Comparison of the thermally stable conducting polymers PEDOT, PANi, and PPy using sulfonated poly(imide) templates

Article abstract of DOI:10.1016/j.polymer.2010.08.008

We showed that it is possible to use sulfonated poly(amic acid)s (SPAA) to template polymerize 3,4-ethylenedioxythiophene (EDOT) to PEDOT, resulting in an aqueous dispersion of conducting polymer. This study compares PEDOT with poly(aniline) (PANi) and poly(pyrrole) PPy using the same and another, more rigid, poly(amic acid) template. A variety of system parameters, including reaction time, conductivity, and overall thermal stability, were noted to change systematically depending on the systems chosen. PANi-SPAA takes less than one tenth of the reaction time of PEDOT-SPAA (12 h versus 7 days), and results in higher conductivities at room temperature (ca. 10 S/cm). However, it is not as thermally stable as the PEDOT-SPAA system; conductivity is not measureable after annealing at 300 °C. PPy-SPAA was found to be more thermally stable than PANi-SPAA (less mass lost at 300 °C), but it was still more conductive than un-doped PEDOT-SPAA by a factor of 1000 (ca. 1.0 S/cm).

Full text of DOI:10.1016/j.polymer.2010.08.008

Polymer 51 (2010) 4472e4476
Contents lists available at ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Comparison of the thermally stable conducting polymers PEDOT, PANi,
and PPy using sulfonated poly(imide) templates
a
a
b
a
Bongkoch Somboonsub , Suttisak Srisuwan , Michael A. Invernale , Supakanok Thongyai ,
a
b
b,
*
Piyasan Praserthdam , Daniel A. Scola , Gregory A. Sotzing
Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University,
Bangkok 10330 Thailand
a
b
University of Connecticut, Department of Chemistry and the Polymer Program, 97 North Eagleville Road U-3136, Storrs, CT 06269-3136, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 April 2010
Received in revised form
We showed that it is possible to use sulfonated poly(amic acid)s (SPAA) to template polymerize 3,4-
ethylenedioxythiophene (EDOT) to PEDOT, resulting in an aqueous dispersion of conducting polymer.
This study compares PEDOT with poly(aniline) (PANi) and poly(pyrrole) PPy using the same and another,
more rigid, poly(amic acid) template. A variety of system parameters, including reaction time, conduc-
tivity, and overall thermal stability, were noted to change systematically depending on the systems
chosen. PANi-SPAA takes less than one tenth of the reaction time of PEDOT-SPAA (12 h versus 7 days),
and results in higher conductivities at room temperature (ca. 10 S/cm). However, it is not as thermally
3
August 2010
Accepted 6 August 2010
Available online 13 August 2010
Keywords:
ꢀ
stable as the PEDOT-SPAA system; conductivity is not measureable after annealing at 300 C. PPy-SPAA
Conducting polymers
Template polymerization
Thermal stability
ꢀ
was found to be more thermally stable than PANi-SPAA (less mass lost at 300 C), but it was still more
conductive than un-doped PEDOT-SPAA by a factor of 1000 (ca. 1.0 S/cm).
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
film. However, conducting polymer polymerizations with this
traditional template show degradation after annealing above
ꢀ
Conducting polymers (CPs) are of increasing interest, especially
in areas such as electronic devices. They are used as a transparent
anode in the field of optical electronics, demonstrating applications
such as light detection [1], electrochromic displays [2], organic light
emitting diodes (OLEDs) [3], and optical displays [4]. Of the many
interesting conducting polymers that have been developed over the
past decade, those based on poly(aniline) or PANi [5], poly(3,4-
ethylenedioxythiophene) or PEDOT [6,7], and poly(pyrrole) or PPy
200 C, particularly resulting in a decrease or total loss of con-
ductivity. This is a problem for high-temperature processing
conditions, such as melt-coating with polycarbonate. Applications
where devices use layers of PEDOT-PSS, such as photovoltaic cells
or skyscraper windows, will experience losses of function over time
or complete device failure if subjected to high temperatures over
long periods of time, as well. To address these obstacles, new
templates which can resist higher temperatures for annealing and
that can also anneal for longer times than traditional templates
were studied in this work. Sulfonated poly(amic acid) templates
were used, which were subsequently converted to the polyimide
upon annealing. The systems studied within use two different
chemical structures for the poly(amic acid), as well as three
different conducting polymers, to assess the function and benefits
of one system over another.
[
8] are of significant importance due to their low costs [9], low
densities [10], and their light weights [10] (in comparison to metals
or other inorganic materials). As a result, these conducting poly-
mers have attracted much attention in organic electronics. PEDOT
is among the most popular conducting polymers. It has shown high
conductivity, ranging from 10 to 10 S/cm [11]. The issue with
PEDOT alone is that it is an insoluble polymer, like many CPs. The
use of template polymerization in the presence of a polyanion
template, such as poly(styrene sulfonic acid) (PSSA), is one solution
for this issue. It results in the formation of a colloidal dispersion of
PEDOT-PSS nanoparticles that can then be cast as a thin, conductive
ꢁ
2
5
Poly(imide)s are well-known high-temperature polymers
because they have several advantages, including thermal stability
[12], mechanical properties [13] thermoxidative stability [14], and
superior chemical resistance [15]. The success of Kapton by DuPont
was the first well-known commercial poly(imide) film which can
ꢀ
remain stable over a wide range of temperatures, from 273 C to
ꢀ
4
00 C. It has been used in the manufacture of integrated circuits
*
Corresponding author. Tel.: þ1 860 486 4619; fax: þ1 860 486 4745.
E-mail address: sotzing@mail.ims.uconn.edu (G.A. Sotzing).
[16] and also in gas membrane separators [16]. Kapton is produced
0
032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2010.08.008

B. Somboonsub et al. / Polymer 51 (2010) 4472e4476
4473
from the condensation of pyromellitic dianhydride (PMDA) and
3
(SO , 20%), poly(styrene sulfonic acid) (18 wt.% in water), iron (III) p-
0
0
4
,4 -diaminodiphenyl ether (4,4 -ODA), which is a rigid structure
toluene sulfonate hexahydrate, 3,4-ethylenedioxythiophene (EDOT),
lithium trifluoromethanesulfonate, N,N-dimethylformamide (DMF),
and aniline were purchased from SigmaeAldrich. EDOT was distilled
for a polyimide. Pineri and co-workers [17] first synthesized
sequenced five-membered and six-membered ring sulfonated
0
0
0
polyimides from 4,4 -diaminobiphenyl-2,2 -disulfonic acid (BDSA),
4
before use. 4,4 -Hexafluoroisopropylideneoxydiphthalic anhydride
0
,4 -oxydianiline (ODA), and two types of dianhydrides, oxy-
(6FDA) was purchased from TCI America. Pyrrole, ammonium
persulfate, concentrated sulfuric acid (95%), sodium hydroxide
(NaOH), hydrochloric acid (HCl), and acetone were purchased from
diphthalic dianhydride (O-DDPA) and 1,4,5,8-naphthalenete-
tracarboxylic dianhydride (NTDA), respectively. Okamoto et al. have
0
Ò
studied sulfonated poly(imide)s which use 4,4 -ODADS as
Fisher Scientific and were used as received. Surfynol 2502surfactant
a diamine for proton exchange membrane (PEM) fuel cell systems
was purchased from Air Products, Inc. d-Sorbitol 97%, ion-exchange
þ
[18]. We used this diamine, along with a more flexible dianhydride,
resin DOWEX 50W ꢂ 8 50e100 mesh, and Amberlite* IR-120 (Na
to synthesize a new sulfonated poly(amic acid) that can be used as
a template to form PEDOT. This template can then undergo
a conversion to the thermally stable sulfonated poly(imide) form by
form) were purchased from Acros Organics. Sodium poly(styr-
enesulfonate) was purchased from Polysciences, Inc. Dialysis tubes
(Molecular weight cut off [MWCO] ¼ 3.5e5 kDa) were purchased
from Spectrum Laboratories Inc.
ꢀ
annealing at greater than 150 C for a short time. This form of the
conductive composite resisted higher temperatures than tradi-
tional PEDOT-PSS [19]. This work is an expansion of this principle
and has studied two different templates to investigate the effect of
the structure of poly(imide) on the properties of a variety of
popular conducting polymers.
2
2
.2. Preparation of monomers and sulfonated poly(amic acid)s
0
0
.2.1. Synthesis of 4,4 -diaminodiphenyl ether-2,2 -disulfonic acid
0
(4,4 -ODADS)
Herein, the template polymerization of conducting polymers
has been accomplished using three different conducting polymers
To a 100 mL three-neck flask with a stirring device was added
0 0
.00 g (10.0 mmol) of 4,4 -diaminodiphenyl ether (4,4 -ODA). The
2
(
(
PEDOT, PANi, and PPy) as well as two sulfonated poly(amic acid)s
SPAA1 and SPAA2). The chemical structures of each system are
flask was cooled in an ice bath, and then 1.7 mL of concentrated
0
(95%) sulfuric acid was slowly added with stirring. After 4,4 -ODA
shown in Fig. 1. These CPs represent three of the broadest and most
popular classes of materials. Polymers based on anilines, pyrroles,
and thiophenes have all seen commercialized success in some form.
The templates were chosen because of their differences in rigidity.
The result of each template polymerization was a colloidal disper-
sion in water. These systems were explored in terms of reaction
time, thermal stability, mass loss with time, and conductivity
response to common dopants and annealing temperatures. Con-
trols for all systems were prepared in the form of in-house poly-
merizations using the PSSA template for each CP that was used.
was completely dissolved, 10.5 mL of fuming (SO
3
20%) sulfuric acid
was slowly added to the flask. The reaction mixture was stirred at
ꢀ
ꢀ
C for 2 h and then slowly heated to 80 C and kept at this
0
temperature for an additional 3 h. After cooling to room tempera-
ture, the slurry solution mixture was carefully poured onto 20 g of
crushed ice. The resulting white precipitate was filtered off and
then re-dissolved in a sodium hydroxide solution. The basic solu-
tion was filtered, and the filtrate was acidified with concentrated
hydrochloric acid. The solid was filtered off, washed with water and
ꢀ
methanol successively, and dried at 80 C in vacuum oven over-
night [18]. (87.17% yield).
2
. Experimental
2.2.2. Synthesis of sulfonated poly(amic acid)s (SPAA1, SPAA2)
2
.1. Materials
To a 100 mL three-neck flask with N2 inlet and outlet was added
0
0
.5405 g (1.5 mmol) of 4,4 -ODADS, 6 mL of m-cresol, and 0.3643 g
0
0
0
0
4
,4 -Diaminodiphenyl ether (4,4 -ODA), 4,4 -oxydiphthalic anhy-
(3.6 mmol) of triethylamine. After 4,4 -ODADS was completely
dissolved, 0.4653 g (1.5 mmol) of O-DPDA for SPAA1 or 0.6664 g
3
dride (O-DPDA), triethylamine (Et N), m-cresol, fuming sulfuric acid
þ
þ
Fig. 1. Chemical structures of the various conducting polymers and the various templates used in this study, with their corresponding abbreviations (R ¼ H for PEDOT and PPy, Na
for PANi).

4
474
B. Somboonsub et al. / Polymer 51 (2010) 4472e4476
(
1.5 mmol) of 6FDA for SPAA2 were added and then stirred at room
2.6. Template polymerization of ANi and sulfonated poly(amic acid)
(PANi-SPAA1, PANi-SPAA2)
temperature for 24 h. When the reaction was complete, the reac-
tion mixture was decanted into acetone (75 mL), filtered, washed
ꢀ
with acetone (25 mL, 2 times), and dried at 50 C in a vacuum oven
To a 100 mL one neck flask, 49.36 mg (0.53 mmol) of ANi was
overnight [18]. (1.1463 g, 83.66% yield for SPAA1 and 1.3404 g,
introduced dropwise in 0.5 M aqueous HCl solution 40 mL and was
þ
8
5.31% yield for SPAA2).
stirred for 1 h. Then, 47.34 mg (0.07 mmol) of SPAA1 Na form or
þ
5
4.32 mg (0.07 mmol) of SPAA2 Na form were added to the mixed
2
.2.3. Purification
The sulfonated poly(amic acid)s were purified via dialysis tube.
solution and were stirred for 1 h. The both polymerizations of ANi
were conducted with 157.46 mg (0.69 mmol) of APS. The reaction
mixtures were stirred vigorously for 12 h at room temperature
leading to a dark green dispersion [21].
SPAAs dissolved in water were loaded inside the dialysis tube and
soaked in DI water for 24 h, changing the water twice (2 times at
12 h each).
2.7. Template polymerization of Py and poly(styrenesulfonic acid)
2.2.4. Ion exchange
(PPy-PSS)
The purified SPAAs salt form were changed to SPAAs acid form
with an ion exchange resin of strong acid type DOWEX 50W ꢂ 8
To a 25 mL one neck flask, 10.06 mg (0.15 mmol) of Py and
(
cation exchange) in case using for polymerization with EDOT
290.4 mg of 18 wt.% PSSA aqueous solution were added. To this
suspension 108.40 mg (0.16 mmol) of iron (III) p-toluene sulfonate
hexahydrate was added. The total mass of all the reactants was
adjusted to 10 g by adding an appropriate amount of de-ionized
water. The reaction mixture was stirred vigorously for 24 h at room
temperature leading to a black dispersion [22,23].
þ
and purified with Amberlite* IR-120 (Na form) ion exchange
resin in case using for polymerization with aniline. The SPAAs
salt form were stirred in DI water with the ion exchange resin for
1
h to convert them to the free acid form (SO
3
H) and sulfonated
þ
poly(amic acid) sodium form (Na ); they were centrifuged and
filtered in a crucible filter and then dried at 50 C in vacuum oven
ꢀ
overnight. Molecular weight and molecular weight distributions
2.8. Template polymerization of Py and sulfonated poly(amic acid)
(PPy-SPAA1, PPy-SPAA2)
of SPAA1 and SPAA2 were Mn1 ¼ 20,769, Mw1 ¼ 35,502,
PDI
1
¼ 1.71 and Mn2 ¼ 18,627, Mw2 ¼ 39,442, PDI ¼ 2.12.
2
To a 25 mL one neck flask, 10.06 mg (0.15 mmol) of Py and
200.0 mg (0.30 mmol) of SPAA1 or 230.6 mg (0.30 mmol) of SPAA2
2.3. Template polymerization of EDOT and poly(styrenesulfonic
were added. To this suspension 108.40 mg (0.16 mmol) of iron (III)
p-toluene sulfonate hexahydrate was added for both polymeriza-
tions. The total mass of all the reactants was adjusted to 10 g by
adding appropriate amount of de-ionized water. The reaction
mixtures were stirred vigorously for 5 days at room temperature
leading to a black dispersion [22,23].
acid) (PEDOT-PSS)
To a 25 mL one neck flask, 21.3 mg (0.15 mmol) of EDOT and
2
90.4 mg of 18 wt.% PSSA aqueous solution was added. To this
suspension 108.4 mg (0.16 mmol) of iron (III) p-toluene sulfonate
hexahydrate was added. The total mass of all the reactants was
adjusted to 10 g by adding an appropriate amount of de-ionized
water. The reaction mixture was stirred vigorously for 24 h at room
temperature leading to a dark blue dispersion, purified according to
literature procedure [20].
2.9. Preparation of PEDOT, PANi, PPy with SPAA1 and SPAA2 films
Films were prepared by drop casting pristine films and doped
films onto glass slides at room temperature. The films were
ꢀ
ꢀ
annealed at 180 C for 10 or 90 min, and 300 C for 10 min for
improving conductivities with thermal treatment. Separate films of
each material were evaluated for conductivity at room temperature
after annealing. All films were also prepared with 5 wt.% of
2.4. Template polymerization of EDOT and sulfonated poly(amic
acid) (PEDOT-SPAA1, PEDOT-SPAA2)
To a 25 mL one neck flask, 21.3 mg (0.15 mmol) of EDOT and
Ò
d-sorbitol, 0.1 wt.% DMF, 0.1 wt.% Surfynol 2502, and with all three
2
00.0 mg (0.30 mmol) of SPAA1 or 230.6 mg (0.30 mmol) of
components simultaneously.
SPAA2 were added. To this suspension 108.4 mg (0.16 mmol) of
iron (III) p-toluene sulfonate hexahydrate was added for both
polymerizations. The total mass of all the reactants was adjusted
to 10 g by adding appropriate amount of de-ionized water. The
reaction mixtures were stirred vigorously for 7 days, 5 days for
PEDOT-SPAA1 and PEDOT-SPAA2, respectively at room tempera-
ture leading to a dark blue dispersion, purified according to
literature procedure [19].
2
.10. Measurements
Fourier transform infrared spectroscopy (FTIR) was performed
using a MAGNA-IR560. Spectra was taken on ground powder in
a KBr matrix with a scanning range of 500e4000 cm , 64 scans at
a resolution of 4 cm . Thermogravimetric Analysis (TGA) was
performed by a PerkineElmer TGA 7 series analysis system at
ꢁ1
ꢁ1
ꢀ
a heating rate of 20 C/min under air at a flow rate of 60 mL/min.
2
.5. Template polymerization of ANi and poly(styrenesulfonic acid)
Gel Permeation Chromatography (GPC) was done using a millipore
model 150-C GPC system; DMAC was used as the mobile phase. The
results were calibrated by standards of poly(methyl methacrylate).
(
PANi-PSS)
1
To a 100 mL one neck flask, 49.36 mg (0.53 mmol) of ANi was
Nuclear Magnetic Resonance (NMR) H NMR spectra were recorded
introduced dropwise in 0.5 M aqueous HCl solution 40 mL and
on a Bruker DMX-500 NMR Spectrometer. Conductivities were
measured using a four-line collinear array utilizing a Keithley
Instruments 224 constant current source and a 2700 Multimeter.
The polymer was coated on the glass substrate having four gold
coated leads on the surface across the entire width of the polymer
and 0.25 cm apart from each other. The current was applied across
the outer leads and voltage was measured across the inner leads.
ꢁ
þ
was stirred for 1 h. Then, 600.0 mg (0.07 mmol) of PSS Na was
added to the mixed solution and was stirred for 1 h. The poly-
merization of ANi was conducted with 157.46 mg (0.69 mmol) of
APS as an oxidizing agent. The reaction mixtures were stirred
vigorously for 12 h at room temperature leading to a dark green
dispersion [21].

B. Somboonsub et al. / Polymer 51 (2010) 4472e4476
4475
3
. Results and discussion
that PANi systems have higher conductivities than PPy and PEDOT
systems, at room temperature.
3
.1. Diamine monomer and PEDOT, PANi, PPy with sulfonated poly
After heat treatment, the chain alignment in the films will
change due to the differences in rigidity of the poly(amic acid) and
the poly(imide), leading to modified morphologies, which causes
the observed conductivity enhancement. For example, after
(
amic acid) templates
0
Firstly, we have synthesized the diamine monomer, 4,4 -di-
0
0
ꢀ
aminodiphenyl ether-2,2 -disulfonic acid (4,4 -ODADS) for use as
a material used to make the sulfonated poly(amic acid). Fuming
sulfuric acid was used as a sulfonated agent. The monomer structure
was confirmed by 1H NMR and FTIR. The FTIR spectrum shows
absorptions at a) 1031.8 and b) 1088.3 cm for the sulfonic acid
2
group,andatc)3481.7cm assignedtoNH ofthediamime. The new
template, sulfonated poly(amic acid) was synthesized with two
different dianhydrides. The first template (SPAA1), 4,4 -oxydiphthalic
anhydride (O-DPDA) is a dianhydride which has an ether bond (R-O-
R) between two aromatic positions. It is a flexible system. The second
template (SPAA2), 4,4 -hexafluoroisopropylideneoxydiphthalic an-
hydride (6FDA) is more thermally stable than the first template. The
structure of poly(amic acid) was confirmed with FTIR. The broad
absorption band at 3476.9 cm is assigned to the absorbed water in
the sample (the sulfonic acid groups are highly hydrophilic). The peak
at 1663.3 cm indicates the absorption bands of carbonyl group
annealing at 180 C for 10 min, the conductivity of PEDOT-SPI1 was
ꢁ
4
ꢁ3
increased from 2.04 ꢂ 10 S/cm to 5.83 ꢂ 10 S/cm, a 10-fold
enhancement, but the conductivity of PANi-SPI1 decreased slightly
from 7.74 S/cm to 2.88 S/cm. PPy-SPI1 did not significantly change,
ꢁ1
ꢁ2
ꢁ2
however, (from 3.47 ꢂ 10 to 5.00 ꢂ 10 , which is within the
standard deviation for these measurements). The chain rear-
rangements that caused a more marked increase for the PEDOT
system appear to have less of an affect on PANi and PPy. The
exhaustive results of all conductivities measured are shown in the
Supporting Information, including all annealing and doping studies
using d-sorbitol and other common additives. For ease of compar-
ison, the highest achieved conductivity for each material synthe-
sized herein is shown in Fig. 2. We found that the PANi systems had
higher conductivities than PPy and PEDOT systems. The conduc-
ꢁ1
0
0
ꢁ
1
ꢁ
4
tivities of PEDOT systems were increased from 2.04 ꢂ 10
to
ꢁ
1
ꢁ3
ꢀ
5.83 ꢂ 10 S/cm, after annealing at 180 C for 10 min and increased
ꢁ1
ꢁ4
ꢁ4
ꢀ
(
CONH) and peak at ca. 2500e3500 cm indicate the absorption
from 2.04 ꢂ 10 to 6.47 ꢂ 10 S/cm, after annealing at 300 C for
bands of the carboxylic acid (COOH). The sulfonic acid groups (SO H)
appears at 1029.0 cm , which confirmed formation of the prepared
sulfonated poly(amic acid). After annealing at 180 C for short curing
time, the strong absorption band around 1719.7 cm is assigned to
3
10 min. In the PPy systems, conductivities were increased from
ꢁ
1
ꢁ2
ꢁ2
ꢀ
3.47 ꢂ 10 to 5.00 ꢂ 10 S/cm only annealing at 180 C for 10 min,
ꢀ
ꢀ
but at 300 C for 10 min the conductivities decreased from
ꢁ
1
ꢁ2
ꢁ3
3.47 ꢂ 10 to 8.33 ꢂ 10 S/cm. In the case of the PANi systems,
conductivities were decreased by increasing temperature, but
PEDOT-based films exhibited a 3-fold improvement after annealing
the symmetric imide C]O stretching, and also the peak at
ꢁ
1
1778.6 cm indicates the asymmetric imide C]O stretching, which
ꢀ
confirmed the complete imidization to sulfonated poly(imide)
at 180 C for 90 min and also a 3-fold improvement for the SPI1
ꢁ
4
ꢁ4
(
details in Supporting Information).
template (from 1.02 ꢂ 10 S/cm to 2.96 ꢂ 10 S/cm), and a 6-fold
ꢁ
4
ꢁ4
The conducting polymers were chosen due to their broad
increase from 1.02 ꢂ 10 S/cm to 6.06 ꢂ 10 S/cm after annealing
ꢀ
popularity in academia and industry. The templates were chosen on
the basis of differences in rigidity. If a too-rigid template is chosen,
either it will not be soluble in water when sulfonated or it will not
allow for the templating of a conducting polymer. We have
observed a failure to template polymerize when using sulfonated
Kapton, for example, which is more rigid than our SPAA1 or SPAA2
systems when converted to their imide forms. The system chosen
for SPAA2 was more rigid than SPAA1, but it was not so rigid as to
disallow formation of the templated CP in any case. Balancing this
issue is a key element to obtaining a usable template system.
Further, reaction times have varied with the different systems. The
control reaction for each CP takes 24 h (PSSA template). PEDOT-
SPAA1 takes 7 days, but using SPAA2 required 5 days. PANi was
much faster, overall, taking on the order of 12 h, regardless of the
template. PPy systems achieved templating in 5 days, as well.
at 300 C for 10 min (PEDOT-SPI1). PANi-SPI1 and PANi-SPI2 could
ꢀ
no longer be measured after annealing at 300 C, whereas PPy-SPI1
and PPy-SPI2 showed slightly lower conductivities. The conduc-
tivities of PPy-SPI1 and PPy-SPI2 at room temperature were
ꢁ
2
ꢁ3
3.47 ꢂ 10 S/cm and 3.63 ꢂ 10 S/cm, respectively, whereas PPy-
PSS was measured to be 2.47 S/cm. The highest value for PEDOT-
ꢁ2
SPAA1 was 8.99 ꢂ 10 S/cm, which was doped with DMF (0.1 wt.%)
ꢀ
and annealed at 180 C for 10 min (so, in reality, it was the PEDOT-
ꢁ
2
SPI1). The highest value for PEDOT-SPAA2 was 6.44 ꢂ 10 S/cm,
which was doped with d-sorbitol (5 wt.%). This means that the
PEDOT-SPAA systems had the highest increases in conductivity
ꢀ
(accomplished with 180 C annealed samples upon secondary
doping with common additives). For PANi systems, PANi-SPAA1
had the highest value, 7.74 S/cm, which was without heat treatment
3.2. Conductivity
The conductivity of PEDOT, PANi, and PPy each with SPAA1,
SPAA2, and PSS were all measured. In the cases where annealing
was performed, the form of the template is actually the imide, SPI1
and SPI2, because only 5e10 min is needed to convert these films
from the amic acid state. The second template (SPAA2) is less water
soluble than the first template (SPAA1), this was attributed as the
cause for a slight decrease in conductivity for systems using this
template. However, it became a dark blue dispersion faster than
PEDOT-SPAA1 (5 days as opposed to 7 days) indicating that the
reaction is still viable. Comparison of the same template (SPAA1) at
room temperature, the conductivities of PANi-SPAA1, PPy-SPAA1
ꢁ
2
and PEDOT-SPAA1 were 7.74 S/cm, 3.47 ꢂ 10
S/cm and
ꢁ
4
Fig. 2. Conductivities of each system. (P1 ¼ PEDOT-SPI1 doped with DMF 0.1 wt.% at
2
.04 ꢂ 10 S/cm, respectively. For SPAA2, the conductivities of
ꢀ
ꢀ
1
80 C, P2 ¼ PEDOT-SPAA2 doped with d-sorbitol 5 wt.% at 20 C, A1 ¼ PANi-SPAA1 at
ꢁ1
PANi-SPAA2, PPy-SPAA2 and PEDOT-SPAA2 were 7.34 ꢂ 10 S/cm,
ꢀ
ꢀ
20
C, A2 ¼ PANi-SPAA2 doped with DMF 0.1 wt.% at 20 C, Y1 ¼ PPy-SPAA1 doped
ꢁ3
ꢁ4
ꢀ
ꢀ
3
.63 ꢂ 10 S/cm and 1.96 ꢂ 10 S/cm, respectively. This shows
with DMF 0.1 wt.% at 20 C, Y2 ¼ PPy-SPI2 doped with DMF 0.1 wt.% at 180 C).

4
476
B. Somboonsub et al. / Polymer 51 (2010) 4472e4476
templating is possible for three classes of conducting polymers:
anilines, pyrroles, and thiophenes. Further, the resulting thermal
stabilities upon imidization of the template could lead to their use in
a variety of high-temperature applications or processing steps. The
rigidification of the template backbone causes a rearrangement of
the template conductor, resulting in a 10-fold increase in conduc-
tivity for PEDOT systems. As expected, certain systems possessed
advantages over others. PANi-SPAA took far less time to synthesize
and was more conductive overall, but did not survive higher
temperatures than its PSSA-based control. PEDOT-SPI exhibited the
highest thermal stability but had fairly low intrinsic conductivity.
Secondary doping was able to enhance it by two orders of magni-
tude, however. It also takes seven days to synthesize, which could be
a drawback for scalability. PPy systems seemed to balance these
advantages and constraints, allowing for better thermal stability
than PANi with slightly lower conductivities, yet higher conductivi-
ties than PEDOT-SPAA with lower thermal stability. It is clear that,
depending on the desired use of these organic conductors, one has
the ability to choose a class of materials that will suit their needs.
Finally, we have observed that the more rigid the initial template, the
lower the conductivity of the final sample. By choosing a more rigid
second template, SPAA2, we were able to achieve higher thermal
stability at a slight cost to the conductivity. The trends observed here
serve to display the obvious tunability of this approach.
Acknowledgements
Dr. Sotzing and Dr. Scola wish to thank the Institute of Materials
Science and the Polymer Program at the University of Connecticut
for their support. Dr. Thongyai and Dr. Praserthdam wish to thank
the Chulalongkorn University Dutsadi Phiphat Fund and MEKTEC
Manufacturing Corporation (Thailand) Ltd. for financial support of
this work.
Fig. 3. Overlaid TGAsof a) PEDOT, PANi, PPy with SPI1 and b) PEDOT, PANi, PPy with SPI2.
or addition of a secondary dopant; but PANi-SPAA2 exhibited its
highest value, 1.47 S/cm, when doped with DMF (0.1 wt.%). The
result of PPy systems showed similar trends to the PEDOT systems:
the conductivities were increased when doped with a secondary
substance and also were annealed for a short time. The highest
Appendix. Supplementary material
ꢁ1
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.polymer.2010.08.008.
value for PPy-SPI1 was 3.97 ꢂ 10 S/cm and the highest value for
ꢁ
1
PPy-SPI2 was 1.36 ꢂ 10
S/cm, which were doped with DMF
(
0.1 wt.%) and d-sorbitol (5 wt.%, respectively), and were both
annealed at 180 C for 10 min. The highest conductivities for all of
the various samples are summarized in Fig. 2.
ꢀ
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