Methacrylate-terminated Poly(3,4-Ethylenedioxythiophene) (PEDOT) polymers with controlled degree of polymerization were successfully prepared by direct oxidative polycondensation between Ethylenedioxythiophene (EDOT) and a cross-linkable methacrylate end-capper monomer, obtained via Friedel Crafts acylation starting from EDOT and Methacryloyl chloride. The new polymer was synthesized in order to overcome the well-known technical problems of PEDOT, i.e. difficult processability and patterning, due to its poor solubility in common organic and inorganic solvents. The chemical structure and the degree of polymerization of the end-capped polymers were determined by 1H NMR spectra. A new synthesis of Methacrylate end-capped PEDOT with controlled degree of polymerization, soluble in common organic and chlorinated solvents and with improved conductivity, 210 S/cm, was performed. This method includes: direct oxidative polycondensation of 3,4-Ethylenedioxythiophene (EDOT) in the presence of a cross-linkable end-capper, i.e. Methacrylate end-capped EDOT prepared via Friedel Crafts acylation with Methacryloyl chloride and oxidant species, i.e. ferric sulfate. Furthermore, the oxidative polycondensation of EDOT monomer and Methacrylate end-capped EDOT in the presence of Sulfonated Polyethersulfone (SPES)- characterized by different degree of Sulfonation (DS)- as dopant agent was performed, leading to functional end-capped conducting PEDOT, easy to process and pattern, with conductivity of 210 S/cm, 50 S/cm higher than the one of commercial PEDOT

H. Farina

M.A. Ortenzi

V. Sabatini

AIR Universita degli studi di Milano

Functional End-Capped Conducting Poly (3,4-
Ethylenedioxythiophene) 
V. Sabatini
a,b
, H. Farina
a,b
, and Marco A. Ortenzi
a,b
 
a 
Department of Chemistry, University of Milan, Via Golgi 19 – 20133 Milan, Italy 
b 
CRC Polymeric Materials (LaMPo), 
 
Department of Chemistry, University of Milan, Via Golgi 19 – 20133 Milan, 
Italy 
Abstract. Methacrylate-terminated Poly(3,4-Ethylenedioxythiophene) (PEDOT) polymers with controlled 
degree of polymerization were successfully prepared by direct oxidative polycondensation between 
Ethylenedioxythiophene (EDOT) and a cross-linkable methacrylate end-capper monomer, obtained via Friedel 
Crafts acylation starting from EDOT and Methacryloyl chloride. The new polymer was synthesized in order to 
overcome the well-known technical problems of PEDOT, i.e. difficult processability and patterning, due to its poor 
solubility in common organic and inorganic solvents. The chemical structure and the degree of polymerization of the 
end-capped polymers were determined by 
1
H NMR spectra. A new synthesis of Methacrylate end-capped PEDOT 
with controlled degree of polymerization, soluble in common organic and chlorinated solvents and with improved 
conductivity, 210 S/cm, was performed. This method includes: direct oxidative polycondensation of 3,4-
Ethylenedioxythiophene (EDOT) in the presence of a cross-linkable end-capper, i.e. Methacrylate end-capped 
EDOT prepared via Friedel Crafts acylation with Methacryloyl chloride and oxidant species, i.e. ferric sulfate. 
Furthermore, the oxidative polycondensation of EDOT monomer and Methacrylate end-capped EDOT in the 
presence of Sulfonated Polyethersulfone (SPES)- characterized by different degree of Sulfonation (DS)- as dopant 
agent was performed, leading to functional end-capped conducting PEDOT, easy to process and pattern, with 
conductivity of 210 S/cm, 50 S/cm higher than the one of commercial PEDOT. 
Keywords: conducting polymer, PEDOT, oxidative polycondensation, end-capping monomer, Sulfonated Polyethersulfone. 
PACS: 82.35.Cd 
INTRODUCTION 
Polythiophene and its derivates have been at the center of considerable scientific interest for their attractive 
chemical, physical and conductive features for the last years [1]. Among the derivates of Polythiophene, Poly (3,4-
Ethylenedioxythiophene) (PEDOT) is one of the most successful conducting polymers due to its low bandgap, 
excellent environmental stability, high electrical conductivity and transparency when in the form of thin oxidized 
films [2]. 
Since the first synthesis of PEDOT in 1989 [3], several studies on this polymer have been carried out [4] and 
many applications have been reported for solid electrolytic capacitors, anti-electrostatic agents, transparent 
electrodes in light emitting diodes, and under layers for the metallization of printed circuit boards [5]. 
Numerous researches have been made on the synthesis of PEDOT by electrochemical [6] and chemical oxidative 
[7] polymerization of 3,4-Ethylenedioxythiophene (EDOT), that has been recognized as more suitable for mass 
production than other possible monomers [8]. In 2005, Lei and others [9] suggested a new technique for PEDOT 
polymerization: the synthesis is performed by high-concentration emulsion polymerization of EDOT in the presence 
of sodium salt of 2-naphthalenesulfonic acid as dopant agent and ferric sulfate as oxidant. The conductivity of 
PEDOT obtained using this polymerization resulted to be 160 S/cm, an excellent value for an organic conducting 
polymer. Despite the excellent conducting properties, an important drawback of PEDOT is its poor solubility in the 
common organic and inorganic solvents, which is only partially circumvented in PEDOT-Sulfonated Polystyrene 
(SPS) composites [10]. 
In the present work we have developed a synthetic route able to enhance PEDOT solubility and conductivity. 
Methacrylate-terminated PEDOT polymers with controlled degree of polymerization (n), ranging from 4 to 50, were 
successfully synthesized via oxidative polymerization of EDOT and cross-linkable Methacrylate end-capped EDOT, 
with ferric sulfate as oxidant. EDOT end-capping monomer was prepared through Friedel Crafts acylation starting 
from EDOT and Methacryloyl Chloride. The chemical structure and the degree of polymerization of the end-capped 
polymers were determined by 
1
H NMR spectroscopy. The polymers synthesized have excellent solubility in several 
organic (dimethylacetamide, dimethylformamide and toluene) and chlorinated solvents (methylene chloride and 
chloroform). Furthermore, the use of cross-linkable end-caps makes EDOT-based polymers soluble in organic and 
chlorinated solvents in reversible conditions; the cross-linking of PEDOT film is then possible after UV exposure.  
In order to improve PEDOT conductive properties, the dopant agents based on sulfonic groups commonly used 
with PEDOT are 2-Naphthalenesulfonic acid, para toluene sulfonic acid or others [11]. Besides these molecules, also 
Sulfonated Polyethersulfone (SPES), obtained as reported in our previous work [12], can be used as dopant agent 
thanks to the possibility to modulate the moieties of sulfonic groups in the polymeric chains. 
In this work, SPESs with different degree of sulfonation (DS) were synthesized via polycondensation using a 
sulfonated comonomer, 2,5-Dihydroxybenzene-1-sulfonate potassium salt. The oxidative polymerization of EDOT 
and functional end-capped EDOT monomers with ferric sulfate as oxidant and SPES as dopant was performed; it 
was found that PEDOT conductive features increase as DS of SPES increases reaching 210 S/cm, a value far higher 
than the one of commercial PEDOT (160 S/cm). 
EXPERIMENTAL 
3,4-Ethylenedioxythiophene (EDOT, >97%), Methacryloyl Chloride (≥97%), ferric sulfate (Fe2(SO4)3.xH2O, 
>97%), acetone (≥99.9%), Dimethylacetamide (DMAc, ≥99.5%), toluene (99.8% anhydrous), Dimethylformamide 
(DMF, ≥99.5%), Methylene chloride (CH2Cl2, ≥99.5), Chloroform (CHCl3, ≥99.5%) and Dimethyl sulfoxide-d6 
(DMSO-d6, 99.96 atom % D) were supplied by Sigma Aldrich and used without further purification.  
Sulfonated Polyethersulfone (SPES) with three different degree of sulfonation (DS) -0.5, 0.75, 1 meq SO3
-
*g
-1
- 
was synthesized as reported in previous work [12]. 
DMAc suspension of SPES with 0.5 meq SO3
-
*g
-1
 (1.143g in 5ml) was mixed with EDOT (0.50ml, 0.665g) and 
methacrylate end-capped EDOT (0.555g) on a magnetic stirrer, at room temperature and under air atmosphere. 
DMAc solution of ferric sulfate (1.638g in 5ml) was added drop-wise by to the suspension. The reaction mixture 
was stirred for 5 h at room temperature.  
The polymerization reaction was repeated changing both SPES DS -0.75, 1 (SO3
-
*g
-1
) - and the reaction time: 10 
h, 15 h, 20 h and 24 h. The dark-blue deposition obtained was collected by centrifugation with Eppendorf centrifuge, 
8000rpm, washed with acetone and dried under vacuum at 30°C and 4 mbar overnight. 
The structures of end-capped EDOT monomer and PEDOT copolymers and the degree of polymerization of the 
resultant polymers were determined by 
1
H NMR spectra, collected at 25°C with a BRUKER 400 MHz spectrometer. 
Samples for the analyses were prepared dissolving 10-15 mg of polymer in 1 ml of DMSO-d6. Electrical 
conductivity of PEDOT was measured employing Metrohm conductivity meter. 
RESULTS and DISCUSSION 
Methacrylate-terminated PEDOT polymers with controlled degree of polymerization (n), 4≤ n ≤ 50, were 
successfully synthesized via oxidative polymerization using ferric sulfate as oxidant species. The degree of 
polymerization was controlled through the modulation of reaction time -5 h to have n=4, 10 h to get n=20, 15 h to 
have n=30, 20 h for n=45 and 24 h for n=50- and determined by 
1
H NMR spectra.  
Figure 1 shows the synthetic route for preparing Methacrylate end-capped PEDOT. The end-capper used in this 
work is a Methacrylate end-capped EDOT monomer, synthesized via Friedel Crafts acylation between EDOT and 
Methacryloyl Chloride, the latter characterized by the presence of a flexible chain and vinyl cross-linkable group. 
The use of cross-linkable end-capped monomers can be an effective way to improve PEDOT processability and 
patterning: in fact, adding flexible chains promotes the solubility of PEDOT in the common organic and inorganic 
solvents in reversible conditions and only after UV light exposure, thanks to the presence of cross linkable 
terminations, it is possible to obtain a stable crosslinked polymeric film. 
 
 
 
FIGURE 1.  Synthetic route for Methacrylate end-capped PEDOT. 
 
The polymers obtained are characterized by excellent solubility in many organic -dimethylacetamide, 
dimethylformamide and toluene- and chlorinated solvents -methylene chloride and chloroform- for every degree of 
polymerization considered.  
A series of SPES copolymers with three different DS -0.5-0.75-1.0 meq SO3
-
*g
-1
- were successfully synthesized 
by the aromatic nucleophilic substitution reaction of 4,4’-difluorodiphenylsulfone, 4,4’–dihydroxydiphenyl and a 
sulfonated comonomer, 2,5-dihydroxybenzene-1-sulfonate potassium salt: these SPES were used as PEDOT dopant 
agents, thanks to the charge separation deriving from the sulfonated comonomer (Fig. 2). The study related to 
PEDOT: SPES interaction mechanism is now in progress and will be discussed in subsequent works. 
 
 
 
FIGURE 2.  SPES as dopant agent for Methacrylate end-capped PEDOT. 
 
The conductive properties of Methacrylate end-capped PEDOT were studied both in function of different 
PEDOT degrees of polymerization (SPES with DS of 1 meq SO3
-
*g
-1
 was used as dopant agent), Fig. 3 (a), and in 
function of the DS of SPES employed as dopant agents, using Methacrylate end-capped PEDOT with degree of 
polymerization of 50n, Fig. 3 (b). 
 
FIGURE 3.  (a) PEDOT conductivity vs. PEDOT degree of polymerization (DS of SPES = 1 meq SO3
-*g-1); (b) PEDOT 
conductivity vs. SPES DS (PEDOT degree of polymerization = 50). 
 
Fig. 3 (a) shows that PEDOT conductivity with SPES having DS of 1 meq SO3
-
*g
-1 
increases as PEDOT degree 
of polymerization gets higher: 10 S/cm in the case of 4n, 75 S/cm for 20n, 130 S/cm for 30n, 195 S/cm for 45n and, 
at last, 210 S/cm in the case of PEDOT characterized by 50n. This last value is 50 S/cm higher than the one of 
commercial PEDOT. Fig 3b confirms that the higher the DS of SPES used as dopant agent, the higher the 
conductivity. The results obtained suggest that Methacrylate end-capped PEDOT conductive properties are straightly 
dependent by both PEDOT degree of polymerization and SPES DS. 
CONCLUSIONS 
A new synthesis of Methacrylate end-capped Poly (3,4-Ethylenedioxythiophene) (PEDOT) with controlled 
degree of polymerization, soluble in common organic and chlorinated solvents and with improved conductivity, 210 
S/cm, was performed. This method includes: direct oxidative polycondensation of 3,4-Ethylenedioxythiophene 
(EDOT) in the presence of a cross-linkable end-capper, i.e. Methacrylate end-capped EDOT prepared via Friedel 
Crafts acylation with Methacryloyl chloride, oxidant species and dopant agent, Sulfonated Polyethersulfone (SPES), 
characterized by different degree of sulfonation (DS).  
It was found that the use of cross-linkable end-caps renders PEDOT soluble in the common organic and 
chlorinated solvents and only after UV exposure it is possible to obtain a stable crosslinked PEDOT film. 
Furthermore PEDOT conductive features increase as both PEDOT degree of polymerization increases and SPES DS 
increases. 
ACKNOWLEDGMENTS 
The authors wish to thank and express their gratitude to Professor Giuseppe Di Silvestro for stimulating 
discussion and scientific projects. 
REFERENCES 
1. Q. Xu, T. Song, W. Cui, Y. Liu, W. Lee, and B. Sun, ACS Appl. Mat. Inter 7, 3272-3279, (2015). 
2. W. M. Sears, C. D. MacKinnon and T. M. Kraft, Synth. Met 161, 1566-1574, (2011). 
3. J. Roncali, Chem. Rev 92, 711-738, (1992). 
4. Z. Liu, K. Parvez, R. Li, R. Dong, X. Feng and K. Mullen, Adv. Mat 27, 669-675, (2015). 
5. M. R. Lenz, N. M. Kroneneberg, F. Würthner and K. Meerholz, Org. Elec 21, 171-176, (2015). 
6. M. Takayanagi, T. Gejo and I. Hanazaki, J. Phys. Chem 98, 12893-12898, (1994). 
7. O. Pyshkina, A. Kubarkov and V. Sergeyev, Mat. Sci. Appl. Chem 21, 51-53, (2010). 
8.  Z. U. Khan, O. Bubnova, M. J. Jafari, R. Brooke, X. Liu, R. Gabrielsson and X. Crispin, J. Mat. Chem 3, 10616-10623, 
(2015).  
9. Y. Lei, H. Oohata, S. Kuroda, S. Sasaki and T. Yamamoto, Synth. Met 149, 211-217 (2005). 
10. D. Yoo, J. Kim, S. H. Lee, W. Cho, H. H. Choi, F. S. Kim and J. H. Kim, J. Mat. Chem A 3, 6526-6533, (2015). 
11. J. E. McCarthy, C. A. Hanley, L. J. Brennan, V. G. Lambertini and Y. K. Gun’ko, J. Mat. Chem C, 2, 764-770, (2014). 
12. G. Soliveri, V. Sabatini, H. Farina, M. A. Ortenzi, D. Meroni and A. Colombo, J. Col. Surf. A 483, 285-291 (2015). 


Functional end-capped conducting poly (3,4-ethylenedioxythiophene)

Marco A. Ortenzi

Crossref

https://air.unimi.it/retrieve/handle/2434/385903/591804/Sabatini_Farina_Ortenzi.pdf

Functional end-capped conducting poly (3,4-ethylenedioxythiophene)

Abstract

Similar works

Full text

Available Versions

AIR Universita degli studi di Milano

Crossref