Pendant triazole ring assisted mesogen containing side chain liquid crystalline polymethacrylates: Synthesis and characterization

Article abstract of DOI:10.1007/s12039-011-0061-z

Two series of click chemistry assisted alkoxymethyl-1H-[1,2,3]-triazol-1-yl containing sidechain liquid-crystalline polymethacrylates were synthesized by free radical polymerization technique. Mesogen was linked to backbone through various spacer units. Monomers and polymers were characterized by FT-IR, ¹H and ¹³C-NMR spectral techniques. Thermal stability of polymers was confirmed by thermogravimetric analysis. Mesomorphic property and phase transition temperature of polymers were analysed by differential scanning calorimetry and polarized optical microscopy. Phase transition temperature and mesomorphic property of polymers with respect to insertion of polar alkoxy group on terminal triazole ring and spacer length between backbone and mesogen were investigated. Polymers exhibited grainy like textures under polarized optical microscopy. Spacer length between mesogen and backbone alters phase transition temperature of the polymers. Indian Academy of Sciences.

Full text of DOI:10.1007/s12039-011-0061-z

J. Chem. Sci., Vol. 123, No. 1, January 2011, pp. 81–89. * Indian Academy of Sciences.
Pendant triazole ring assisted mesogen containing side chain liquid
crystalline polymethacrylates: Synthesis and characterization
T PALANI, C SARAVANAN and P KANNAN*
Department of Chemistry, Anna University, Chennai 600 025, India
e-mail: pakannan@annauniv.edu
MS received 28 November 2009; revised 5 September 2010; accepted 14 December 2010
Abstract. Two series of click chemistry assisted alkoxymethyl-1H-[1,2,3]-triazol-1-yl containing side-
chain liquid-crystalline polymethacrylates were synthesized by free radical polymerization technique.
Mesogen was linked to backbone through various spacer units. Monomers and polymers were characterized
by FT-IR, 1H and 13C-NMR spectral techniques. Thermal stability of polymers was confirmed by
thermogravimetric analysis. Mesomorphic property and phase transition temperature of polymers were
analysed by differential scanning calorimetry and polarized optical microscopy. Phase transition temperature
and mesomorphic property of polymers with respect to insertion of polar alkoxy group on terminal triazole
ring and spacer length between backbone and mesogen were investigated. Polymers exhibited grainy like
textures under polarized optical microscopy. Spacer length between mesogen and backbone alters phase
transition temperature of the polymers.
Keywords. Click chemistry; triazole; mesogen; liquid crystal polymers; polymethacrylates.
1. Introduction
property of the observed phases, because most of the
usual heteroatoms (S, O and N) introduced are
Side-chain liquid crystalline polymers (SC-LCPs) have chemically classified as more polarizable than
considerable interest in advanced electro-optic tech- carbon.13–15 However, it is important to extend
nology due to mesogenic side chain and low glass molecular design of liquid crystals to involve other
transition temperature.1 Craig et al. devised an empir- ring systems from not only theoretical, but also
ical rule in liquid crystalline property of various SC- practical point of view. Particularly, liquid crystalline
LCPs by keeping constant mesogenic group and spacer compounds containing five-membered heterocyclic
lengths and changing their backbone vice versa.2,3 rings have been successfully evaluated.16,17 It was
Various synthetic methods of SC-LCPs have been found that non-linear heterocyclic liquid crystals, such
reported in the literature with mesogenic groups such as pyrazole, furan, thiophene, and isoxazole derivatives
as 4-methoxybiphenyl, 4-cyanobiphenyl, and 4- with terminally positioned heterocyclic ring form
substituted phenyl benzoates.4,5 A number of neme- smectic or nematic phase at low temperature and in
togens were copolymerized with various azobenzene wide temperature range are well-studied.18,19 In addi-
containing side chain polymers for analysing their tion, presence of heteroatom has contributed to
photo alignment with respect to switching property of increasing molecular dipole and dielectric anisotropy.20
azobenzene unit.6–9 During the past decades large Compounds containing five-membered ring such as
number of liquid crystalline compounds containing [1,2,3]-triazole formed by [2+3] dipolar cycloaddition
heterocyclic units have been synthesized.10–12 Interest reaction between an organic azide and terminal alkyne,
in such compounds arises from incorporation of also known as ‘Click Chemistry’ has attracted much
heteroatoms can result in prominent changes in the attention in the field of materials chemistry21 organic
corresponding liquid crystalline phases and/or physical chemistry22, supramolecular chemistry9 and drug dis-
covery.23 Gallardo et al.12, have employed click chem-
*For correspondence
istry to synthesize number of non-linear heterocyclic
81

82
T Palani et al.
chiral liquid crystalline compounds with three and four- mixture was stirred for 24h at room temperature.
membered ring systems containing [1,2,3]-triazole ring Resultant solution was filtered, washed with water,
at a terminal position of rigid core and characterized brine and dried over anhydrous sodium sulphate.
their mesomorphic property. Compounds containing Crude product was purified by column chromatogra-
three–membered ring systems such as [1,2,3]-triazole phy (silica gel, hexane\ethyl acetate) to give monomer
ring at a terminal position was unable to exhibit liquid ia as colourless solid (yield: 64%): Since each series of
crystalline property.24 Nevertheless, introduction of polar monomers having same structural units with minor
alkoxy group through methylene carbon at the terminal changes in spacer lengths, representative spectral data
[1,2,3]-triazole ring of same three-membered ring provided for each series of monomers as follows.
systems displayed liquid crystallinity.25 Thus, the present
2.2a ia: FT-IR (KBr, cm−1): 2952 and 2876 (−CH2−),
work deals with synthesis of two homologous series of
2924 and 3039 (−C−CH3), 1615 (−C=CH2), 885 (o-
non-linear heterocyclic liquid crystalline polymers name-
ly, poly[4-(4-alkoxymethyl)-1H-1,2,3-triazole-1-yl-4-
methacryloyloxyalkyloxy benzoate]s using click chem-
istry with introduction of polar groups at terminal
position in the heterocyclic ring through methylene
group and investigated their mesomorphic property and
their structure–property relationships.
1
substituted aromatic), H NMR (400 MHz, CDCl3)δ:
8⋅15 (d, 2H, Ar), 7⋅98 (s, 1H, triazole-CH), 7⋅79 (s, 2H,
Ar), 7⋅39 (s, 2H, Ar), 6⋅98 (s, 2H, Ar), 6⋅10 (s, 1H, −
C=CH2), 5⋅55 (s, 2H, −C=CH2), 4⋅66 (s, 2H, triazole-
CH2−O−), 4⋅09 (s, 2H, Ar−O−CH2−), 3⋅85 (s, 3H, −
CH2−O−C(=O)−), 3⋅37 (s, 3H, −OCH3), 1⋅95−1⋅25 (m,
11H, −(CH2)4−, −CH3). 13CNMR (400MHz, CDCl3)δ:
183⋅6, 179⋅5 (carbonyl), 162⋅3, 161⋅7, 156⋅6, 142⋅2,
139⋅5, 134⋅9, 131⋅4, 130⋅9, 126⋅2, 125⋅4, 123⋅6, 122⋅1,
119⋅4, 117⋅6, 109⋅8 (aromatic), 71⋅3, 68⋅3, 65⋅8, 58⋅4
(−O−CH3, triazole-CH2−O, Ar−O−CH2−, −CH2−O−C
(=O)−), 32⋅9, 32⋅3, 29⋅8, 27⋅2, 24⋅9, 25⋅8, 24⋅4, 18⋅8,
11⋅6 (aliphatic).
2. Experimental
2.1 Materials
Methanol, ethanol, phenol, THF, diethyl ether, chloro-
form, triethylamine, dimethylformamide (DMF) (SRL,
India) and other solvents were purified by reported
procedures.26 Propargyl alcohol, p-aminophenol, 4-
hydroxybenzoic acid, dimethylsulfate and diethylsul-
fate and 2, 2′-azobisisobutyronitrile (AIBN) (Merck,
Germany) were used as received. Silica gel (MN
Kieselgel 100–200 mesh) was used for column chroma-
tography. Methacrylic acid, hydroquinone, and 1, 6-
hexanediol, 1, 8-octanediol, 1, 10-decanediol, (Fluka,
Switzerland) were used as supplied. 4-Azidophenol (1),
3-methoxy propa-1-yne (2), 3-Ethoxy prop-1-yne (3), 4-
[4-(methoxymethyl)-1H-[1,2,3]-triazol-1-yl]phenol (7),
4-[4-(ethoxymethyl)-1H-[1, 2, 3]-triazol-1-yl] phenol
(8)25, 6-Bromo-1-hexanol, 8-bromo-1-octanol, 10-
bromo-1-decanol, methacryloyl chloride27 were synthe-
sized by reported procedures.
2.2b iia: FT-IR (KBr, cm−1): 2958 and 2872 (−CH2−),
2931 and 3026 (−C−CH3), 1619 (−C=CH2), 891 (o-
1
substituted aromatic), H NMR (400 MHz, CDCl3)δ:
8⋅16 (d, 2H, Ar), 7⋅98 (s, 1H, triazole-CH), 7⋅77 (s, 2H,
Ar), 7⋅39 (s, 2H, Ar), 6⋅99 (s, 2H, Ar), 6⋅10 (s, 1H, −
C=CH2), 5⋅55 (s, 2H, −C=CH2), 4⋅65 (s, 2H, triazole-
CH2−O−), 4⋅08 (s, 2H, Ar−O−CH2−), 3⋅85 (s, 3H, −
CH2−O−C(=O)−), 3⋅34 (q, 2H, −OCH2−), 1⋅15−2⋅01
(m, 18H, −(CH2)4−, −CH3, −CH3). 13CNMR
(400 MHz, CDCl3)δ: 183⋅7, 179⋅5 (carbonyl), 162⋅8,
161⋅2, 157⋅2, 143⋅2, 138⋅9, 133⋅9, 132⋅4, 130⋅9, 126⋅7,
125⋅5, 123⋅6, 124⋅1, 118⋅6, 117⋅3, 109⋅1 (aromatic),
71⋅5, 68⋅6, 65⋅6, 60⋅4, 58⋅5 (Ar−O−CH2, −O−
CH2−CH3, triazole-CH2−O−, Ar−O−CH2−, −CH2−O−
C(=O)−), 32⋅5, 33⋅3, 30⋅8, 28⋅2, 26⋅9, 26⋅8, 25⋅4, 19⋅8,
13⋅6 (aliphatic).
2.2 Monomer ia–ic and iia–iic
Monomers were prepared using similar procedure from
the corresponding compounds. The typical procedure 2.3 Polymer Ia–IIc
for the synthesis of ia is as follows: Compound 7
(2⋅16g, 0⋅01mol) in dichloromethane was added under Polymers were synthesized by free-radical solution
nitrogen to a solution of compound 4 (3⋅43g, addition polymerization technique from the
0⋅01mol), DMAP (1⋅37g, 0⋅01mol) and DCC corresponding monomers using AIBN as an initiator
(2⋅31g, 0⋅01mol) in 100mL of absolute dichloro- in THF at 60°C for 48h. Typical procedure for the
methane under stirring. Subsequently, the reaction synthesis of polymer Ia is as follows: Monomer ia

Pendant triazole ring assisted mesogen
83
(400mg, 0⋅67mol) and AIBN (2wt.%) were dissolved Weight-average molecular weight (Mw), number-
average molecular weight (Mn) and polydispersity
(Mw=Mn) of polymers were obtained on a PL-GPC
model 210 chromatograph using DMF as eluent at
25°C and calibrated with polystyrene standard. Ther-
mogravimetric analysis was performed on a Mettler
TA3000 thermal analyzer in nitrogen atmosphere at a
heating rate of 20°C min−1 with a sample weight of
3−5mg. Transition temperatures and phase transition
enthalpies were determined by differential scanning
calorimetry (DSC) using a Perkin-Elmer DSC7 calo-
rimeter at a heating rate of 5°C per min. The liquid
crystalline textures were watched using a Euromex
polarizing microscope equipped with a Linkem
HFS91 heating stage and a TP93 temperature pro-
grammer. Samples were made by placing small
quantity of materials between two thin glass cover
slips, and the anisotropic behaviour observed by
heating and/or cooling at the rates of 5°C/min. The
photographs were taken with a Nikon FM10 camera
and exposed on a Konica film.
in dry THF and gentle steam of nitrogen purged into
the solution. The solution was kept in an oil bath at
60°C for 48h. Then the solution was cooled and
poured into excess of methanol to precipitate the
product. Crude polymer thus obtained was reprecipi-
tated twice using chloroform and methanol. Purified
polymer was dried at 45°C under vacuum for 48h
to afford colourless solid. Representative spectral
data provided for each series of polymers appended
below:
2.3a Ia: FT-IR (KBr, cm−1): 2946 and 2881 (−CH2−),
2921 and 3000 (−CH3), 1601 (aromatic −C=C−), 888 (o-
1
substituted aromatic), H NMR (400MHz, CDCl3)δ:
8⋅25 (s, 1H, triazole), 8⋅13 (s, 2H, Ar), 7⋅85 (s, 2H, Ar),
7⋅40 (s, 2H, Ar), 7⋅00 (s, 2H, Ar), 4⋅66 (s, 2H, triazole-
CH2−), 4⋅09 (Ar−O−CH2−), 3⋅38 (s, 5H, −OCH3, −CH2−
O−C(=O)−) 1⋅86−1⋅09 (m, 13H, −CH3, −(CH2)4−, −
CH2−). 13C NMR (400MHz, CDCl3)δ: 183⋅2, 179⋅5
(carbonyl), 161⋅7, 156⋅6, 142⋅2, 139⋅5, 132⋅2, 131⋅4,
126⋅2, 125⋅4, 122⋅1, 119⋅4, 109⋅8 (aromatic), 71⋅2, 68⋅3,
58⋅4 (−O−CH2, triazole-CH2−O, Ar−O−CH2−, −
CH2−O−C(=O)−), 32⋅9, 32⋅3, 29⋅8, 24⋅9, 24⋅4, 18⋅8,
11⋅6 (aliphatic).
3. Results and discussion
3.1 Synthesis
2.3b IIa: FT-IR (KBr, cm−1): 2948 and 2871 (−CH2−),
2919 and 3011 (−CH3), 1598 (aromatic −C=C−), 893
Two kinds of alkyloxy substituted click chemistry
assisted mesogen containing side liquid crystalline
polymethacrylates were synthesized by free radical
addition polymerization technique in THF solution
using AIBN as initiator at 60°C and influence of
substituent on the terminal position and spacer length
in the side chain on phase transition temperatures and
mesomorphic property were investigated. All polymers
were prepared by following synthetic routes as shown
in scheme 1.
1
(o-substituted aromatic), H NMR (400MHz, CDCl3)δ:
8⋅25 (s, 1H, triazole), 8⋅12 (s, 2H, Ar), 7⋅78 (s, 2H, Ar),
7⋅46 (s, 2H, Ar), 7⋅01 (s, 2H, Ar), 4⋅69 (s, 2H,
triazole-CH2−), 4⋅11 (Ar−O−CH2−), 3⋅40 (s, 5H, −
OCH3, −CH2−O−C(=O)−) 1⋅86−1⋅09 (m, 13H, −CH3,
−(CH2)4−, −CH2−, −CH3). 13CNMR (400MHz,
CDCl3)δ: 183⋅4, 179⋅8 (carbonyl), 161⋅9, 156⋅8,
142⋅4, 139⋅8, 132⋅2, 131⋅5, 126⋅7, 125⋅4, 122⋅1,
119⋅5, 109⋅4 (aromatic), 71⋅2, 68⋅5, 58⋅6 (−O−CH2,
triazole−CH2−O−, Ar−O−CH2−, −CH2−O−C(=O)−),
32⋅6, 32⋅4, 29⋅7, 24⋅6, 24⋅7, 18⋅6, 14⋅2, 12⋅8, 11⋅6,
(aliphatic).
Introduction of different spacers between back bone
and mesogenic unit enhanced the solubility of poly-
mers in common organic solvents such as chloroform,
dichloromethane, DMF and THF. Number average
molecular weight and polydispersity index value of
polymers were tabulated in table 1 and revealed that
the polymers possess moderate molecular weights.
Chemical structure of synthesized polymers was
2.4 Measurements
Chemical structure of intermediates and target confirmed by FT-IR, 1H and 13CNMR spectral
1
materials were analysed by infrared spectra obtained techniques. Figure 1 displays H-NMR spectrum of
from Bruker IFS 66V Fourier Transform spectrom- monomer iia in chloroform solution. The resonance
eter using KBr pellets and nuclear magnetic reso- signals for protons were assigned with alphabets are
nance spectroscopy using Joel EX-400 FT-NMR shown in the figure, all the protons in the monomers
spectrometer in CDCl3 with TMS as an internal were accounted well with corresponding signals in the
1
standard for both H-NMR and 13C-NMR spectra. spectrum and are in accordance with targeted struc-

84
T Palani et al.
Scheme 1. Synthesis of polymer Ia–Ic and IIa–IIc.
tures. After polymerization, characteristic absorption and 55⋅8ppm respectively and retained chemical shift
band at 1634cm−1 in FT-IR spectra corresponding to values in the original position after polymerization. In
methacrylate double bond of monomer was completely addition, other chemical shifts representing the mono-
disappeared. Similarly, chemical shift at 5⋅54ppm and mers were broadened in polymers confirmed the
6⋅10ppm assigned to vinyl proton of each monomer monomeric units completely involved in the polymer-
vanished after polymerization in their 1H-NMR spectra ization reactions.
(representative 1H-NMR of polymers is given in
figure 2). At the same time, an additional chemical 3.2 Thermal property
1
shift of −CH2− was observed at 0⋅98ppm in H-NMR
spectra of all the polymers. The chemical shift at Thermal stability of polymers was examined using
125⋅3ppm in 13C-NMR spectrum corresponding to TGA with respect to substituent on the terminal
vinyl carbon is shifted to aliphatic region in the position and spacer length between mesogen and the
polymers. Methylene carbon adjacent to ether and back bone. They displayed 5% weight loss (Td) in
ester linkage in the monomers resonated at 68⋅4ppm nitrogen around 290–311°C and 50% weight loss
Table 1. TGA data polymers Ia–Ib and IIa–IIc.
Mn
Polymer
PDI
n
Weight loss
corresponding (°C)
Total weight loss Char yield
at 600°C
at 600°C
5%
50%
Ia
Ib
Ic
IIa
IIb
IIc
64,165 1⋅11
58,856 1⋅21
61,674 1⋅09 10 310
62,856 1⋅15
65,458 1⋅16
63,124 1⋅15 10 290
6
8
325
320
450
428
415
440
420
405
78
22
20
17
21
19
18
80
83
79
81
82
6
8
318
305

Pendant triazole ring assisted mesogen
85
c
d
g
O
j
k
l
O
i
h
a b
c e
f
N
O
N
N
C
O
O
4
O
c
Figure 1. 1H-NMR spectrum of monomer iia in CDCl3.
observed beyond 405°C indicating their good thermal The polymers were decomposed through single
stability. The TGA traces of polymers Ia–Ic and IIa–IIc stage decomposition phenomenon. On comparing our
are shown in figures 3 and 4 respectively and their data previous report,28 the triazole ring on the terminal
are given in table 1.
position of polymethacrylate systems cleaves around
b
OCH3
d
g
h
i
O
f
e
c
a b
N
O
N
a
a
N
C
O
O
4
O
Figure 2. 1H-NMR spectrum of polymer Ia in CDCl3.

86
T Palani et al.
Figure 3. TGA thermograms of polymers Ia–Ic.
306°C, which is almost similar to the cleavage of ester
linkages present in mesogen of the polymers, accord-
ingly, these polymers demonstrated single stage decom-
position. The methoxy substituted polymers (Ia–Ic)
were stable in the range of 290–299°C and ethoxy
substituted polymers (IIa–IIc) were stable in the range
of 300–311°C. The thermal stability data in table 1
revealed that thermal stability decreased with increas-
ing methylene chain length from 6 to 10 attributed the
presence of ether linkage and methylene chains in the
spacer were expected to introduce greater flexibility
and consequently brought down thermal stability.29
Among the methoxy and ethoxy substituents contain-
ing polymers, ethoxy-based polymers were less stable
than that of methoxy-based polymers (table 1). This
may be explained based on Baeyer’s strain theory, heat
of combustion per −CH2− unit of methoxy are higher
than that of ethoxy30 moiety. Decomposition of
polymers was almost completed around 600°C, after
that no weight loss was observed. Char yield of
Figure 5. DSC thermograms of polymers Ia–Ic.
Figure 4. TGA thermograms of polymers IIa–IIc.
Figure 6. DSC thermograms of polymers IIa–IIc.

Pendant triazole ring assisted mesogen
87
Table 2. DSC and POM data of polymers Ia–Ib and IIa–IIc.
Polymers
n
Tg (°C)
DSC (°C)
Ti
HOPM (°C)
Ti
Tm
ΔT
Tm
ΔT
Ia
Ib
Ic
IIa
IIb
IIc
ia
ib
ic
iia
iib
iic
6
8
10
6
8
10
6
8
10
6
8
10
−
75
68
85
81
78
−
−
−
−
−
212
210
209
220
215
215
121
118
110
113
108
95
251
262
267
271
274
277
147
151
148
138
145
138
42
49
52
51
47
47
26
33
38
25
37
43
208
212
216
218
226
230
124
119
115
114
108
97
253
264
266
271
277
279
146
149
153
141
147
136
45
52
50
53
51
49
22
30
38
27
39
39
−
polymers was measured at 800°C to explore fire crystalline phases.25 DSC experiments were conducted
retardant property of these polymers. It revealed that during second heating at 5°C/min scanning rate and
char yield increased with decreasing spacer length thermograms of Ia–Ic and IIa–IIc series of polymers are
(hexamethylene > octamethylene > decamethylene).
traced in figures 5 and 6 respectively. They exhibited
two endothermic transitions between 96 and 233°C. The
low temperature one is due to crystalline-liquid crystal-
line (Tm) and high temperature one is liquid crystalline-
3.3 Mesomorphic property
The methoxy and ethoxy linked click chemistry assisted isotropic (Ti) transitions. Phase transition temperatures
triazole ring containing mesogens displayed liquid of polymers are tabulated in table 2.
Figure 7. POM photographs of polymers Ib, Ic, IIb and IIc.

88
T Palani et al.
mesogen containing low molecular weight liquid
crystalline compounds displayed smectic-A phases,
which was unable to show the same in polymers
ascribed to the mesogen in the side-chain polymeric
system is more favourable for nematic character than
the smectic nature. The representative DSC thermo-
grams and POM images for monomers ia–ic and iia–
iic are given in figures 8 and 9, respectively and the
transition temperatures are given in table 2. The
polar–polar interaction between triazole rings in low
molecular weight compounds is restricted in poly-
meric system leads to nematic like character than
smectic textures which has advantages for commercial
applications.
4. Conclusion
The click chemistry assisted triazole ring on the terminal
position containing mesogens exhibited liquid crystalline
phases. To investigate the same mesogen in the side chain
polymethacrylate systems, we synthesized two series of
side chain liquid crystalline polymers by free radical
polymerization technique. The mesogen was linked to
backbone through the various spacer units. All the
Figure 8. DSC thermograms of monomers ia and iia.
In addition to these two endothermic transitions,
except Ia, remaining polymers exhibited one small
hump just below the low temperature endothermic
transition corresponding to glass transition (Tg) phe-
nomena. The Tg value indicated in table 2 revealed
that Tg decreases with increasing spacer length
attributed to increase in spacer length could enhance
segmental mobility to decrease Tg. A broad first order
peak is observed for melting transition and indicated a
large amount of energy is involved, where as isotropic
transition consumes relatively less amount of energy
confirmed liquid crystalline phase formation of poly-
mers. The Tm of polymers was in between 209 and
215°C and isotropic transition (Ti) is in between 251
and 277°C. Liquid crystalline phase was observed in
between the Tm and Ti (ΔT = Ti–Tm). The ΔT values
revealed the broad mesophase for the polymers. DSC
analysis disclosed Tm of polymers were decreased
with increasing spacer length from 6 to 10.
ib
iic
The polymers samples were analysed from their
isotropic liquid in the POM for their mesomorphic
property. On cooling from the isotropic liquid, they
exhibited a uniform grainy like texture. Representative
POM photographs Ib, Ic, IIa and IIc are shown in
figure 7 and the phase transition temperatures observed
in POM are summarized in table 2.
The phase transition temperatures noticed from the
POM is in agreement with DSC data. Albeit, this Figure 9. POM photographs of monomer ib and iic.

Pendant triazole ring assisted mesogen
89
monomers and polymers were characterized by FT-IR, 1H
and 13C-NMR spectral techniques. Thermal stability of
polymers was confirmed by thermogravimetric analysis
and revealed that thermal stability decreased with
increasing methylene chain length from 6 to10. Between
the two series of polymers, ethoxy-based polymers were
less stable than that of methoxy-based polymers. The
mesomorphic property and phase transition temperature
of polymers were investigated by differential scanning
colorimetric and polarized optical microscopy wherein,
DSC analysis revealed that Tm of polymers were
decreased with increasing spacer length from 6 to 10.
At the same time, Tg also decreases with increasing
spacer length due to enhancement in segmental mobility
of spacer units. All the polymers exhibited grainy
textures attributed to polar–polar interaction between
triazole rings in the low molecular weight compounds is
highly restricted than that of polymeric system which
leads to formation of nematic textures.
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This research work was financially supported by
University Grants Commission (UGC), New Delhi,
Government of India [F. 31-110/2005 (SR)] and
gratefully acknowledged.
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