Sulfonated polybenzimidazole

It is also possible to sulfonate PBI by direct treatment with sulfuric acid. A patent from Motorola Inc. [382] describes the sulfonation of PBI dissolved in concentrated sulfuric acid. Wet films of the so-obtained polymers have a conductivity 

3 Alkykulfonation of PBI by reaction with propane or butane sultone [369,371,372, 381]. 

Sulfonated tetraamine and the corresponding sulfonated polybenzimidazoles [387] were also synthesized, where a strong acid medium was used as a polymerization solvent, allowing for the preparation of high molecular weight sFBI. The membranes prepared from the sFBI display low water uptake, but low ionic conductivities were reported. The specihc acid-base interactions between benzimidazole rings and 

A sulfonated polybenzimidazole that has all the desired properties of conductivity and thermal stability to be used at 150-200 °C is sulfonated ABPBI prepared by direct sulfonation of a previously cast membrane, followed by phosphoric acid doping as detailed in Fig. 3.34. Sulfonation of ABPBI reduces the phosphoric acid uptake at low doping bath concentrations, but at high bath concentrations the sulfonated ABPBI absorbs more acid than the nonsulfonated ABPBI (Fig. 3.35), and the phosphoric acid uptake in these concentrated baths increases with the sulfonation degree (Fig. 3.36). As it could be expected, this higher doping level leads to an increase in conductivity as shown in Fig. 3.37 [382,396]. 

Pu and Liu have compared PBI and benzylsulfonated PBI, both doped with phosphoric acid, concerning their conductivity and methanol permeability, finding 

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Glipa, X. et al.. Synthesis and characterisation of sulfonated polybenzimidazole a highly conducting proton exchange polymer. Solid State Ionics, 97, 323, 1997. 

Rozifere, J. et al.. On the doping of sulfonated polybenzimidazole with strong bases. Solid State Ionics, 145, 61, 2001. 

Fig. 7 Chemical structures of some sulfonated polymers and a polyimide (A) sulfonated polyetheretherketone, PEEK, PSE (B) sulfonated polyphenylenesulfide, PPS (C) sulfonated polysulfone (D) poly(4,4 -biphenol) (4,4 -dichlorodiphenyl sulfone), BPSH-XX (XX is mol% of disulfdonated units) (E) sulfonated polybenzimidazole, PBI (F) polyimide.

Wanga Y, Chnng TS, Gruender M. 2012. Sulfonated polybenzimidazole membranes for pervaporation dehydration of acetic acid. J. Membr. Sci. 415-416 486-495. 

Sulfonated aromatic polymers have been widely studied as alternatives to Nafion due to potentially attractive mechanical properties, thermal and chemical stability, and commercial availability of the base aromatic polymers. Aromatic polymers studied in fuel cell apphcations include sulfonated poly(p-phenylene)s, sulfonated polysulfones, sulfonated poly(ether ether ke-tone)s (SPEEKs), sulfonated polyimides (SPIs), sulfonated polyphosphazenes, and sulfonated polybenzimidazoles. Representative chemical structures of sulfonated aromatic polymers are shown in Scheme 3. Aromatic polymers are readily sulfonated using concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or sulfur trioxide. Post-sulfonation reactions suffer from a lack of control over the degree and location of functionalization, and the... 

Sulfonated polybenzimidazoles have been prepared by polycondensation of sulfoterephthalic acid and disulfoisophthalic acid with 3,3 -diaminoben-zidine using high temperature solution polycondensation in PPA [150-153]. 

Pu H, Liu Q (2004) Methanol permeation and proton conductivity of polybenzimidazole and sulfonated polybenzimidazole. Polym Int 53 1512-1516... 

Feng S, Shang Y, Wang S, Xie X, Wang Y, Wang Y, et al. Novel method for the preparation of ionically crosslinked sulfonated poly(arylene ether sulfone)/polybenzimidazole composite membranes via in situ polymerization. J Membr Sci 2010 346(1) 105-12. 

Kim HJ, Lee JW, Lim TH, Nam SW, Hong SA, Oh IH et al. Partially sulfonated polybenzimidazole based polymer, method for preparing the same, mea for fuel cell using the polybenzimidazole based polymer and method for preparing the same. US patent 8 293 138, assigned to Korea Institute of Science and Technology, Seoul, KR 2012. 

Research by Bai et al. [12] reported CO2/N2 selectivity of 249 at the same experimental conditions and feed gas composition as Zou et al. [13], namely 100 °C and feed pressure of 30 psi for polymeric membranes using sulfonated polybenzimidazole (SPBl)-ethylenediamine (EDA) copolymer containing 30 % SPBI, 50 % polyethylenimine (PEI) (hxed amine carrier), and 20 % 2-aminoisobu-tyric acid-potassium salt (mobile amine carrier). In this case again, they had mobile and fixed amine carriers. 

Bai H, Ho WSW (2009) New carbon dioxide-selective membranes based on sulfonated polybenzimidazole (SPBI) copolymer matrix for fuel cell applications. Ind Eng Chem Res 48(5) 2344-2354... 

Glipa, X., Haddad, M.E., Jones, D.J. and Roziere, J. 1997. Synthesis and characterization of sulfonated polybenzimidazole A highly conducting proton exchange polymer. Sdid datej d 323-331. 

J. Jouanneau, R. Mercier, L. Gonon, G. Gebel, Synthesis of sulfonated polybenzimidazoles from functionalized monomers preparation of ionic conducting membranes. Macromolecules 40 (4) (2007) 983-990. 

W. Huanga, S.B. Qinga, J.T. Yang, D.Y. Yan, Preparation and characterization of soluble sulfonated polybenzimidazole for proton exchange membrane materials. Chin. J. Polym. Sci. 26 (2) (2008) 121-129. 

S. Qing, W. Huang, D. Yan, Synthesis and properties of soluble sulfonated polybenzimidazoles, React. Funct. Polym. 66 (2) (2006) 219-227. 

Staiti P, Lufrano F, Arico AS, Passalacqua E, Antonucci V (2001) Sulfonated polybenzimidazole membranes - preparation and physico-chemical characterization. J Membr Sci... 

Mader J (2010) Novel sulfonated polybenzimidazole derivatives for high temperature fuel cell applications. PhD Thesis, Rensselaer Polytechnic Institute, Troy, NY... 

Figure 1.15 Synthesis of sulfonated polybenzimidazole. Reproduced from [40] with permission from Elsevier. 

Polybenzimidazoles with pendent acidic groups sulfopropylated polybenzimidazole [31], sulfonated polybenzimidazole by the grafting of (4-bromomethyl)benzenesulfonate onto PBI [32], phosphonated fuUy aromatic polyethers containing pyridine building blocks [33], sidfraiated aromatic polyethers containing pyridine units [34], sulfonated polybenzimidazoles from sulfonated dicar-boxylic acid monomers [35-37]. 

Qing S, Huang W, Yan D (2005) Synthesis and characterization of thermally stable sulfonated polybenzimidazoles. Eur Polym J 41 1589-1595... 

Yang JS, Aili D, Li QF et al (2013) Covalently cross-linked sulfone polybenzimidazole membranes by poly (vinylbenzyl chloride) for fuel cell applications. ChemSusChem 6 275-282... 

Mader JA, Benicewicz BC (2010) Sulfonaled polybenzimidazoles for high temperature PEM fuel cells. Macnunolecules 43 6706-6715... 

Wang G, Xiao G, Yan D (2011) Synthesis and properties of soluble sulfonated polybenzimidazoles derived from asymmetric dicarboxylic acid monomers with sulfonate group as proton exchange membrane. J Membr Sci 369 388-396... 

Table 10.1 Acid content, sulfuric and phosphoric add, in sulfonated polybenzimidazoles. Reproduced frtnn [18] with permission of the American Chemical Society...

Qian W, Shang Y, Fang M et al (2012) Sulfonated polybenzimidazole/zirconium phosphate composite membranes for high temperature applications. Int J Hydrogen Energy 37 12919-12924... 

Xu HI, Chen KC, Guo XX et al (2007) S)mthesis of novel sulfonated polybenzimidazole and preparation of cross-linked membranes for fuel cell application. Polymer 48 5556-5564... 

Membrane prepared by blending sulfonated polybenzimidazole (PBI) with Nafion polymer showed a conductivity of 0.032 S cm The methanol permeability of the composite membrane was found to be 0.82 x 10 cm s as compared to Nafion, which is around 2.21 x 10 cm s [22]. Addressing the problem of methanol permeation, a composite membrane of Nafion with polyvinyl alcohol (PVA) for direct methanol fuel cell has been reported. It is concluded that at the weight ratio of 1 1 in PVA and Nafion, the thin film-coated Nafion membrane exhibited low methanol crossover, and the membrane protonic conductivity could be improved by the sulfonation treatment [23]. Recently, Zaidi et al. [24] prepared composite membranes of PFSA ionomer with boron phosphate and showed the conductivity of 6.2 X 10-2 S cm-i at 120°C. 

Several materials have been studied on the goal of producing cost-effective PFMs [55-62]. Some of these are PBI-based membranes, polysterene membranes, sulfonated polyimide, cross-Unked poly(vinyl alcohol), and phosphobenzene, sulfonated poly(aryl ether ketone) —based manbranes. Sulfonation of aromatic thermoplastics such as polyether sulfone, polybenzimidazole, polyimides, and poly(ether ether ketone) makes them proton conductive suitable for fuel cell... 

Because of good thermal and hydrolytic stability, excellent mechanical and chemical stability, low cost, and commercial availability of sulfonated aromatic hydrocarbon polymers, recent research has focused on the synthesis and development of sulfonated aromatic hydrocarbon polymers specifically for high-temperature PEMFCs. Typical examples include sulfonated poly(ether ether ketone) (SPEEK) or poly(ether ketone ketone) (SPEKK) [1,2], sulfonated poly(ether sulfone) (SPSE) [3], alkyl sulfonated polybenzimidazole (PBI), sulfonated naphthalenic polyinrides (sNPl) [4-6], sulfonated polyCphenylene sulfide) [7,8]. Both post- and pre-sulfona-tion methods have been used in the past. Other than the post-sulfonation modification of aromatic polymers, recently, efforts have been dedicated to direct polycondensation from sulfonic acid containing monomers to synthesize sulfonated polymers [9]. The latter approach, namely pre-sulfonation, is widely applied because of the ease of controlling sulfonation degree and deactivated sites in the arylene backbones, which further avoid side reactions such as decomposition and hydrolysis of polymers resulted from the post-sulfonation method. 

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