Self-doped N-propansulfonic acid polyaniline-polyethylene terephthalate [603181]

Self-doped N-propansulfonic acid polyaniline-polyethylene terephthalate
film used as active sensor element for humidity or gas detection
Ana-Maria Solonaru ,1Mircea Grigoras,1Iulian Petrila,2Florin Tudorache3
1“P. Poni ”Institute of Macromolecular Chemistry, Electroactive Polymers Department, 41A Gr. Ghica Voda alley, Iasi 700487,
Romania
2Faculty of Automatic Control and Computer Engineering, Gheorghe Asachi Technical University of Iasi, StreetStr. Dimitrie Mangeron,
Nr. 27, Iasi 700050, Romania
3Research Center on Advanced Materials and Technologies, Institute for Interdisciplinary Research —Science Research Department,
“Alexandru Ioan Cuza ”University of Iasi, Iasi 700506, Romania
Correspondence to: A.-M. Solonaru (E-mail: [anonimizat]) and F. Tudorache (E-mail: florin[anonimizat])
ABSTRACT: In this work, we report the fabrication of sensors ’element for humidity or gases, prepared by in situ polymerization of aniline
N-propansulfonic acid using ammonium persulfate in acidic medium. The polymer is being used in the form of powder or deposited in multiple
layers onto the PET film. Various techniques including Fourier Transform infrared (FTIR), ultraviolet- –visible spectroscopy (UV –vis), X-ray dif-
fraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the as-prepared sensing materials. The film has been
tested for humidity in fluence, where the signi ficant variations in electrical characteristics were observed, suggesting its usefulness for humidity
sensors. Also, for different organic and inorganic gases, a relatively low operating temperature and important sensitivity were observed that indi –
cate its applicability as an active element for general gases sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 ,136, 47743.
KEYWORDS: electrical properties; humidity sensor; organic and inorganic gas sensors; PET; poly(aniline-N-propane sulfonic acid)
Received 14 September 2018; accepted 22 February 2019
DOI: 10.1002/app.47743
INTRODUCTION
One of the most serious problems that affect environment stability
and human population is contaminations with different toxic gases,such as carbon monoxide,
1carbon dioxide,2,3ammonia,4acetone,5,6
liquefied petroleum gas,7,8and so on, which provokes respiratory,
sensorial, and cardiovascular disorders, as well as atmospheric
pollution.9–11Hence, precise detection of these gases sensors, as well
as humidity sensors,12is very important, especially for environment,
industry, and people ’sh e a l t h .13–18
A lot of attention is devoted to polyaniline (PANi), one of the most
promising conducting polymers, ca ndidate for application of gas and
humidity sensing, due to its properties such as unique conductivityand chemical stability in the environment.
14,19 –26However, the PANi
is intractable, infusible, and insol uble, and these inconveniences ham-
per greatly the processing and a pplications of the polymer.27,28There-
fore, much effort has been made to improve the major drawbacks, likelack of processability and solubility of the conducting PANi and manyattempts have been made to surpass these dif ficulties.
29–31Sulfonated
PANis are the alternative way used to solve the problems of polymer
solubility and processability, bec ause the presence of these groups in
PANi structure affects the physicochemical properties of parent-polymer and is of great interest in crystallographic, optical, steric,
and electronic properties.32–36Sulfonated PANis are obtained by
several routes such as copolymerization of aniline with aniline como-
nomers containing sulfonic groups,37–39the direct ring-sulfonation of
emeraldine base form with fuming sulfuric acid, when –SO3Hg r o u p s
a r ei n t r o d u c e da tt h ea r o m a t i cr i n g ,40,41the treatment of emeraldine
base of PANi with 1,3-propanesul fone or 1,4-butanesulfone in the
presence of sodium hydride,42,43and chemical and electrochemical
polymerization of sulfonated monomers.44–47In a prior research, we
obtained by chemical homopolymerization of aniline- N-propan sul-
fonic acid, using ammonium persulfate (APS) as oxidant, both inacidic (1 M HCl solution) or aqueous solution polyaniline- N-propan
sulfonic acid (poly[AnPS]), and polymer used in this paper as gassensor.
47
An important trend is the development of devices and sensors based
onflexible substrates. The most used substrate to detect the sensors
properties is ITO, but as it is brittle, it can be easily degraded and losethe conductivity and the sensing character.
4,48Other substrates used
for depositing the polymer for applications of gas detection and
humidity sensors are thermal plastics materials, ceramics, or sili-
con.49The combination of PANi and various inorganic metals or
© 2019 Wiley Periodicals, Inc.
47743 (1 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743

metal oxides has resulted in materials with synergistic properties that
make use of the catalytic effect of the metal or metal oxide and has
developed new gas and humidity sensors.21,50,51In our previous
work, by in situ polymerization of aniline in the presence of iron-
oxide particles, we synthesized PANi-Fe 2O3nanoparticles and have
investigated structures, morphologies, and sensing properties.19,52
Poly (ethylene terephthalate) (PET) is one of the flexible substrates used
to deposit polymers to fabricate se nsor devices and for the improve-
ment the mechanical, electrical, di electric, and other properties,53,54
and for this reason, we used PET film in this article.
The aim of present study is to examine the morphology and sens-
ing properties of humidity or gases, like acetone, carbon monox-ide, carbon dioxide, ethylene, propane, and lique fied petroleum
gas (LPG), of conductive poly(AnPS) powder, or the aqueous
solution of polymer deposited on the PET film. Humidity flexible
sensor was fabricated by dipping the polymer solution obtainedbyin situ polymerization, on PET substrate, and it was character-
ized using different techniques.
EXPERIMENTAL
Materials
Aniline N-propanesulfonic acid (AnPS) and the homopolymer,
poly(AnPS), were synthesized as reported in other paper.47Ammo-
nium persulfate (APS), hydrochloric acid and acetonitrile (all fromAldrich) were used as received. Freshly bidistilled water was used toprepare all aqueous solutions. Poly (ethylene terephthalate) (PET)film roll was used as a flexible substrate for the construction of sensor
device and was cleaned with acetone and finally dried at 70
/C14Cb e f o r e
use. The synthesis of aniline-N-propanesulfonic acid (AnPS) and of
homopolymer poly(AnPS) was reported in other paper.47
CharacterizationFTIR spectra were recorded on KBr pellets and by ATR using aDIGILAB-FTS 2000 spectrometer. The UV –vis spectra of the com-
posites were measured using an UV –Vis SPECORD 200 Analytik
Jena spectrometer (Analytik Jena AG, Jena, Germany). XRD mea-
surements were performed with a Bruker AD8 Advance (USA) dif-
fractometer. The X-ray beam was CuK α1 (1.5406 A) radiation
operating from a sealed tube operated at 40.0 kV and 30 mA. Datafrom 3
/C14to 60/C14(2θ) were obtained using the Bragg –Brentano geome-
try at a scan rate 1.0/C14/min. The morphology of polymer was studied
by scanning electron microscopy (SEM) using a Scanning ElectronMicroscopy Quanta 200 apparatus and optical images were investi-
gated using the optical microscope Leica DM 2500M. Thermal gravi-
metric analysis (TGA) was performed by means of Netzsch STA449F1 Jupiter, in nitrogen stream with a heating speed of 10
/C14C/min
(30–900/C14C) and the sample weight of 8 –9m g .
In order to perform humidity sensitivity studies, the poly(AnPS)/
PETfilm was inserted between two gold electrodes on an LCR meter.
The electrical resistivity and electrical permittivity investigations of
the sensor sample, in the frequency range of 20 Hz –20 MHz, were
performed at the known levels of humidities.
For electrical properties versus temperature and sensibility studies of
the various gases, the poly(AnPS) powder was pressed using ahydraulic press into the disk-shaped sample with thickness about1 mm and diameter 6 mm. For the gas-sensing investigation, silvercontact electrodes were deposited on both the surfaces of the pellets.
The sensitivity of the sample “S”represented in Figure 10 was calcu-
lated according to the relation:
S=
ΔR
Rair=Rair−Rgas
Rairð1Ț
where Rairis the electrical resistance of sample in air and Rgasis
the electrical resistance in the presence of the gas.
The electrical measurements were performed using a high-
frequency LCR Meter Wayne Kerr 6500P.
RESULTS AND DISCUSSIONS
The sensor device was prepared by dipping the polymer solution on
the PET film. First, the polymer was synthesized by chemical oxida-
tive polymerization of AnPS. A solution of AnPS monomer dissolvedin 1 M HCl was introduced into an Erlenmeyer flask and was kept at
0–5
/C14C. The solution was continuously stirred using a magnetic stir-
rer. After about 30 min, APS was added in drops, with a droppingfunnel, to the reaction mixture and the stirring was continued. The
color of solution becomes green after few minutes. Then, after 24 h
of stirring, the poly(AnPS) was separated by precipitation in acetone,filtration, and drying. Finally, the powder of polymer was dissolved
in water and deposited with a syringe onto the PET film in multiple
layers by dripping, as illustrated in Figure 1.
FTIR and UV –Vis Spectroscopy
For obtaining the detailed structural information about poly(AnPS)
and PET films, FTIR spectra were recorded. Figure 2 shows the IR
spectra of poly(AnPS) powder, PET film, and polymer deposited on
PET film. For poly(AnPS), characteristic bands are observed at
1570 cm
−1(CC stretch of quinoid ring), 1505 cm−1(benzenoid
ring), 1329 cm−1(CN stretching in the benzenoid and quinoid
imine), 1040 cm−1, and 1176 cm−1(asymmetric and symmetric sul-
fonic groups 0 = S = 0 stretching vibrations). The most importantabsorption bands in the PET film spectrum can be identi fied at
1712 cm
−1attributed to carbonyl stretching vibration, 1408 cm−1
resulting from phenyl ring vibration, 1338 cm−1(~CH 2-wagging)
originate from trans glycol segment, 1242 cm−1, band characteristic
of ester group, 1016 cm−1assigned to ring C-C-C, 871 cm−1and
721 cm−1belong to C-H and C-O out of plane bending.50The IR
spectrum of poly(AnPS) deposited on the PET film presents bands ’
characteristic of both partners, the absorption band at 1709 cm−1
due to carbonyl stretching vibration of PET film, bands at 1578 and
1490 cm−1attributed to quinoid and benzenoid ring stretching
vibration of poly(AnPS), peak at 1307 cm−1corresponding to C N
stretching of a secondary amine and peaks at 1116 cm−1,a n d
1022 cm−1assigned to the symmetric and asymmetric sulfonic
group stretching vibration. In the FTIR spectrum of materialobtained by us, it can be seen that the bands ’characteristics to the
symmetric and asymmetric sulfonic groups to poly(AnPS) areshifted to lower wavenumbers in comparison with those reported for
poly(AnPS) powder and this can be explained by apparition of some
interactions between poly(AnPS) and PET, but we did not study thenature of these interactions.
The UV –vis spectra of poly(AnPS) were measured in aqueous
solution and are shown in Figure 3. The spectrum of self-dopedpoly(AnPS) exhibited the typical bands of other N-substitutedARTICLE WILEYONLINELIBRARY.COM/APP
47743 (2 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743

PANis.55–57The band at 320 nm corresponding to π-π*transi-
tion in benzene ring and the bands that appear at 430 nm andabove 1000 nm are due to optical absorptions of the localizedand delocalized polarons, respectively.
47The UV –Vis spectrum
of poly(AnPS)&PET film contains two shoulders at 330 nm and,
respectively, at 430 nm. The first shoulder corresponding to π-π*
transition of aromatic ring of benzene, respectively the second topolaron absorption in the doped poly(AnPS).
X-Ray Diffraction and SEM
The structure of the poly(AnPS) was investigated by XRD measure-ment The undoped PANi in the emeraldine base state correspondsto highly amorphous polymer. In Figure 4 is illustrated the XRD pat-tern of poly(AnPS), which shows crystalline peaks, indicating a high
degree of crystallinity, and this can be explaining the periodicity par-
allel to the polymer chain. The highly ordered structures of self-doped PANi-N alkane sulfonates have been evidenced by Kim et al.
,
which have clari fied the ionic interactions between propane sulfonateanions and the imine nitrogens from the main chain resulting in the
layering of the PANi chains.58The aqueous solution of polymer
developed also highly liquid crystalline phases with high orienta-tional and positional order associated with ionic interactions
between alkyl sulfonates groups and PANi main chain.
The SEM images of poly(AnPS), PET, and poly(AnPS) deposited on
PETfilm are shown in Figure 5. The morphology of the poly(AnPS)
film prepared by drop-casting over glass substrate shows a plate like
feature with 100 –200μm sizes resulted from aggregation of small
and irregular particles of different shapes and dimensions. In themicrographs of PET substrate, it can be clearly seen a nano fibrous
morphology. Morphological analysis of poly(AnPS) deposited by
drop on PET not presents major changes on the surface of PET film
in comparison with the SEM image of the poly(AnPS). It can be eas-ily seen in the SEM image that after deposition of the polymer, anirregular morphology formed by many nanoplates and nanoparticlesof poly(AnPS) aggregates into nano fibers of the PET film.
These statements are also supported by the microscopic images
of PET and poly (AnPS) deposited on the PET film as observed
in Figure 6.
Figure 1. Polymerization of AnPS and deposition on PET film. [Color figure can be viewed at wileyonlinelibrary.com]
Figure 2. FT-IR spectra (KBr pellet) of poly(AnPS), respectively, ATR of
PET film and poly(AnPS)&PET.
Figure 3. Absorption spectra (H 2O) of poly(AnPS) and poly (AnPS)
&PET film. [Color figure can be viewed at wileyonlinelibrary.com]ARTICLE WILEYONLINELIBRARY.COM/APP
47743 (3 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743

Thermogravimetric Analysis
The thermal stability of the poly(AnPS) was evaluated by TG analysisin nitrogen atmosphere and is presented in Figure 7. The initial massloss was observed between 50 and 120
/C14C and is assigned to the
residual water and solvent. The next weight loss process, with maxi-mum at 240
/C14C, is due to the scission and exclusion of alkyl sulfonate
group. The last weight loss observed after the removal of alkylsulfonate group occurred due to the complete degradation and
decomposition of the polymer main chain.59
Humidity and Gas Sensing Characteristics
Investigation of electrical properties of poly(AnPS)&PET film provides
important information about the behavior of this material as humiditysensors. The electrical measurements under humidity vapors ’influence
were performed in a closed enclosure at room temperature with knownvalues of humidity. The electrical chara cteristics of electr ical resistivity
and permittivity of as-obtained poly(AnPS)&PET film depending on
frequency and humidity are represented in Figure 8.
In Figure 8(a), it can be observed that the relative permittivity of
poly(AnPS)&PET film decreases with the frequency and increases
with the increase in humidity.
60,61From Figure 8(b), it can be
observed that the electrical resistivity decreases with humidityand frequency.
62
As expected, due to a smaller surface area, the electrical responseof massive material under the action of humidity is much lowerthan the film material, this being re flected in a lower humidity
sensitivity of a bulk material (see Figure 8).
Investigation of electrical properties of pellets sample provides
important information about the behavior of this material as gas sen-
sors. The electrical measurements under gas vapors in fluence were
performed in a closed enclosure with known gas concentration
Figure 4. XRD pattern of poly(AnPS).
Figure 5. SEM images of (a) poly(AnPS), (b) PET film, and (c) poly(AnPS)&PET film.
Figure 6. Microscopic images of (a) PET film and (b) poly(AnPS)&PET film. [Color figure can be viewed at wileyonlinelibrary.com]ARTICLE WILEYONLINELIBRARY.COM/APP
47743 (4 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743

(200 ppm) and controlling temperature using a Cromel –Alumel
thermocouple located in the close proximity of the sample.63,64The
electric capacitance and electric resistance of the sample were
recorded at fixed temperatures, both in air and in the presence of the
test gas using a digital LCR meter (Wayne Kerr 6500P) at 20 Hz. Theelectrical characteristics of electrical permittivity and resistivity of
pellet sample depending on temperature are represented in Figure 9.
As can be seen in Figure 9(a), there is a slight increase in electri-
cal permittivity up to 170/C14C, after which an important increase
is observed. The variation in the electrical resistivity as can beseen in Figure 9(b) shows two distinct regions: the first region
with the temperature range 22 –115
/C14C in which the electrical
resistivity increases with the increasing temperature and the sec-ond region with the temperature range 115 –225
/C14C where the
electrical resistivity shows a downward trend.
Figure 10 shows the sensitivity to tested gases recorded for sam-
ple as a dependence of temperature toward a constant 200-ppm
gas concentration. An optimal operating temperature around130
/C14C is observed, for both organic and inorganic gases. With
the exception of ethane, it is found that the sensitivity to organicgases is lower than the tested inorganic gases.
According to the experimental results disused by us, it can be
seen that the sensor based on poly(AnPS) obtained by simple
and low-cost techniques has good performances. It emerges thathumidity and low operating temperature observed for different
organic and inorganic gases are factors that affect the sensor
response for this material.
Figure 7. TG, DTG, and DTA curves of poly(AnPS). [Color figure can be
viewed at wileyonlinelibrary.com]
Figure 8. (a) Electrical permittivity and (b) electrical resistivity for obtained PET film; (c) electrical permittivity and (d) electrical resistivity for poly(AnPS)
compacted powder depending on frequency and humidity. [Color figure can be viewed at wileyonlinelibrary.com]ARTICLE WILEYONLINELIBRARY.COM/APP
47743 (5 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743

CONCLUSIONS
Self-doped N-propansulfonic acid PANi was prepared by in situ
polymerization technique. Aqueous solution of polymer wasdeposited by dipping onto the PET substrate. The structure andmorphology of polymer being used in the form of powder ordeposited in multiple layers onto the PET film were proved using
FTIR, SEM, XRD, and UV spectroscopies.
Large-variation spectrum of electrical permittivity and resistivity for
poly(AnPS)&PET film under humidity in fluence suggests its appli-
cations as humidity sensors. The relatively low operating tempera-
ture observed for different organic and inorganic gases indicates theuse of the material as an active element for general gas sensors.
REFERENCES
1. Mir, M. A.; Bhat, M. A.; Majid, S. A.; Lone, S. H.; Malla, M. A.;
Tiwari, K. R.; Pandit, A. H.; Tomar, R.; Bhat, R. A. J. Environ.
Chem. Eng. 2018 ,6,1 1 3 7 .
2. Chen, X.; Wong, C. K. Y.; Yuan, C. A.; Zhang, G. Sens.
Actuators B Chem. 2012 ,175, 15.
3. Doan, T. C. D.; Ramaneti, R.; Baggerman, J.; van der Bent, J. F.;
Marcelis, A. T. M.; Tong, H. D.; van Rijn, C. J. M. Sens. Actua-
tors B Chem. 2012 ,168, 123.4. Kumar, L.; Rawal, I.; Kaur, A.; Annapoorni, S. Sens. Actua-
tors B Chem. 2017 ,240, 408.
5. Ariyageadsakul, P.; Vchirawong kwin, V.; Kritayakornupong, C.
Sens. Actuators B Chem. 2016 ,232, 165.
6. Tudorache, F.; Popa, P. D.; Dobromir, M.; Iacomi, F.
Mater. Sci. Eng. B .2013 ,178, 1334.
7. Dhawale, D. S.; Salunkhe, R. R.; Patil, U. M.; Gurav, K. V.;
More, A. M.; Lokhande, C. D. Sens. Actuators B Chem.
2008 ,134, 988.
8. Joshi, S. S.; Lokhande, C. D.; Han, S. H. Sens. Actuators B
Chem. 2007 ,123, 240.
9. Basaka, S. P.; Kanjilal, B.; Sarkara, P.; Turnerb, A. P. F.
Synth. Met. 2013 ,175, 127.
10. Tudorache, F.; Rezlescu, N.; Tudorache, N.; Catargiu, A. M.;
Grigoras, M. Adv. Mat. 2009 ,3, 379.
11. Xie, L.-H.; Liu, X.-M.; He, T.; Li, J.-R. Chem. 2018 ,4,1 .
12. Kumar, R.; Yadav, B. C. Mater. Lett. 2016 ,167, 300.
13. Fratoddi, I.; Venditti, I.; Cametti, C.; Russo, M. V. Sens.
Actuators B Chem. 2015 ,220, 534.
14. Bai, H.; Shi, G. Sensors .2007 ,7, 267.
1 5 . R o z n y a t o v s k a y a ,N .V . ;M i r s k ,V .M . ;L a n g e ,U . Anal. Chim. Acta .
2008,614,1 .
16. Nohria, R.; Khillan, R. K.; Su, Y.; Dikshit, R.; Lvov, Y.;
Varahramyan, K. Sens. Actuators B Chem. 2006 ,114, 218.
17. Chen, X.; Zhou, G.; Mao, S.; Chen, J. Environ. Sci. Nano .
2018 ,1-3,1 .
18. Prathap, M. U. A.; Rodriguez, C. I.; Sadak, O.; Guan, V.;
Gunasekaran, S. Chem. Commun. 2018 ,54, 710.
19. Yoon, H.; Jang, J. Adv. Funct. Mater. 2009 ,19, 1567.
20. Tudorache, F.; Grigoras, M. Optoelectron. Adv. Mat. 2010 ,
4, 43.
21. Syrovy, T.; Kubersky, P.; Sapurina, I.; Pretl, S.; Bober, P.;
Syrova, L.; Hamacek, A.; Stejskal, J. Sens. Actuators B
Chem. 2016 ,225, 510.
22. Zhu, G.; Zhang, Q.; Xie, G.; Su, Y.; Zhao, K.; Du, H.;
Jiang, Y. Chem. Phys. Lett. 2016 ,665, 147.
23. Jang, J.; Ha, J.; Cho, J. Adv. Mater. 2007 ,19, 1772.
Figure 9. (a) Electrical permittivity and (b) electrical resistivity depending on temperature. [Color figure can be viewed at wileyonlinelibrary.com]
Figure 10. The dependence of the gas sensitivity versus operating tempera-
ture. [Color figure can be viewed at wileyonlinelibrary.com]ARTICLE WILEYONLINELIBRARY.COM/APP
47743 (6 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743

24. Virji, S.; Huang, J.; Kaner, R. B.; Weiller, B. H. Nano Lett.
2004 ,4, 491.
25. Mak, C. A.; Pericas, M. A.; Fagadar-Cosma, E. Catal.
Today .2018 ,306, 268.
2 6 . C h e n ,Q . ;P e i ,Z . ;X u ,Y . ;L i ,Z . ;Y a n g ,Y . Chem. Sci. 2018 ,9, 623.
27. Huang, J.; Virji, S.; Weiller, B. H.; Kaner, R. B. Chem.
Eur. J. 2004 ,10, 1314.
28./C19Ciri/C19c-Marjanovi /C19c, G. Synth. Met. 2013 ,177,1 .
29. Rizzo, G.; Arena, A.; Donato, N.; Latino, M.; Saitta, G.;
Bonanita, A.; Neri, G. Thin Solid Films .2010 ,518, 7133.
30. Pud, A.; Ogurtsov, N.; Korzhenko, A.; Shapoval, G. Prog.
Polym. Sci. 2003 ,28, 1701.
31. Solonaru, A. M.; Grigoras, M. EXPRESS Polym. Lett. 2017 ,
11, 127.
32. Grigoras, M.; Catargiu, A. M.; Tudorache, F. J. Appl. Polym.
Sci.2013 ,127, 2796.
33. Wei, X. L.; Wang, Y. Z.; Long, S. M.; Bobeczko, C.;
Epstein, A. J. J. Am. Chem. Soc. 1996 ,118, 2545.
34. Yue, J.; Epstein, A. J. J. Am. Chem. Soc. Chem.Commun.
1992 ,21, 1540.
35. Lu, Y.; Li, W.; Zhang, J.; Liu, Y.; Casey, P.; Bateman, S.;
Shen, S. Z.; Zhou, J.; Zakharova, G. S.; Chen, W. Ferroelec-
trics.2015 ,477(1), 93.
36. Gao, X.; Xu, L.-P.; Zhou, S.-F.; Liu, G.; Zhang, X. Am.
J. Biomed. Sci. 2014 ,6(1), 41.
37. Gopalan, S. A.; Gopalan, A. I.; Lee, K. P.; Venkatesan, S.;
Kang, B. H.; Lee, S. W.; Lee, J. S.; Qiao, Q.; Kwon, D. H.;Kang, S. W. Sol. Energy Mater. Sol. Cell .2015
,141, 275.
38. Xu, Y.; Dai, L.; Chen, J.; Gal, J. Y.; Wu, H. Eur. Polym. J.
2007 ,43, 2072.
39. Shimizu, S.; Saitoh, T.; Uzawa, M.; Yuasa, M.; Yano, K.;
Maruyama, T.; Watanabe, K. Synth. Met. 1997 ,85, 1337.
40. Mav, I.; Zigon, M.; Sebenik, A.; Vohlidal, J. J. Polym. Sci.
Polym. Chem. 2000 ,38, 3390.
41. Yue, J.; Epstein, A. J. J. Am. Chem. Soc. 1990 ,112, 2800.
42. Yue, J.; Zhao, H.; Wang, Z. H.; Keith, R.; Cromack, K. R.;
Epstein, A. J.; MacDiarmid, A. G. J. Am. Chem. Soc. 1991 ,113,
2665.
43. Chen, S. A.; Hwang, G. W. J. Am. Chem. Soc. 1994 ,116,7 9 3 9 .44. Chen, S. A.; Hwang, G. W. J. Am. Chem. Soc. 1995 ,117,
10055.
45. Royappa, A. T.; Steadman, D. D.; Tran, T. L.; Nguyen, P. T.;
Prayaga, C. S.; Cage, B.; Dalal, N. Synth. Met. 2001 ,123,2 7 3 .
46. Atkinson, S.; Chan, H. S. O.; Neuendorf, A. J.; Ng, S. C.;
Ong, T. T.; Young, D. J. Chem. Lett. 2000 ,29, 276.
47. Vacareanu, L.; Catargiu, A. M.; Grigoras, M. J. Anal. Methods.
Chem. 2012 ,2012, 11. https://doi.org/10.1155/2012/737013.
48. Grigoras, M.; Catargiu, A. M.; Tudorache, F.; Dobromir, M.
Iran. Polym. J. 2012 ,21, 131.
49. Qi, J.; Xinxin, X.; Liu, X.; Lau, K. T. Sens. Actuators B
Chem. 2014 ,202, 732.
50. Harsányi, G. Sens. Rev. 2000 ,20, 98.
51. Bairi, V. G.; Bourdo, S. E.; Sacre, N.; Nair, D.; Berry, B. C.;
Biris, A. S.; Viswanathan, T. Sensors .2015 ,15, 26415.
52. Li, Y.; Zhao, H.; Ban, H.; Yang, M. Sens. Actuators B Chem.
2017 ,245, 34.
53. Bendrea, A. D.; Grigoras, M.; Catargiu, A. M.; Tudorache, F.
J. Optoelectron. Adv. M. 2009 ,1,1 1 2 4 .
54. Kutanis, S.; Karakisla, M.; Akbulut, U.; Sacak, M. Compos.
Part A .2007 ,38, 609.
55. Duboritz, I.; Pud, A. Sens. Actuators B Chem. 2014 ,190,3 9 8 .
56. Nabid, M. R.; Entezami, A. A. Polym. Adv. Technol. 2005 ,
16,3 0 5 .
57. Bergeron, J. Y.; Dao, L. H. Macromolecules .1992 ,25, 3332.
58. Kim, E. K.; Lee, M. S.; Lee, M. H.; Rhee, S. B. Synth. Met.
1995 ,69, 101.
59. Kanhegaokar, S. A.; Chunji, G.; Choi, E. Y.; Kwon, O. P.;
Lee, S. H. J. Appl. Polym. Sci. 2011 ,120, 1138.
60. Petrila, I.; Popa, K.; Tudorache, F. Sens. Actuators A Phys.
2016 ,247, 156.
61. Tudorache, F.; Petrila, I.; Popa, K.; Catargiu, A. M. Appl.
Surf. Sci. 2014 ,303, 175.
62. Petrila, I.; Tudorache, F. Superlattices Microstruct. 2014 ,70, 46.
63. Tudorache, F.; Brinza, F.; Popa, P. D.; Petrila, I.; Grigoras, M.;
Tascu, S. Acta Phys. Pol. A .2012 ,121,9 2 .
64. Rambu, A. P.; Tudorache, F.; Petrila, I.; Rusu, G. G.;
Nica, V.; Dobromir, M.; Tascu, S. J. Mater. Sci. Mater. El.
2015 ,26, 9837.ARTICLE WILEYONLINELIBRARY.COM/APP
47743 (7 of 7) J. APPL. POLYM. SCI. 2019 , DOI: 10.1002/APP.47743