Polyphosphazenes sulfonated

As mentioned earlier, a variety of membrane materials have been investigated for possible use in hydrogen/alr fuel cells and DMFCs, including sulfonated polyimides, sulfonated poly(arylene ether)s, sulfonated poly(ether ether ketone)s, and phosphoric acid-doped polybenzimidazole [5,321-331]. Many of these membrane materials suffer from poor oxidative stability, excessive swelling when wet and brittleness when dry, and only moderately high proton conductivity. Thus, none of the polymers has yet emerged as the preferred proton exchange membrane material for fuel cell 

3 1 General structure of polyphosphazenes. In most cases, Ri and R2 are aryloxy groups. 

22 Polyphosphazene synthesis scheme developed by AUcock (a) trimer synthesis, (b) ring-opening polymerization, and (c) macromolecular nucleophiUc substitution. 

23 Two possible cross-hnking routes (a) cationic growth via P—N=P hnk and (b) intermolecular condensation with formation of P—O—P cross-links. 

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Wycisk, R. and Pintauro, P. N. 1996. Sulfonated polyphosphazene ion-exchange membranes. Journal of Membrane Science 119 155-160. 

Andrianov, A. K., Marin, A., Chen, J., Sargent, J. and Corbett, N. 2004. Novel route to sulfonated polyphosphazenes Single-step synthesis using "noncova-lent protection" of sulfonic acid functionality. Macromolecules 37 4075 4080. 

Allcock s research led to the development of poly-phosphazene-based PEMs by his small molecule studies of the sulfonation of cyclic trimeric phosphazenes and the surface chemistry of polyphosphazene macromolecules. In a 1993 report, he described the sulfonation of aminophosphazenes with 1,3—propanesultone. While these specific materials are not necessarily ideal as PEMs, this study demonstrated a novel technique for creating sulfonated polyphosphazene materials that may provide more control over the sulfonated polymer product than wholesale sulfonation of a base polymer by a strong sulfonating agent. 

Allcock et al. also have investigated the use of phosphonated polyphosphazenes as potential membrane materials for use in direct methanol fuel cells (Figure A2) Membranes were found to have lEC values between 1.17 and 1.43 mequiv/g and proton conductivities between 10 and 10 S/cm. Methanol diffusion coefficients for these membranes were found to be at least 12 times lower than that for Nafion 117 and 6 times lower than that for a cross-linked sulfonated polyphosphazene membrane. 

Wycisk, R., Lee, J.K., and Pintauro, P.N., Sulfonated polyphosphazene-polybenzimid-azole membranes for DMFCs, J. Electrochem. Soc., 152, A892, 2005. 

R. Wycisk, P.N. Pintauro, Sulfonated polyphosphazene ion-exchange membranes, J. Membr. Sci., 1996, 119, 155 Q. Guo, P.N. Pintauro, Sulfonated and cross-linked polyphosphazene-based proton-exchange membranes, J. Membr. Sci., 1999, 154, 175. 

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... 

A. K. Rianov, a. Marin, ). Chen,. Sargent, N. Corbett, Novel Route to Sulfonated Polyphosphazenes Single-Step Synthesis Using Noncovalent ProtectionT of Sulfonic Acid Enmctional-ity. Macromolecules 37 (2004) 4075-4080. 

Wycisk R, Lee JK, Pintauro PN (2005) Sulfonated polyphosphazene-polybenzimidazole membranes for DMFCs. J Electrochem Soc 152 A892-A898... 

Pintauro PN, Wycisk R (2004) Sulfonated polyphosphazene membranes for direct methanol fuel cells . Phosphazenes 591. 

Fig. 4 Synthesis of sulfonated polyphosphazenes by a direct substitution of PD CP with a protected sulfonic acid nucleophile, and b postsulfonation using concentrated sulfuric acid...

Fig. 11 SEM micrographs of phase-separated sulfonated polyphosphazene blends a SPB3MPP-PVDF, b SPB3MPP-PAN, and c SPBPP-PBI...

Fig. 14 Proton conductivity versus water swelling correlation for three types of blended membranes with sulfonated polyphosphazene...

The latest patent application comes from researchers representing Toyota and Case Western Reserve University [53]. The invention describes the use of multiaromatic ring-sulfonated polyphosphazenes as fuel-cell electrode binders. 

Pintauro PN, Wycisk R (2004) Sulfonated polyphosphazene membranes for direct methanol fuel cells. In Gleria M, De Jaeger R (eds) Phosphazenes a worldwide Insight. Nova Science Publishers, New York, 25 591... 

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