dichloromethane (30 ml)
and stirred at room temperature for 24 h. The dichloromethane
solution was extracted successively with 5% aqueous solution of
Na2SO4 (3 ꢁ 20 ml), 5% aqueous Na2CO3 (3 ꢁ 20 ml), and concen-
trated aqueous NaCl (3 ꢁ 20 ml) solution. After drying over MgSO4,
dichloromethane evaporated under vacuum gave corresponding
epoxy monomer as white solid which was polymerized in situ
without further purification. A similar procedure was adopted for
the preparation of remaining monomers.
Fig. 1. FT-IR spectrum of ia and Ia.
Fig. 2. 1H NMR spectrum of ia.

48
S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
2.7. Synthesis of poly{1,3-phenylenebis{[40-(9-(2-oxiranoyloxy)-1,10-
biphenyl-4-carboxylate}s (Ia–Ie)
ACH), 5.73 (dd, 1H, ACHA), 7.08(s, 1H, ArH), 7.15 (d, 1H, ArH),
7.62 (d, 5H, ArH), 8.05 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3):
d = 172.1, 165.3, 150.7, 139.0, 137.5, 130.2, 129.6, 129.2, 128.5,
121.9, 119.0, 115.9, 115.1, 33.6, 29.1, 29.0, 24.8. IR (KBr): 3046 (al-
keneACHA), 2924(ACHA), 1790 (AArAClA), 1720(AC@O),
1247(CAOAC).
A typical procedure for the synthesis of Ia is as follows: 1,3-phe-
nylene
bis{[40-(10-epoxyundecyloxy)-1,10-biphenyl-4-carboxyl-
ate} (0.001 mol) was dissolved in dry dichloromethane (5 ml) and
0.1 ml of BF3-etharate added and stirred at room temperature for
24 h under nitrogen atmosphere. At the end of reaction, mixture
was concentrated, and poured in to dry methanol (100 ml). A white
colored precipitate formed was purified by reprecipitation using
chloroform–methanol, filtered and dried in vacuum oven at 75 °C
(Yield 88%). This synthetic procedure was adopted for the synthesis
of remaining polymers and the analytical data presented as
follows:
Polymer Id: (Yield 85%) 1H NMR(400 MHz, CDCl3, d): 1.32–1.38
(m, 10H, ACH2A), 1.62–1.69 (m, 2H, ACH2A), 2.02–2.14 (m, 2H,
ACH2A), 2.87 (t, 2H, ACH2A), 4.97 (dd, 1H, ACHA), 5.05 (dd, 1H,
ACH), 5.77 (dd, 1H, ACHA), 7.16 (d, 2H, ArH), 7.62 (d, 5H, ArH),
8.09 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3): d = 172.1, 165.3,
150.7, 139.0, 137.5, 130.2, 129.6, 129.2, 128.5, 121.9, 118.4,
115.9, 114.6, 33.6, 29.1, 29.0, 24.8. IR (KBr): 3046 (alkeneACHA),
2925(ACHA), 1720(AC@O), 1244(CAOAC), 1528 (asymmetric–
Nitro).
Polymer Ia: 1H NMR (400 MHz, CDCl3, d): 1.32–1.36 (m, 10H,
ACH2A), 1.62–1.68 (m, 2H, ACH2A), 2.01–2.16 (m, 2H, ACH2A),
2.88 (t, 2H, ACH2A), 4.96 (dd, 1H, ACHA), 5.05 (dd, 1H, ACH),
5.75 (dd, 1H, ACHA), 7.01(s, 1H, ArH), 7.15 (d, 2H, ArH), 7.64 (d,
5H, ArH), 8.08 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3): d = 172.1,
165.3, 150.7, 139.0, 137.5, 130.2, 129.6, 129.2, 128.5, 121.9,
118.4, 115.9, 115.1, 33.6, 29.1, 29.0, 24.8. IR (KBr): 2925(ACHA),
1720(AC@O), 1247(CAOAC).
Polymer Ie: (Yield 90%) 1H NMR(400 MHz, CDCl3, d): 1.31–1.36
(m, 10H, ACH2A), 1.62–1.69 (m, 2H, ACH2A), 2.01–2.16 (m, 2H,
ACH2A), 2.87 (t, 2H, ACH2A), 3.95 (s, 3H, ACH3), 4.97 (dd, 1H,
ACHA), 5.08 (dd, 1H, ACH), 5.75 (dd, 1H, ACHA), 7.19 (d, 1H,
ArH), 7.62 (d, 5H, ArH), 8.10 (d, 2H, ArH). 13C NMR (75 MHz,
CDCl3): d = 172.1, 166.0, 165.3, 150.7, 139.0, 137.5, 130.2, 129.6,
129.2, 128.5, 121.9, 117.8, 115.9, 114.6, 51.5, 33.6, 29.1, 29.0,
24.8. IR (KBr): 3046 (alkeneACHA), 2926(ACHA), 1722(AC@O),
1248(CAOAC), 1527 (asymmetric–Nitro).
Polymer Ib: (Yield 87%) 1H NMR (400 MHz, CDCl3, d): 1.31–1.38
(m, 10H, ACH2A), 1.62–1.69 (m, 2H, ACH2A), 2.01–2.14 (m, 2H,
ACH2A), 2.87 (t, 2H, ACH2A), 4.97 (dd, 1H, ACHA), 5.05 (dd, 1H,
ACH), 5.75 (dd, 1H, ACHA), 7.02(s, 1H, ArH), 7.16 (d, 2H, ArH),
7.62 (d, 5H, ArH), 8.09 (d, 2H, ArH). 13C NMR (75 MHz, CDCl3):
d = 172.1, 165.3, 150.7, 139.0, 137.5, 130.2, 129.6, 129.2, 128.5,
121.9, 118.4, 115.9, 115.1, 33.6, 29.1, 29.0, 24.8. IR (KBr):
2926(ACHA), 1720(AC@O), 1248(CAOAC).
3. Results and discussion
3.1. Synthesis
The banana shaped 1,3-substituted phenylene bis{[40-(10-
undecenoyloxy)-1,10-biphenyl-4-carboxylate}s were prepared and
then epoxidized to get the monomers and polymers (Scheme 1).
The allyl terminated banana shaped precursors were studied for
Polymer Ic: (Yield 89%) 1H NMR(400 MHz, CDCl3, d): 1.33–1.38
(m, 10H, ACH2A), 1.63–1.69 (m, 2H, ACH2A), 2.01–2.14 (m, 2H,
ACH2A), 2.85 (t, 2H, ACH2A), 4.97 (dd, 1H, ACHA), 5.07 (dd, 1H,
Fig. 3. 13C NMR spectrum of ia.

S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
49
Fig. 4. 1H NMR spectrum of Ia.
their POM investigation based on their better chemical stability
than their epoxy counterparts. The polyethers (Scheme 2) were
synthesized by epoxidation of allyl group followed by ring opening
polymerization in the presence of BF3-etherate as an initiator. The
polymers are soluble in DMF, CHCl3, CH2Cl2, and acetone and insol-
uble in methanol, ethanol, 2-propanol, benzene and toluene (Table
1). The intrinsic viscosity of the polymers was determined using an
Ubbelohde viscometer using chloroform as solvent at 30 °C and
data shown in Table 1. The inherent viscosity was in the range of
0.81–0.89 dL/g. The data reveals that they are of reasonably high
molecular weight materials.
5.75 ppm. The 13C NMR spectrum of ia is shown in Fig. 3. The
C@O signal of ester group at 165.3 ppm, the aliphatic protons are
appeared in the range of 33.6–24.8 ppm and aromatic protons res-
onated in the range of 115.1–172.1 ppm. 1H NMR spectrum Ia is
shown in Fig. 4, the disappearance of olefinic protons shows the
formation of polymer. All the polymers displayed similar FT-IR,
1H and 13C NMR spectra. The elemental analysis values obtained
for Ia–Ie are in accordance with the calculated values and listed
in Table 1.
3.2. Mesophases and thermal properties of precursors ia–ie
The structures of ia–ie and Ia–Ie were confirmed by FT-IR, 1H
and 13C NMR, and elemental analysis. The spectral values are in
accordance with the assigned structures. The representative FT-IR
spectrum of ia and Ia is shown in Fig. 1. The strong absorption
bands at 3046, and 1643 cmꢀ1 corresponds to alkeneACAH, and
AC@CA stretchings respectively and these two absorptions are dis-
appeared in Ia ascribed to completeness of polymerization. The
bands appearing at 2926 and 1722 cmꢀ1 as a result of asymmetric
stretching of methylene spacers and carbonyl (C@O) stretching,
respectively. The alky and aryl ether stretching appeared around
1253 cmꢀ1. The absorption around 832–727 cmꢀ1 represents to
aromatic ring vibrations.
The transition temperatures and associated enthalpy values for
ia–ie are summarized in Table 2. They differ from one another with
respect to substituents (H, Cl, NO2, and COOCH3) in 2 and 4 posi-
tion of central phenyl ring. The ia, ic and id shows enantiotropic
B1 phase on cooling from isotropic liquid and there was no signif-
icant change in the mesophase on lowering the temperature. The
enthalpy value of isotropization was 11.38j/g with mesophase
duration (DT) of 71.9 °C, nevertheless, compound ib unable to ex-
hibit mesophase attributable to destabilization of substituent in
the center core. However, ie was displayed nematic phase on cool-
ing from isotropic temperature because of the presence of NO2
group which reduce the perturbation effect of COOCH3.
The DSC thermograms were measured at the rate of 5°C/min
with heating and cooling cycles, DSC curve of ia–ie shown in
Fig. 5 and phase transitions listed in Table 2. Except ib, the remain-
The representative 1H NMR spectrum of ia is illustrated in Fig. 2.
The aromatic protons of precursor were resonated in the range of
7.02–8.09 ppm and aliphatic protons resonated in the range of
1.31–2.87 ppm. Three olefinic protons resonated at 4.97, 5.05 and
Table 2
Transition temperatures (°C) and associated enthalpies (J/g) observed in DSC for ia–ie.
Precursor
R2/R4
Transition temperature (°C)
DT (°C)
Cr
B1
N
I
ia
ib
ic
id
ie
H/H
H/COOCH3
H/Cl
NO2/H
NO2/COOCH3
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
69.5 (3.83 J/g)
ꢂ
–
ꢂ
ꢂ
–
–
–
–
–
ꢂ
144.5 (11.38 J/g)
116 (16.32 J/g)
137 (9.8 J/g)
140 (10.56 J/g)
122 (9.85 J/g)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
75
–
38
21
44
99 (2.79 J/g)
119 (3.48 J/g)
78 (3.46 J/g)
Cr, crystalline phase, B1, columnar phase, N, nematic phase, I, isotropic liquids.

50
S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
ing precursors show two endothermic peaks corresponds to crys-
talline-liquid crystalline (Tm) and liquid crystalline–isotropic tran-
sition (Ti) respectively. The Tm of the series was observed in the
range of 69.5–144.5 °C. Fig. 6 shows correlation between the series
and transition temperatures (Tm and Ti) observed from DSC mea-
surement. The ia–ie indicate two endothermic peaks (except ib).
The ia exhibited large mesophase duration of 75 °C where as id dis-
played little mesophase duration of 21 °C.
3.3. Mesophase and thermal property of polymers Ia–Ie
The polymers Ia, Ic and Id were found to form grainy phases as
found in POM and the representative LC texture grainy phases
(Fig. 7). The polymer Ib and Ie substituted with methyl ester and
nitro group did not exhibit any LC phase. In case of polymer Ie,
the reason that do not show LC phase is attributed to the steric hin-
drance of NO2 and COOCH3 groups which could not provide mobil-
ity to the polymeric chain. But the same monomer (ie) exhibited LC
phase since the steric hindrance was nullified by each other (NO2
and COOCH3). The LC property of Ia, Ic and Id was evaluated with
DSC measurement and their thermograms of Ia, Ic and Id shown in
Fig. 8 and phase transition data given in Table 3. Here again, except
Ib and Ie, the remaining polymers evidenced three endothermic
peaks corresponds to glass transition temperature (Tg), cystalline-
liquid crystalline (Tm) and liquid crystalline–isotropic transition
(Ti) respectively.
Fig. 5. DSC thermograms of ia–ie.
The Tm of the series was observed in the range of 138–145 °C. In
general, Tg value of LCPs is influenced not only by the polymeric
chain flexibility but also the substitutents in the aromatic ring.
The POM observations confirmed (Fig. 7) the grainy LC phase was
formed between the temperature range of Tm and Ti in both cooling
and heating cycles. The transition observed under POM was found
to be in accordance with DSC results.
The thermal behavior of polyethers was evaluated by TGA
under nitrogen atmosphere at a heating rate of 10 °C/min; the
representative TGA thermogram of Ia shown in Fig. 9, the data
illustrated in Table 4. The thermal stability was evaluated by 5%
Fig. 6. Graphical representation of the phase transition temperatures of ia–ie.
Fig. 7. HOPM photographs of ia, ic, id and Ia at 20ꢁ magnifications.

S. Balamurugan, P. Kannan / Journal of Molecular Structure 934 (2009) 44–52
51
Table 4
TGA data of Ia–Ie.
Polymer
Temperature corresponding to
Carbon residue at 800 °C (%)
5% Weight loss
50% Weight loss
Ia
Ib
Ic
Id
Ie
327
302
345
316
325
440
438
456
432
437
20
22
27
31
24
polymers (Ia–Ie) were synthesized and characterized. The molecu-
lar structures were identified by FT-IR and NMR spectroscopy, and
are in accordance with the targeted molecular formula. The varia-
tions in substituents (H, COOCH3, Cl and NO2) on central phenyl
ring have been correlated with thermal and mesomorphic proper-
ties. The ia, ic and id have been designated as columnar B1 phase
and ie identified as nematic phase. The ia exhibited large meso-
phase duration. The Ia, Ic and Id shows a grainy phase on heating
and cooling, whereas Ib and Ie unable to show mesophases be-
cause of the steric hindrance of both the bulky groups (NO2 and
COOCH3) while the monomer ie showing LC phase in which the
steric hindrance was nullified resulted from the free mobility in
the molten state. All the polymers possess high Tg in the range of
78–110 °C. The thermal stability of the polymers increases in the
order as Ie > Ib > Ic > Id > Ia.
Fig. 8. DSC thermograms of Ia–Ie.
Table 3
DSC and POM data of Ia–Ie.
Polymer
DSC (°C)a
POM (°C)b
Tg
Tm
Ti
D
T
Tm
Ti
D
T
Mesophase
Ia
Ib
Ic
Id
Ie
78
138
159
145
141
162
175
–
181
169
-
37
–
36
28
–
136
160
142
138
160
175
–
180
168
–
39
–
38
30
–
Grainy
–
Grainy
Grainy
–
108
110
97
Acknowledgements
86
This research work was supported by University Grants Com-
mission, New Delhi, Government of India [F. 31-110/2005 (SR)]
and gratefully acknowledged.
a
Observed in POM during cooling cycle.
Obtained in DSC during heating cycle.
b
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and 50% weight loss at minimum temperature. The results
disclosed they were stable upto 302 °C and start degrading there-
after in nitrogen atmosphere. The thermal stability increases in
the order of the Ie > Ib > Ic > Id > Ia. The char yield was measured
at 800 °C and data shown in the Table 4. The polymers rendered
good char yield due to the presence of aromaticity.
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