Side-chain liquid-crystalline polymer tetrazoles: Synthesis and characterization

Article abstract of DOI:10.5935/0103-5053.20140107

The synthesis and phase behavior of three new side-chain liquid crystal polymers with short and long flexible alkyl spacers are described. These new materials show smectic C (SmC) mesophase. X-ray analysis for two samples has revealed that SmC mesophase displays partial interdigitation for the polymer with short flexible spacer, while for long flexible spacer polymer no interdigitation was observed. ?2014 Sociedade Brasileira de Qui?mica.

Full text of DOI:10.5935/0103-5053.20140107

http://dx.doi.org/10.5935/0103-5053.20140107
J. Braz. Chem. Soc., Vol. 25, No. 7, 1275-1282, 2014.
Printed in Brazil - ©2014 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Article
A
Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
Muhammad Tariq,a,b Shahid Hameed,*,b Rachel F. Magnago,c Ivan H. Bechtoldd and Aloir A. Merlo*,a
aInstituto de Química, Universidade Federal do Rio Grande do Sul (UFRGS),
Av. Bento Gonçalves, 9500, Bairro Agronomia, 91501-970 Porto Alegre-RS, Brazil
bDepartment of Chemistry, Quaid-i-Azam University, 45320 Islamabad, Pakistan
cUnidade Tecnológica, Universidade do Sul de Santa Catarina (Unisul),
Av. Pedra Branca, 25, Cidade Universitária, 88137-270 Palhoça-SC, Brazil
dDepartamento de Física, Universidade Federal de Santa Catarina (UFSC),
Bairro Trindade, 88040-900 Florianópolis-SC, Brazil
A síntese e o comportamento de fase de três novos polímeros cristais líquidos de cadeia lateral
são descritos. Os novos polímeros apresentaram mesofase esmética C (SmC). O estudo de raios X
para duas amostras revelou parcial interdigitação para a mesofase SmC do polímero com espaçador
mais curto, enquanto que com espaçador mais longo o polímero não apresentou interdigitação.
The synthesis and phase behavior of three new side-chain liquid crystal polymers with
short and long flexible alkyl spacers are described. These new materials show smectic C (SmC)
mesophase. X-ray analysis for two samples has revealed that SmC mesophase displays partial
interdigitation for the polymer with short flexible spacer, while for long flexible spacer polymer
no interdigitation was observed.
Keywords: tetrazoles, homopolymer liquid crystals, polyacrylates and SmC mesophase
Introduction
length of the flexible spacer group. Some studies regarding
tetrazole derivatives with LC behavior have recently been
reported in the literature.10-12
The synthesis and studies of the physical properties
of thermotropic liquid crystals are the subjects of current
interest as thermotropic liquid crystals have technological
applications in electro-optic devices.1,2 From the viewpoint of
the science basics, this interest is evident by numerous studies
of both low- and high-molecular weight liquid crystals3-9
indicating the structural dependence of liquid-crystalline
properties. However, the relationship between structural
aspects and mesophase behavior is not well understood.
Liquid crystals (LCs) are systems that can self-organize
due to mesogenic groups that exhibit cooperative
interactions among them. This is the origin of interesting
properties of liquid crystals and extends to both types
of high-molecular weight liquid crystals, i.e., side- and
main-chain liquid crystalline polymers (SCLCP and
MCLCP, respectively). It is well known that the nature
of mesophases depends on the relationship established
between polymer backbone, mesogenic core and the
In order to investigate the correlation between flexible
spacer length, molecular weight and the influence of
tetrazole ring we have synthesized three polymer LCs
containing N-alkylated tetrazole ring as part of mesogenic
core connected to the polyacrylate backbone through
flexible spacer with four and eleven carbon atoms. The
tetrazole ring was built by 1,3-dipolar addition of azide
anion (N3–) to an arylnitrile and regioselectively alkylation
at position 2. The regioselectivity during the alkylation
step has been recently established unequivocally by single
crystal X-ray analysis for two final LCs.13
Results and Discussion
Synthesis
The preparation of key intermediate 3 is outlined in
Scheme 1. It was prepared in four steps starting from
cyanophenol 1 using protection-deprotection strategy to
*e-mail: shameed@qau.edu.pk, aloir.merlo@ufrgs.br

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Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
J. Braz. Chem. Soc.
prevent O-alkylation reaction. The tetrazole heterocycle
was constructed by [3+2] 1,3-dipolar cycloaddition of
azide anion to cyanophenol 1 followed by acetylation
of phenol functionality to yield 2 in 51% yield over two
steps. The alkylation of 2 with nonylbromide yielded the
corresponding N-2 nonyl tetrazolylacetate, which was
subsequently hydrolyzed in basic solution to furnish the
free phenol 3 in 87% yield.
The synthesis of acids 6and 8carrying the polymerizable
acrylate group is outlined in Scheme 2 and 3, respectively.
The acrylate group was introduced using a large excess
of acrylic acid in presence of p-toluene sulfonic acid
(pTSA) and hydroquinone.14 The former was prepared
according to a method described by Portugal et al..15 The
only modification made in this method was in the first
step, when 4-chlorobutyl acetate was employed instead of
4-bromobutyl acetate. 4-Chlorobutyl acetate was obtained
from ring opening reaction of tetrahydrofuran (THF) with
acetylchloride and catalytic amount of zinc chloride as
outlined in Scheme 2.
The intermediate 814 was prepared in three steps as
depicted in Scheme 3. The flexible spacer has eleven
methylene carbon atoms and the polymerizable acrylate
group was introduced in the same way as described for
compound 6. The target acrylates 6 and 8 were isolated and
purified by recrystallization from isopropanol or aqueous
ethanol.
Monomers 9 and 10 were prepared from
4-[(4-propenoyloxy)butyloxy]benzoic acid 6 and
4-[(4-propenoyloxy)undecyloxy]benzoic acid 8,
respectively, by reacting with tetrazolylphenol 3
using dicyclohexyl carbodiimide (DCC) in pyridine
solution and pTSA as a catalyst.15 The yields after
purification were in range of 30-60%. The monomers were
subjected to free radical polymerization in toluene using
2,2’-azobisisobutyronitrile (AIBN) as radical initiator to
give homopolymers 11 and 12 (Scheme 4). The polymers
were purified by successive precipitation with a solution of
dichloromethane in cold methanol. Finally, the amorphous
solid was washed several times with cold ethyl acetate until
Scheme 1. Synthesis of N-2 nonyltetrazolylphenol 3.
Scheme 2. Reaction conditions: (a)AcOCl, ZnCl2 (cat); (b) KOH, p-HOPhCO2Me, N,N-dimethyl formamide (DMF)/benzene (85%); (c) (i) KOH, ethanol/
water; (ii) HCl, H2O (90%); (d) CH2=CHCO2H, pTSA, hydroquinone, CHCl3 (75%).
Scheme 3. Synthesis of polymerizable acrylate 8.

Vol. 25, No. 7, 2014
Tariq et al.
1277
no signal for ethylenic protons was observed in nuclear
magnetic resonance (NMR) analysis. The comparative data
of the homopolymers 11a,b and 12 are shown in Table 1.
in this study have four and eleven methylene carbon atoms.
The polymer backbone for 11a and 11b are closer to the
mesogenic core while in 12 it is relatively away from the
mesogenic core. However, the mesomorphic behavior does
not drastically change with lengthening of the flexible
spacer. Even the variation of the DP was not enough to
change the nature of the mesophase or to significantly alter
the mesophase range as is evident form the comparison
of DP for 11a and 11b, where the first is almost twice as
heavier as the second. Previously reported results have
revealed that when the mesogenic core is derived from
1,4-phenylene unit, the mesophase is nematic in the case
of a short flexible spacer and smectic A phase for long
flexible spacer.17 Considering the polymeric nature of 11a,b
and 12 and that they do not tend to crystallize on cooling
a mesophase fixation when the samples were exposed to
polymerization action. From POM analysis, both polymers
show a glassy appearance. The glass transition temperature
tends to decrease as the molecular weight decreases for
polymers with the same flexible spacer, compare 11a and
11b. The Tg tends to be higher for a polymer that has
longer flexible spacer as observed for 12. In general, a
lower polymer glass transition temperature implies that
the backbone is more flexible.
Liquid-crystalline properties
The mesomorphic properties of the polymers were
studied using polarizing optical microscopy (POM) and
differential scanning calorimetry (DSC). The texture of
the mesophase16 was identified by microscopic studies
on cooling from the isotropic to mesomorphic state. The
liquid-crystalline properties of the polymers 11a,b and
12 are compiled in Table 1. Table 1 lists the observed
layer spacing obtained from the Bragg equation and the
calculated length of the monomer molecule obtained from
the program ChemBio3D Ultra.
The synthesis of polyacrylate 11a was carried out
using 3 wt.% of AIBN while polymerization reaction to
give 11b and 12 were performed using 5 wt.% of AIBN.
The molecular weight (Mn) and degree of polymerization
(DP) for 11a is twice than 11b and 12, probably related to
the content of initiator during the chemical polymerization
process. Polymers 11b and 12 may be considered as
oligomers considering the low value of DP for these
polymers. All the polymers exhibited a glass transition
temperature (Tg) and enantiotropic SmC phase. For
instance, polymer 12 shows Tg at 70.5 °C and enters the
smectic C phase with a range of 36.5 °C for the mesophase
and goes to isotropic phase at 107 °C. The flexible spacers
Data compiled in Table 1 shows that the shortening or
lengthening of flexible spacer does not have any influence on
the nature of the mesophase. However, as will be discussed
in the X-ray section, the structure of SmC phase is dependent
on the length of flexible spacer. Smectic C phase observed
Scheme 4. Synthesis of polymers 11 and 12.
Table 1. Data for polymers 11a,b and 12: GPC, transition temperature and X-ray diffraction
Transition
Observed layer
Calc. layer
entry
Mn
Mw/Mn
DP
Yield / %
temperaturesa / °C
g 70 SmC 129 I
g 54 SmC 130 I
g 71 SmC 107 I
spacing (l) / Åb
spacing (d) / Åc
11a
11b
12
7460
4420
4520
1.2
1.2
1.3
14
8
69
85
78
–
–
45.2:23.8:16.1
36.6
32.8
40.4
7
aTransition temperatures were acquired upon heating by POM; bdata collected at 90 °C; cdata collected at 80 °C. Mn: g mol-1; DP: number average degrees
of polymerization; GPC: gel permeation chromatography.

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Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
J. Braz. Chem. Soc.
in this study probably is the result of folded-shape of the
mesogenic core having a non-symmetrical tetrazole ring.
The folded-shape of mesogenic core prints on the polymer
material its structural feature, which overcomes the tendency
of the main-chain to adopt a random coil conformation.18
The mesomorphic behavior of compounds 11a,b and 12
was investigated between crossed polarizers using optical
microscopy. Figure 1a displays the normal texture for 11a,b
and 12. Schieliren texture is barely seen in this picture due
to the nature of the sample and the thickness. However,
in other areas where the thickness is smaller, especially
in the border zone of the samples, the Schlieren texture
flourishes radiantly (Figure 1b). The Schlieren texture with
four-point brushes characteristic of smectic C phase is seen
for 11b (Figure 1b). The assignment to nematic phase was
discarded considering that from isotropic phase no droplets
were observed upon cooling.Also, the absence of optically
extinct homeotropic and flashing areas on the mechanical
disturbance corroborates to eliminate the nematic phase.
80 °C, respectively. In both cases the spectrum contains
a sharp peak in the low-angle region corresponding to
the Miller index (001), where by applying Bragg’s law
resulted in an interlayer spacing of 45.2 0.1 Å for 11b
and 36.6 0.1 Å for 12. In addition, a broad diffuse
band centered around 4.4 Å is present, which is related
to the short-range correlations between neighboring
mesogenic molecules inside the layers. Compound 11b
also displayed secondary order peaks (002) and (003)
corresponding to distances of 23.8 0.1 and 16.1 0.1Å,
respectively, following the relation 1:2:3 with respect to
(001), as expected for smectic phases. However, only
the (001) is observed for compound 12, which indicates
that the smectic order is short range correlated. The
molecular length of the monomer molecules 9 and 10
was calculated with the program ChemBio3D Ultra
considering the most extended configuration, giving
32.8 0.1 and 40.4 0.1 Å, respectively. One can see
that the calculated value for monomer 10 is around 3.8 Å
larger than the interlayer distance measured for polymer
12, which is consistent with conformational disorder of
the aliphatic chains and inclination of the molecules inside
the layers expected for the SmC phase. On the other hand,
monomer 9 is around 12.4 Å shorter than the interlayer
distance measured for polymer 11b. The ratio between the
interlayer distance and the molecular length is 1.38 and
this observation is consistent with a partial interdigitation
of the mesogens inside the layers.
X-Ray diffraction studies
X-Ray diffraction (XRD) studies were carried out
to confirm the POM results and obtain more detailed
information on the structures and types of liquid crystalline
phases. Generally, a diffuse broad peak where 2q assumes
values from 16 to 22° in the wide angle region of X-ray
diffraction curves can be observed for polymers but not
for polymer LCs with smectic, nematic, and N* phase
structures due to the average distance between the
mesogenic groups. Sharp and strong peaks at low angles
in which 2q assumes values from 1 to 5° can be observed
for a normal smectic structure which exhibits a layered
packing arrangement, but not for N* and nematic structures.
Figure 2 shows the patterns of compounds 11b and 12
to investigate the structure of their smectic phases at 90 and
If we consider that the backbone is confined by the
smectic field and lies between the layers,19 two arrangements
for polymers 11b and 12 are possible. In one arrangement,
the side chains are closer to the backbone than in the other,
causing a partially interdigitated SmC phase. In the other
arrangement, the side chains exhibit no interdigitation. In
both cases, the motion of the backbone is constrained by
the orientational and positional order of the smectic layer.
Figure 1. Schlieren texture observed for polymer 11a at room temperature (a) and 11b at 10 °C (b).

Vol. 25, No. 7, 2014
Tariq et al.
1279
Conclusions
In summary, we have synthesized three homopolymers
having the tetrazole ring as the key structural brick for
the mesomorphic phenomenon. They showed smectic
C enantiotropic behavior with a large mesophase range.
Flexibility of polymer backbone, Tg and Tc transition
temperatures are dependent on the polymerization degree.
These are important parameters to be considered in the
design and synthesis of new materials. X-Ray analysis
showed a partial interdigitation of the mesogens inside the
layers of the polymer with short flexible spacer.
Experimental
Characterization
1H and 13C NMR spectra were recorded on a Bruker
AC-300F spectrometer in CDCl3, using tetramethylsilane
(TMS) as the internal standard. Infrared (IR) spectra were
recorded on a Perkin-Elmer 781 spectrometer in KBr disc or
film. The thermal transitions and the mesomorphic textures
of the compounds were observed by optical microscopy
using a Leitz Ortholux polarizing microscope in conjunction
with a Mettler FP 52 heating stage. The XRD experiments
were carried out using X’PERT-PRO (PANalytical)
diffractometer using the linear monochromatic Cu Kα
radiation (λ = 1.5418 Å) and applied power of 1.2 kVA.
The samples consisted of an amount of powder on a
glass plate placed in the diffractometer chamber on the
TCU2000 temperature control unit (Anton Paar), allowing
temperature control during the measurement. The scans
were performed in continuous mode from 2 to 30° (2q
angle) with the samples in the mesophase, obtained by
cooling from the isotropic state.
Figure 2. (Top) X-Ray diffraction patterns for compound 11b (black line)
and 12 (gray line), with indication of the Miller indices. SmC phase at 90
and 80 ºC for 11b and 12, respectively. (Bottom) Two types of smectic
C structure exhibited by side-chain liquid crystal polymers 11b and 12.
The evidence for this classification comes from other data
published in the literature.20 From Table 1, the higher glass
transition temperature is observed for 12, which exhibits
no interdigitated smectic phase. The side chains are more
decoupled from the polymer backbone due to the longer
flexible spacer. The anisotropic cores have more freedom
to arrange themselves in an appropriate manner with more
independence from the main chain orientation of backbone.
For polymer 11b, with smaller flexible spacer, the behavior
is similar to the nematic one. In this sense, it is possible
to expect some interdigitation of the laterally anisotropic
core. These structural features of the smectic phase have
pronounced effects on packing density as well as transition
properties. Mesophase structure that possesses a more
compactness degree has a less specific free volume.21 The
closer the mesogenic cores to the random coil conformation
of polymer, the higher the influence of polymer backbone on
the final structure of the mesophase. The main chain was no
longer a random coil. A considerable degree of mesogenic
order is transferred to the main chain by the flexible
spacer.18,22 The behavior of 11b is in accordance with the
general tendency that the increasing backbone flexibility for a
given spacer length and mesogenic core tends to diminish the
glass transition temperature while increasing the temperature
of clearing (Tc) or the clearing point.2,15,23
Synthesis
All reagents were purchased from Aldrich Chemical
Company (USA) and solvents were used as received from
Merck. The synthesis of the title compounds were carried
out according to standard methods outlined in Schemes
1, 2, 3 and 4.
4-(2H-Tetrazol-5-yl)phenyl acetate (2)
(i) 4-(2H-Tetrazol-5-yl)phenol: To a solution of
4-cyanophenol (1) (5.0 g, 0.042 mol) in 28 mL N,N-
dimethyl formamide (DMF) was added sodium azide
(11.0 g, 0.17 mol) and ammonium chloride (9.0 g,
0.17 mol). The mixture was stirred for 24 h maintaining
the temperature at 120 °C. The reaction mixture was

1280
Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
J. Braz. Chem. Soc.
cooled to room temperature and was poured into 50 mL
of ice cold water. The mixture was acidified with
concentrated HCl to pH 2. The precipitate formed was
filtered off and the product was recrystallized from
ethanol giving orange crystals.Yield 68%; m.p. 241.8 oC;
Rf = 0.23 (n-hexane:ethyl acetate; 6:4); IR (KBr)
precipitated solid was filtered and purified by crystallization
from ethanol.Yield 87%; white solid; m.p. 70 °C; Rf = 0.72
(n-hexane:ethyl acetate; 7:3); IR (KBr) nmax/cm-1 3163,
1
2924, 1613, 845; H NMR (CDCl3, 300 MHz) d 0.9 (t,
3H, J 6.9 Hz, CH3), 1.4-1.3 (m, 12H, (CH2)6), 2.1 (m, 2H,
CH2CH2N), 4.6 (t, 2H, J 7.2 Hz, NCH2), 6.9 (d, 2H, J 8.8
Hz, Ar–H), 8.0 (d, 2H, J 8.8 Hz, Ar–H); 13C NMR (CDCl3,
75 MHz) d 14.1, 22.6, 26.4, 28.9, 29.2, 29.3, 29.4, 31.8,
53.2, 115.9, 119.7, 128.5, 157.9, 164.9.
n
max/cm-1 3445, 3254, 2930, 2845, 1608; 1H NMR (CDCl3,
300 MHz) d 4.65 (s broad, 1H, NH); 7.3 (d, 2H, J 6.6 Hz,
Ar–H); 8.1 (d, 2H, J 6.6 Hz, Ar–H); 10.3 (s broad, 1H,
OH); 13C NMR (CDCl3, 75 MHz) d 122.6, 125.5, 127.3,
152.2, 169.4.
4-Chlorobutyl acetate (5): To a solution of
tetrahydrofuran (25.2 g, 0.35 mol) and zinc chloride
(20 mg) at 0 °C was added dropwise acetyl chloride (23.5
g, 0.30 mol) and the solution was stirred for 40 min at this
temperature followed by 30 min at room temperature and
refluxed for 4 h more. The reaction mixture was dissolved
in diethyl ether (200 mL) and the organic phase was
washed with NaHCO3 5% (100 mL), water (100 mL),
NaCl solution (100 mL) and again water (100 mL). The
organic phase was dried over anhydrous sodium sulfate
and distilled. Yield 71%; b.p. 95 °C at 24 mmHg (b.p.
92 °C at 22 mmHg)24; IR (KBr) nmax/cm-1 2960, 1735,
(ii) 4-(2H-Tetrazol-5-yl)phenyl acetate (2): To a
3 mol L-1 sodium hydroxide solution (27.6 mL) was added
4-(2H-tetrazol-5-yl)phenol (5.4 g, 0.03 mol). The mixture
was cooled in an ice bath followed by dropwise addition
of acetic anhydride (7.9 mL, 0.084 mol) along with some
ice. The reaction mixture was vigorously stirred for 30 min
and the precipitate formed was filtered off, washed with
cold water and recrystallized from water-methanol. Yield
58%; white solid; m.p. 182 oC; Rf = 0.33 (n-hexane:ethyl
acetate; 6:4); IR (KBr) nmax/cm-1 3075, 2938, 2844, 1758,
1613, 1200; 1H NMR (CDCl3, 300 MHz) d 2.3 (s, 3H, CH3),
6.2 (s, broad, 1H, NH), 7.4 (d, 2H, J 6.6 Hz, Ar–H), 8.1 (d,
2H, J 6.6 Hz, Ar–H); 13C NMR (CDCl3, 75 MHz) d 22.9,
122.4, 125.2, 128.0, 153.0, 158.0, 169.0.
1
1340, 1250, 1070, 930, 725, 650; H NMR (CDCl3,
300 MHz) d 1.6 (m, 4H, (CH2)2), 1.8 (s, 3H, CH3), 3.4
(m, 2H, CH2Cl), 3.9 (t, 2H, J 6.3 Hz, CH2O).
4-(2-Nonyl-2H-tetrazol-5-yl)phenol (3)
4-[(4-Propenoyloxy)butyloxy]benzoic acid (6):25 In a
Dean-Stark apparatus were added 4-(w-hydroxybutoxy)
benzoic acid (7.7 g, 0.037 mol), acrylic acid (23.0 g,
0.324 mol) chloroform (150 mL), pTSA (1.5 g, 0.008 mol)
and hydroquinone (1.5 g, 0.014 mol). The mixture was
refluxed until the end of the reaction. After a standard
workup procedure the product was recrystallized
from isopropanol. Yield 65%; m.p. 120 °C; IR (KBr)
(i ) 4-(2-Nonyl-2H-tetrazol-5-yl)phenyl acetate: A
mixture of 4-(2H-tetrazol-5-yl)phenyl acetate (2) (2.50 g,
0.012 mol), nonylchloride (1.95 g, 0.012 mol) and
anhydrous potassium carbonate (1.65 g, 0.012 mol) in
30 mL acetone was heated under reflux for 48 h. The
reaction mixture was cooled to room temperature and
filtered. The solvent was removed at low pressure and the
product was recrystallized from ethanol. Yield 51%; m.p.
n
max/cm-1 2940 (broad), 1750, 1680, 1580, 1260, 1080, 930;
o
53-54 C; white solid; Rf = 0.74 (n-hexane:ethyl acetate;
1H NMR (CDCl3, 300 MHz) d 1.8 (m, 4H, CH2), 4.1 (m,
7:3); IR (KBr) nmax/cm-1 2916, 2859, 1751, 1215, 1613,
918; 1H NMR (CDCl3, 300 MHz) d 0.8 (t, 3H, J 6.9 Hz,
CH3), 1.2-1.5 (m, 12H, (CH2)6), 2.1 (m, 2H, CH2CH2N),
2.3 (s, 3H, CH3), 4.6 (t, 2H, J 7.2 Hz, NCH2), 6.9 (d, 2H,
J 8.8 Hz, Ar–H), 8.0 (d, 2H, J 8.8 Hz, Ar–H); 13C NMR
(CDCl3, 75 MHz) d 14.1, 21.2, 22.6, 26.4, 28.9, 29.2, 29.3,
29.4, 31.8, 53.3, 122.2, 125.3, 128.1, 152.1, 164.3, 169.2.
(ii) 4-(2-Nonyl-2H-tetrazol-5-yl)phenol (3): The
4-(2-Nonyl-2H-tetrazol-5-yl)phenyl acetate (1.023 g,
3.1 mmol) was added to 20 mL methanol followed by
addition of potassium hydroxide (1.17 g, 3.1 mmol) in 5 mL
of water and refluxed for 12 h. The mixture was cooled to
room temperature, filtered off and was concentrated on
a rotary evaporator. The mixture was poured onto 100 g
of ice and acidified with concentrated HCl to pH 2. The
2H, CH2O), 4.2 (s, 2H, CH2O), 5.8 (dd, 1H, Jgem 1.8 Hz,
2
3Jcis 10.8 Hz, CH=CH2), 6.1 (dd, 1H, Jcis 10.2 Hz,
3
3Jtrans 17.1 Hz, CH=CH2), 6.4 (dd, 1H, Jgem 1.5 Hz,
2
3Jtrans 17.4 Hz, CH=CH2), 6.8 (d, 2H, J 8.0 Hz, Ar–H), 8.0
(d, 2H, J 8.0 Hz, Ar–H).
4-[(4-Propenoyloxy)undecyloxy]benzoic acid (8):
Compound 8 was synthesized according to reference 14 and
Ritter et al..26 Yield 85%; white solid; m.p. 94 ºC; IR (KBr)
n
max/cm-1 3080-2700, 2929, 2853, 1718, 1685, 1605, 1464,
1250, 1177, 1037, 854, 772; 1H NMR (CDCl3, 300 MHz)
d 1.3 (m, 14H, (CH2)7), 1.7 (m, 4H, (CH2)2), 4.1 (m, 4H,
CH2O), 5.8 (m, 1H, CH=CH2), 6.1 (m, 1H, CH=CH2), 6.4
(m, 1H, CH=CH2), 6.9 (d, 2H, J 9.0 Hz, Ar–H), 8.0 (d, 2H,
J 8.8 Hz, Ar–H).

Vol. 25, No. 7, 2014
Tariq et al.
1281
Monomers 9 and 10: General procedure. Acids 6 or
8 (0.005 mol), 4-(2-nonyl)-2H-tetrazol-5-ylphenol (3)
(0.0055 mol), DCC (0.006 mol) and pTSA (0.0026 mol)
were dissolved in freshly distilled pyridine (5 mL). The
reaction was stirred for 3 days at room temperature.
The mixture was filtered and washed with chloroform.
The organic phase was washed with 10% cold aqueous
hydrochloric acid (100 mL) and water and dried over sodium
sulfate. The solvent was removed in a rotatory evaporator
and the crude solid was purified by recrystallization from
methanol.
several times with ethyl acetate to separate the unreacted
monomer, which left behind pure polymers 11a,b and 12.
Poly-{4-(2-nonyl-2H-tetrazol-5-yl)phenyl
4-[(propionyloxy)butyloxy)]}benzoate (11a,b): Yields 69%
for 11a and 85% for 11b; white solid; IR (neat) nmax/cm-1
1
2935, 2856, 1720, 1611, 1250, 765; H NMR (CDCl3,
300 MHz) d 0.9 (m, 3H, CH3), 1.2-2.0 (m, 18H, m), 4.0-4.2
(m, 4H, CH2O), 4.6 (m, 2H, CH2N), 6.9 (m, 2H, Ar–H),
7.3 (m, 2H, Ar–H), 8.1 (m, 2H, Ar–H), 8.2 (m, 2H, Ar–H);
13C NMR (CDCl3, 75 MHz) d 14.2, 21.1-29.4, 31.8, 53.3,
64.4, 67.6, 114.3, 121.6, 122.3, 125.2, 128.0, 132.4, 152.5,
163.6, 164.4, 164.5, 171.1.
4-(2-Nonyl-2H-tetrazol-5-yl)phenyl 4-[(propionyloxy)
butyloxy)]benzoate (9): Yield 54%; white solid; m.p.
67-68 oC; Rf = 0.74 (n-hexane: ethyl acetate; 7:3); IR (KBr)
Poly-{4-(2-nonyl-2H-tetrazol-5-yl)phenyl 4-[(propionyloxy)
1
n
max/cm-1 2935, 2856, 1720, 1611, 1250, 765; H NMR
undecyloxy)]}benzoate (12):Yield 78%; white solid; IR (neat)
n
max/cm-1 2919, 2849, 2355, 1720, 1611, 1258, 765; 1H NMR
(CDCl3, 300 MHz) d 0.8 (t, 3H, J 6.0 Hz, CH3), 1.3-2.5 (m,
18H, (CH2)9), 4.0-4.3 (m, 4H, CH2O), 4.6 (t, 2H, J 7.2 Hz,
CH2N), 5.8 (dd, 1H, 3Jcis 10.2 Hz, 2Jgem 1.6 Hz, CH=CH2),
(CDCl3, 300 MHz) d 0.8 (t, 3H, J 6.9 Hz, CH3), 1.2-2.0
(m, 32H), 4.0-4.1 (m, 4H), 4.6 (m, 2H, CH2O), 6.9 (m, 2H,
Ar–H), 7.3 (m, 2H, Ar–H), 8.1 (m, 2H, Ar–H), 8.2 (m, 2H,
Ar–H); 13C NMR (CDCl3, 75 MHz) d 14.2, 21.1-29.4, 31.8,
31.8, 53.2, 64.5, 68.3, 114.3, 121.3, 122.3, 125.1, 128.0,
132.3, 152.6, 163.6, 164.4, 164.6, 171.1.
3
3
6.1 (dd, 1H, Jcis 10.2 Hz, Jtrans 17.3 Hz, CH=CH2), 6.4
(dd, 1H, 3Jtrans 17.3 Hz, 2Jgem 1.7 Hz, CH=CH2), 6.9 (d, 2H,
J 8.0 Hz, Ar–H), 7.3 (d, 2H, J 7.4 Hz, Ar–H), 8.0 (2H, d,
J 8.0 Hz, Ar–H), 8.2 (d, 2H, J 7.3 Hz, Ar–H); 13C NMR
(CDCl3, 75 MHz) d 14.1, 14.2, 21.1-29.4, 31.8, 53.3, 60.4,
64.4, 67.6, 114.3, 121.6, 122.3, 125.2, 128.0, 132.4, 152.5,
163.6, 164.4, 164.5, 171.1.
Supplementary Information
Supplementary data (1H and 13C NMR spectra) are
available free of charge at http://jbcs.sbq.org.br as PDF file.
4-(2-Nonyl-2H-tetrazol-5-yl) phenyl 4-[(propionyloxy)
undecyloxy)]benzoate (10): Yield 35%; white solid; m.p.
73-75 °C; Rf = 0.74 (n-hexane: ethyl acetate; 7:3); IR
(KBr) nmax/cm-1 2919, 2849, 2355, 1720, 1611, 1258, 765;
1H NMR (CDCl3, 300 MHz) d 0.8 (t, 3H, J 6.9 Hz, CH3),
1.3-2.0 (m, 32H, (CH2)16), 4.1 (t, 2H, J 6.5 Hz, CH2O),
4,15 (t, 2H, J 6.8 Hz, CH2O), 4.6 (t, 2H, J 7.2 Hz, CH2N),
5.8 (dd, 1H, 2Jgem 1.5 Hz, 3Jcis 10.4 Hz, CH=CH2), 6.1 (dd,
Acknowledgements
The authors gratefully acknowledge INCT-Catalise,
Fapergs-Edital PqG 2012, Edital 01/12-PPG-Química-
UFRGS and thank LDRX-DF/UFSC for the X-ray
diffraction experiments. We also thank the Higher
Education Commission of Pakistan for their support. M.
Tariq thanks TWAS-CNPq program for financial assistance
for accomplishing this valuable work.
3
3
1H, Jcis 10.4 Hz, Jtrans 17.3 Hz, CH=CH2), 6.4 (dd, 1H,
2Jgem 1.5 Hz, 3Jcis 17.3 Hz, CH=CH2), 6.9 (d, 2H, J 9.0 Hz,
Ar–H), 7.3 (d, 2H, J 8.8 Hz, Ar–H), 8.1 (d, 2H, J 8.9 Hz,
Ar–H), 8.2 (d, 2H, J 8.8 Hz, Ar–H); 13C NMR (CDCl3,
75 MHz) d 14.0, 14.2, 29.6-21.0, 31.8, 53.2, 60.3, 64.5,
68.3, 114.3, 121.3, 122.3, 125.1, 128.0, 132.3, 152.6, 163.6,
164.4, 164.6, 171.1.
References
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the reaction the mixture was poured into cold methanol to
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Submitted: March 27, 2014
Published online: May 20, 2014

J. Braz. Chem. Soc., Vol. 25, No. 7, S1-S6, 2014.
Printed in Brazil - ©2014 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Supplementary Information
SI
Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
Muhammad Tariq,a,b Shahid Hameed,*,b Rachel F. Magnago,c Ivan H. Bechtoldd and Aloir A. Merlo*,a
aInstituto de Química, Universidade Federal do Rio Grande do Sul (UFRGS),
Av. Bento Gonçalves, 9500, Bairro Agronomia, 91501-970 Porto Alegre-RS, Brazil
bDepartment of Chemistry, Quaid-i-Azam University, 45320 Islamabad, Pakistan
cUnidade Tecnológica, Universidade do Sul de Santa Catarina (Unisul),
Av. Pedra Branca, 25, Cidade Universitária, 88137-270 Palhoça-SC, Brazil
dDepartamento de Física, Universidade Federal de Santa Catarina (UFSC),
Bairro Trindade, 88040-900 Florianópolis-SC, Brazil
Figure S1. 1H NMR spectrum (CDCl3, 300 MHz) of 2.
*e-mail: aloir.merlo@ufrgs.br

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Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
J. Braz. Chem. Soc.
Figure S2. 1H NMR spectrum (CDCl3, 300 MHz) of 3 (solvent peak at 3.7 ppm).
Figure S3. 13C NMR spectrum (CDCl3, 75 MHz) of 3.

Vol. 25, No. 7, 2014
Tariq et al.
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Figure S4. 1H NMR spectrum (CDCl3, 300 MHz) of monomer 9 (n = 4).
Figure S5. 13C NMR spectrum (CDCl3, 75 MHz) of monomer 9 (n = 4).

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Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
J. Braz. Chem. Soc.
Figure S6. 1H NMR spectrum (CDCl3, 300 MHz) of monomer 10 (n = 11).
Figure S7. 13C NMR spectrum (CDCl3, 75 MHz) of monomer 10 (n = 11).

Vol. 25, No. 7, 2014
Tariq et al.
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Figure S8. 1H NMR spectrum (CDCl3, 300 MHz) of polymer 11a (n = 4).
Figure S9. 13C NMR spectrum (CDCl3, 75 MHz) of polymer 11a (n = 4).

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Side-Chain Liquid-Crystalline Polymer Tetrazoles: Synthesis and Characterization
J. Braz. Chem. Soc.
Figure S10. 1H NMR spectrum (CDCl3, 300 MHz) of polymer 12 (n = 11).