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E. Hür et al. / Reactive and Functional Polymers 99 (2016) 35–41
higher specific capacitance values, we report the synthesis, electro-
polymerization and electrochemical characterization of a novel 2-
(thiophen-2-yl)-4-(thiophen-2-ylmethylene)oxazol-5(4 H)-one, 3,
monomer on PGE. The synthesis of this new thiophene monomer has
been realized differently from the literature by using benzotriazole
chemistry. Benzotriazole, which is a considerable heterocyclic com-
pound, has advantages (i.e. be stability in many synthesis conditions,
nontoxic, inexpensive and easy to remove at the end of the synthesis
in both acidic and basic media) in the development of new synthesis
methods. Since benzotriazole and its derivatives are UV-active, their
reaction process is visualized easily. On the other hand, most of
benzotriazole derivative has crystalline structure that enables to
examine with chromatographic methods [27]. The monomer, 3, has
been electrochemically polymerized on PGE by using CA technique.
Then, the prepared electrode has been characterized by using SEM,
CV, EIS and RCP techniques. Real supercapacitor performance of the
electrode has been examined by using galvanostatic charge–discharge
in two electrode system.
30 min, a solution of thiophene-2-carboxylic acid (1 eq.) was added.
After 2 h, the solid was filtered and washed with THF (50 mL). The
solvent was removed under vacuum from the combined filtrate. To
the residue, ethyl acetate (50 mL) was added; the mixture was washed
with 20% Na2CO3 (3 × 30 mL). The organic layer was dried over anhy-
drous Na2SO4, then it was filtered and the solvent was evaporated
under vacuum to obtain a solid product, (1 H-benzo[d] [1,2,3]triazol-
1-yl)(thiophen-2-yl)methanone, 1, in 90% yield.
2.2.2. Preparation of 2-(thiophene-5-carboxamido)acetic acid, 2
The solution of (1 H-benzo[d] [1,2,3]triazol-1-yl)(thiophen-2-
yl)methanone, 1, (1 eq.) in dioxane (80 mL) was added to solution of 2-
aminoacetic acid (1 eq.) in distilled water (40 mL) and NaOH (1 eq.).
After 2 h, dioxane was removed under vacuum and the resulted reaction
mixture was washed with ethyl acetate (3 × 30 mL). Collected water
layers were acidified to pH = 2 using 10% HCl solution. This solution
was extracted with ethyl acetate (2 × 30 mL). Collected organic layers
were dried over anhydrous Na2SO4, and the solvent was removed under
vacuum to obtain a solid product 2-(thiophene-5-carboxamido)acetic
acid, 2, in 97% yield.
2. Experimental
2.1. Chemicals and materials
2.2.3. Preparation of 2-(thiophen-2-yl)-4-(thiophen-2-
ylmethylene)oxazol-5(4 H)-one, 3
All chemicals were of reagent-grade purity or better, and used as
obtained from the commercial suppliers. THF was used freshly after
distillation with sodium in the presence of benzophenon. Column chro-
matography was conducted with silica gel 200–425 mesh. NMR spectra
were recorded in CDCl3 with TMS as the internal standard for 1H
(500 MHz) or a solvent as the internal standard for 13C (125 MHz)
using Bruker NMR equipment. All electrochemical experiments except
galvanostatic charge–discharge method were carried out in a conven-
tional three electrode system using PGE as working electrode, platinum
sheet as a counter electrode and pseudo Ag wire as a reference elec-
trode, which all potentials were referenced. PGE is Tombo lead with a
diameter of 0.50 mm. The PGE has been prepared by cutting the leads
into 3 cm long sticks and 2 cm (area 0.31 cm2) was dipped in electrolyte.
A Rotring Tikky pencil model was used as a holder for PGE. Electrical
contact with the PGE was obtained by soldering a metallic wire to the
metallic part of the holder. All electrodes were cleaned in ACN using ul-
trasonic bath (Bandelin Sonarex) and dried before each experiment. The
all electrochemical measurements were carried out using A Gamry 3000
potentiostat/galvanostat/ZRA system and obtained data were analyzed
using Gamry CMS-300 (version 5.50b) framework/analysis software.
All electrochemical experiments were carried out at 25 °C and at open
air atmosphere. Surface morphology was studied using a Zeiss Ultraplus
model field emission scanning electron microscopy (FE-SEM).
2-(thiophene-5-carboxamido)acetic acid (1 eq.), thiophene-2-
carbaldehyde (1 eq.) and sodium acetate (1 eq.) in acetic anhydride
(10 mL) was heated to reflux for 2 h. Then the solvent was evaporated
under vacuum to give the crude product, which was purified by
column chromatography to obtain pure product 2-(thiophen-2-yl)-
4-(thiophen-2-ylmethylene)oxazol-5(4 H)-one, 3, in 93% yield.
2-(thiophen-2-yl)-4-(thiophen-2-ylmethylene)oxazol-5(4H)-one,
3. (93%), yellow microcrystals, 1H NMR (CDCl3, 500 MHz) 7,90 (d, J =
3,08 Hz, 1H), 7,33 (d, J = 5,04 Hz, 1H), 7,70 (d, J = 4,31 Hz, 1H), 7,64
(d, J = 3,62 Hz, 1H), 7,46 (s, 1H), 7,23 (t, J = 4,05 Hz, 1H), 7,18 (t, J =
3,91 Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ 124,1, 128,0, 128,6, 128,7,
130,6, 132,6, 133,1, 134,7, 135,14, 137,7, 158,3, 166,6 ppm.
2.3. Preparation of the electrode
Electrode was prepared by electrochemical polymerization of 2-
(thiophen-2-yl)-4-(thiophen-2-ylmethylene)oxazol-5(4 H)-one, 3, on
PGE using CA technique in ACN solution containing 0.01 M monomer
and 0.10 M TBAP. CA experiments were performed applying a constant
potential of +1.50 V for 240 s. After the electrochemical polymeriza-
tion, PGE/PTTMO was removed from the polymerization medium
and rinsed with ACN to remove monomer molecules and then dried
in air. The mass of the polymer film was measured by weighing using
a precision balance after being held under reduced pressure.
2.2. Synthesis of 2-(thiophen-2-yl)-4-(thiophen-2-ylmethylene)oxazol-
5(4 H)-one, 3
2.4. Electrochemical characterization
2-(thiophen-2-yl)-4-(thiophen-2-ylmethylene)oxazol-5(4 H)-one,
3, was synthesized described method in Scheme 1 [28,29].
Electrochemical performances of PGE and PGE/PTTMO were tested
by using CV, EIS, galvanostatic charge–discharge and RCP techniques
in monomer free solution. CV measurements were employed in the
potential range between −0.20 and +1.90 V at different scan rates
(10, 20, 30, 50 and 75 mV s−1). The specific capacitance of PGE/PTTMO
was calculated at all scan rates from CV measurements using following
2.2.1. Preparation of (1 H-benzo[d][1,2,3]triazol-1-yl)(thiophen-2-
yl)methanone, 1
To a solution of 1 H-benzotriazole (4 eq.) in THF (80 mL), SOCl2
(1 eq.) was added dropwise with stirring at room temperature. After
Scheme 1. Preparation of 2-(thiophen-2-yl)-4-(thiophen-2-ylmethylene)oxazol-5(4 H)-one, 3.