Synthesis and properties of novel sulfonated poly(phenylquinoxaline)s as proton exchange membranes

doi:10.1016/j.polymer.2009.10.033

Polymer

Volume 50, Issue 25, 27 November 2009, Pages 6001-6008

https://doi.org/10.1016/j.polymer.2009.10.033 Get rights and content

Abstract

Two series of sulfonated poly(phenylquinoxaline)s (SPPQ-x and SPPQ(O)-x, x refers to molar percentage of sulfonated tetraamine monomer) were first synthesized from a sulfonated tetraamine (4,4′-bis(3,4-diaminophenoxy)biphenyl-3.3′-disulfonic acid) and two aromatic bisbenzils (4-phenylglyoxalylbenzil and p,p′-oxydibenzil) in a mild condition. The structures of SPPQ-x and SPPQ(O)-x were characterized by IR and ¹H NMR spectra. The properties of these polymer films, such as water uptake, water swelling ratio, proton conductivity, thermal properties, methanol permeability, hydrolytic and oxidative stability were also investigated. The resulting polymers generally showed good solubility in DMAc and DMSO. Flexible and tough membranes with high mechanical strength were prepared. They show very high thermal, thermooxidative, hydrolytic stabilities and low methanol permeability. SPPQ-100 with the IEC value (2.41 mmol/g) displays the conductivity of 0.1 S/cm and a swelling ratio of 7.3% at 100 °C. The low swelling was attributed to the high rigid of polymer backbones and the strong intermolecular interaction between the basic nitrogen atoms of quinoxaline units and sulfonic acid groups. Moreover, we found that the conductivities of SPPQ(O)-x membranes were higher than SPPQ-x membranes at the similar IEC value. The highest conductivity of 0.2 S/cm was obtained for SPPQ(O)-100 at 140 °C. A combination of excellent dimensional and hydrolytic stabilities indicated that the SPPQ ionomers were good candidate materials for proton exchange membrane in fuel cell applications.

Graphical abstract

Introduction

Ion-conducting polymers are of interest for a variety of applications, such as sensors, actuators, batteries, and ion exchange membranes or resins. Particularly, recent progress in the area of polymer electrolyte membrane fuel cells (PEMFCs) has stimulated considerable interest in proton conductive polymer membranes [1]. Polymer electrolyte membrane (PEM) plays a key role in a PEFC system, namely to provide a barrier to the fuel gas cross-leaks between the electrodes and to transfer protons from the anode to the cathodes. Currently, perfluorinated ionomers such as Nafion are the state of the art materials because of their excellent chemical stability and high proton conductivity. However, high cost, high fuel and oxygen crossover and lower operation temperature limit their wide application. In the past decade, a variety of proton conductive materials, especially the nonfluorinated aromatic hydrocarbon ionomers, have been proposed as alternative membranes [2]. Although each of them has its own advantages, most of them have failed to meet the requirements of high conductivity and durability under fuel cell operating conditions. The perfluorinated ionomers still stand as the state-of-the-art membranes [3].

One of the key issues to be emphasized on nonfluorinated aromatic ionomers is their poor hydrolytic stability or the balance between conductivity and dimensional stability in fuel cell operating conditions. To make hydrocarbon ionomers less susceptible to water swelling or hydrolysis, the selection of a suitable chemically and mechanically stable aromatic polymer as a base skeleton is very important. Poly(phenylquinoxaline)s (PPQs) are high performance thermoplastics well known for their excellent thermal and chemical stability and widely used in microelectronics and aerospace applications [4]. These polymers have also been shown to possess excellent thermohydrolytic stability and good dimensional stability over a wide temperature range [5], which are required properties for PEMs. Zhang et al. [6] first reported the preparation of conducting poly(phenylquinoxalines) films through the electrolysis of PPQ solution with corresponding supporting electrolytes under controlled potential. The conductivity of these PPQ films varies from 10⁻⁷ to 10⁻¹² S/cm depending on dopant anions in electrolytes. Kopitzke et al. [7] has successfully synthesized sulfonated poly(phenylquinoxaline) through the postsulfonation method and reported that the sample with the highest water uptake had a room temperature conductivity of 9.8 × 10⁻² S/cm. However, postsulfonation reactions are usually restricted due to their lack of precise control over the degree and location of sulfonic groups, the possibility of side reactions, or degradation of the polymer backbone [8].

In this article, we first report the synthesis of sulfonated poly(phenylquinoxaline)s by the direct copolymerization method using the corresponding monomers 4,4′-bis(3,4-diaminophenoxy)biphenyl-3,3′-disulfonic acid, 4,4′-bis(3,4-diaminophenoxy)biphenyl and two aromatic bisbenzils (4-(phenylglyoxalyl)benzil and p,p′-oxydibenzil). The properties of these novel sulfonated copolymer films, such as water uptake, water swelling ratio, proton conductivity, thermal properties, methanol permeability, hydrolytic and oxidative stability were also investigated.

Section snippets

Materials

4-(Phenylglyoxalyl)benzil (PGBZ) was synthesized according to the literature [9]. p,p′-oxydibenzil (ODB) was synthesized according to the literature [10]. 4,4′-Bis(3,4-diaminophenoxy)biphenyl-3.3′-disulfonic acid (BDAPBDS) and 4,4′-bis(3,4-diaminophenoxy)biphenyl (BDAPB) were synthesized according to the literature [11]. Triethylamine and m-cresol were distilled under reduced pressure. All other regents were used as received without further purification.

Polymer synthesis and membrane preparation

SPPQ-100 (100 refers to molar percentage

Synthesis and characterization of polymers

The preparation of SPPQ and SPPQ(O) copolymers was carried out through one-pot polymerization method in m-cresol as shown in Scheme 1. TEA was used to liberate the protonated amino groups of sulfonated tetraamine for polymerization with PGBZ or ODB. The degree of sulfonation (DS) of the copolymer was readily controlled through the monomer feed ratios of sulfonated tetraamine to non-sulfonated tetraamine, so that a series of copolymers with different IEC values could be obtained. The copolymers

Conclusions

A series of sulfonated poly(phenylquinoxaline) copolymers were successfully synthesized from novel sulfonated tetraamine, unsulfonated tetraamine and 4-phenylglyoxalylbenzil (or p,p′-oxydibenzil) in a mild condition. The copolymer membranes prepared by a solution casting method showed very high thermal, thermooxidative, hydrolytic stabilities and low methanol permeability. They also displayed good water swelling resistance because of the formation of acid-base complex between the N atoms of

Acknowledgements

We thank the National Basic Research Program of China (No. 2009CB623401), the National Science Foundation of China (No. 50673087 and 50825303) and the Development of Scientific and Technoloical Project of Jilin Province (No. 20080620) for the financial support.

References (24)

J. Roziere et al.
Solid State Ionics
(2001)
D.S. Kim et al.
J Membr Sci
(2006)
Z.W. Bai et al.
Polymer
(2007)
S.L. Zhong et al.
J Membr Sci
(2006)
Y.X. Li et al.
Polymer
(2006)
L. Wang et al.
J Membr Sci
(2006)
K. Miyatate et al.
J Am Chem Soc
(2007)
B. Lafitte et al.
Adv Funct Mater
(2007)
N. Asano et al.
J Am Chem Soc
(2006)
T. Fang
Macromolecules
(1991)

J.L. Hedrick et al.

Macromolecules

(1990)

C. Zhang et al.

Polymer

(1991)

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Coupling-type sulfonated poly(phenylquinoxaline) (c-SPPQ) bearing both side chain and main chain sulfonic acid groups were synthesized through the post-sulfonation process. The proton exchange membranes prepared with c-SPPQ showed good performance, such as low methanol permeability, high methanol tolerance and good mechanical properties due to the acid-base interaction between the sulfonic acid and phenylquinoxaline groups. The dimensional change of c-SPPQ-3 in the length direction was 33% at 30 °C in 45 wt% methanol solution, demonstrating the stability of membrane electrode assembly against shearing force. In contrast, NR212experienced significant swelling. The methanol flux of c-SPPQ-3 was 45 mg cm⁻² h⁻¹ for at 30 °C with a methonal concentration of 10 wt%. This was almost 10 times lower than that of NR212. With a 20 wt% methanol feed concentration at 75 °C, the maximum power density of c-SPPQ-3 was 88 mW cm⁻², 1.8 times higher than that for NR212 (48 mW cm⁻²). This was attributed to the reasonably high proton conductivity and low methanol permeability of c-SPPQ-3. When the methanol feed concentration was further increased to 50 wt%, the maximum power density of c-SPPQ-3 slightly decreased to 60 mW cm⁻², while that of NR212 was negligible. With such superior performance, c-SPPQ shows excellent promise for meeting the requirements of direct methanol fuel cells.
Block copoly(phenylquinoxaline)s as potential ionomers for proton exchange membranes
2023, Polymer
Poly(phenylquinoxaline)s are a family of aromatic condensation polymers known for their outstanding thermal and chemical stability. Based on this polymer class new sulfonated block copoly(phenylquinoxaline)s with different hydrophobic segments have been developed. The block copolymers were synthesized via polycondensation reactions between 3,3′,4,4′-tetraaminodiphenylether and two different tetraketones: tetrafluorphenylbis-phenylethandion and phenylbisphenylethandion. Block copoly(phenylquinoxaline)s up to a molecular weight M_n of 29.3 kg mol⁻¹ were obtained. The sulfonations of these block copolymers were carried out in a mixture of concentrated sulfuric acid and oleum (4:1) leading to ion exchange capacities of 1.77–2.36 mmol g⁻¹. Flexible films of sulfonated block copoly(phenylquinoxaline)s were realized by doctor blading of solutions in N’N-dimethylacetamide (DMAC) or N-ethyl-2-pyrrolidone (NEP). The resulting membranes achieved proton conductivities in the range of 48–110 mS cm⁻¹. Additionally, water uptake and dimensional stability were determined and presented.
Synthesis, curing kinetics and thermal properties of two novel quinoxaline-based mono- and bismaleimides
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Citation Excerpt :
Zhang et al. prepared a series of ether-bridged fluorinated PPQs (PEPPQ), the Tg values of PEPPQ were ranged from 260 to 290 °C, and the polymers’ char yield values (Yc at 700 °C) reached up to 75% [21]. Gong et al. reported two types of sulfonated PPQs (SPPQs), the results revealed that the main chain of phenylquinoxaline was cleaved around 530 °C, and the SPPQs showed fairly good oxidative stability compared to the recorded values for poly(arylene ether)s [22]. Wang et al. patented a series of preparation methods for quinoxaline-containing benzoxazine [23].
Two novel quinoxaline-based maleimide monomers, 2,3-diphenyl-6-maleimido-quinoxaline (MQMI) and 2,3-di(2-maleimido)phenyl-quinoxaline (BQMI), were successfully synthesized and characterized. Their structure was confirmed by ¹H nuclear magnetic resonance (¹HNMR) and Fourier transforms infrared (FTIR). The curing behavior was investigated by the rheological method and Differential scanning calorimetry (DSC). Starink method was used for the curing kinetics analysis of MQMI and BQMI monomers. The curing temperature and the apparent activation energy of BQMI were lower than that of MQMI, which indicated that the maleimide group location could affect its curing behavior. The thermal stabilities of the cured quinoxaline-based maleimide resins were detected by Thermogravimetric analysis (TGA), which implied that their decomposition temperatures were comparable with Poly(4,4’-bismaleimido diphenylmethane) (PBMDPM). However, the char yields (Y_c) of PMQMI and PBQMI reached 54.1% and 57.3%, respectively, which were much higher than recorded values of PBMDPM.
Novel aminated cellulose acetate membranes for direct methanol fuel cells (DMFCs)
2017, International Journal of Electrochemical Science
Currently, enhancing the mechanical properties and decreasing methanol permeability is the major challenge for the polyelectrolyte membranes for the direct methanol fuel cells (DMFCs). In this study, novel aminated proton exchange membrane based on cellulose acetate (CA) for DMFC were prepared via activation process using epichlorohydrin (ECH) afterward amination reaction using ethylene diamine (EDA). The structure of the aminated cellulose acetate membranes (AMCA) were investigated by a Fourier transform infrared spectroscopy, Scanning electron microscopy, Thermogravimetric analysis. The adsorption of the AMCA membrane of water and methanol solution was also characterized. Additionally, the AMCA membranes were investigated as a function of a molar ratio of EDA concerning ion exchange capacity (IEC), dimensional stability, thickness change, thermal oxidation stability, and methanol permeability in detail. Results revealed that the modified CA membranes have excellent dimensional stability, admirable physicomechanical properties (32.13 N) and low methanol permeability (4.54*10-17 cm2/S) compared to 1.14*10-9 cm2/S for commercial Nafion®117 membranes. Furthermore, the membrane performance with various contents of EDA showed a vast improvement compared to Nafion®117. In conclusion, the obtained series of AMCA membranes offering the possibilities to reduce the DMFC membrane cost considerably while keeping high performance. These results suggested that these membranes are quite attractive candidates as an innovative polymeric electrolyte material for DMFCs applications.
Proton exchange membranes derived from sulfonated polybenzothiazoles containing naphthalene units
2017, Journal of Membrane Science
Sulfonated polybenzothiazoles were synthesized by polycondensation of 6-sulfonate-1,4-naphthalene dicarboxylic acid, 2,5-diamino-1,4-benzenedithiol dihydrochloride and either 1,4-naphthalene dicarboxylic acid or 2,2-bis(4-carboxyphenyl) hexafluoropropane. The two series are denoted sPBT-NA and sPBT-6F, respectively. While the sPBT-NA series are insoluble in common solvents, the sPBT-6F series are soluble due to the incorporation of hexafluoroisopropylidene moieties, which impart more chain flexibility rather than disrupting the regular packing of the polymer main chain. The sPBT-6F series exhibited high proton conductivity, high thermal and oxidative stability, good mechanical properties and appropriate water uptake and dimensional swelling behavior. For example, the proton conductivity of sPBT-6F90 was much higher than that of Nafion 117, and the proton conductivity of sPBT-6F80, sPBT-6F85 and sPBT-6F95 is also as high as that of Nafion 117. The combined properties of the present sulfonated polybenzothiazoles are commendable for proton exchange membranes.
Interpenetrating network-forming sulfonated poly(vinyl alcohol) proton exchange membranes for direct methanol fuel cell applications
2011, International Journal of Hydrogen Energy
Citation Excerpt :
For these reasons, much research is being directed towards obtaining membranes that overcome these problems. Proton exchange membranes such as those based on sulfonated poly(aryl ether sulfone) [7–11], sulfonated poly(ether ketone) [12–15], sulfonated polyimide [16–20], and sulfonated polybenzimidazole [21–24] have been proposed as alternative membrane materials for PEMFCs. The introduction of sulfonic acid groups is achieved either by direct sulfonation of the polymers or by polymerization of sulfonated monomers.
Poly (vinyl alcohol) was sulfonated and subsequently cross-linked by a thermal curing reaction with dual cross-linkers to prepare membranes for direct methanol fuel cells. Sulfonated poly (vinyl) alcohol (SPVA) with a high degree of sulfonation was synthesized from 4-Formylbenzene-1,3-disulfonic acid disodium salt hydrate via an acetalization reaction with PVA. Various masses of the cross-linking agents 1,3-bis(3-glycidyloxypropyl) tetramethyldisiloxane and 4,4′-oxydiphthalic anhydride were polymerized with SPVA to facilitate manipulation of the properties of the membranes. Notably, the SPVA3 showed excellent proton conductivity (cf. $σ$ = 0.218 S cm⁻¹ at 70 °C and Nafion 117 = 0.127 S cm⁻¹), and low methanol permeability (around one half of that Nafion 117). These results suggest that the cross-linked SPVA membranes hold promise as potential proton exchange membranes and given their high proton conductivity and low methanol permeability they may offer advantages when used in direct methanol fuel cells (DMFCs) applications.

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Synthesis and properties of novel sulfonated poly(phenylquinoxaline)s as proton exchange membranes

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Polymer synthesis and membrane preparation

Synthesis and characterization of polymers

Conclusions

Acknowledgements

Solid State Ionics

J Membr Sci

Polymer

J Membr Sci

Polymer

J Membr Sci

J Am Chem Soc

Adv Funct Mater

J Am Chem Soc

Macromolecules

Macromolecules

Polymer