Sulfonated poly phosphazene

SPSs), sulfonated polyimides (SPIs), sulfonated polyfphenylene) s (SPPs), sulfonated poly(arylene)-type polymers (SPAs), and sulfonated poly(phosphazene)s (SPPtis). " They contain hydro-phobic blocks (hydrocarbon backbone) and hydrophilic blocks (containing sulfonic acid groups). Sulfonic acid groups, which are commonly employed as hydrophilic functional groups, form well-defined nanosized channels for proton conduction. 

Fig. 9 Conductivity in dependence of water content, a-----Nafion 112, — a modified poly(perfiuoro sulfonic acid), and---S-PTES [3] b various hydrocarbon polymers sulfonated poly(phosphazene) [1,192], -- benzylsulfonated PBI (80% sul-...

Tang, H., Pintauro, P. N., Guo, Q. and O Connor, S. 1999. Polyphosphazene membranes. ni. Solid-state characterization and properties of sulfonated poly[bis(3-methylphenoxy)phosphazene]. Journal of Applied Polymer Science 71 387-399. 

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. 

H. Tang, P.N. Pintauro, Q. Guo and S. O Connor, Polyphosphazene membranes. III. Solid-state characterization and properties of sulfonated poly[bis(methylphenoxy)-phosphazene], J. Appl. Polym. Sci., 1999, 71, 389-399. 

Herrero and Acosta (80) investigated the microstmcture of poly(ethylene oxide)-poly[(octafluoropentoxy)(trifluoroethoxy)phosphazene] blends. Limited miscibility of both components was inferred, based on the observed shift of the components glass-transition temperatures. Wycisk and co-workers (81) prepared membranes from blends of sulfonated poly[bis(3-methylphenoxy)phosphazene] with polyimides, polyacrylonitrile, and Kynar FLEX PVDF. Morphology, electrochemical performance, and methanol permeabilities of the membranes were then evaluated as part of a program to investigate such blends in direct methanol fuel cells. The polymers were immiscible and a domain-type structure was observed. The best compatibility resulted when the tetrabutylammonium or sodium salt of the polyphosphazene was used (82). 

Tang et al. [30] and Guo et al. [31] found that sulfonated poly[bis(3-methylphenoxy)phosphazene] (denoted as SPB3MPP) (Fig. 7b) offered an attractive combination of good proton conductivity, crosslinkability and low methanol permeability features especially important for direct methanol fuel-cell membranes. UV-crosslinked membranes prepared from SPB3MPP of lEC 1.4 mmol/g exhibited a methanol diffusion coefficient on the order of 1.0 X lO cm /s, which was significantly smaller than that in a Nation... 

Fig. 7 Example structures of polyphosphazene sulfonic acids a sulfonated poly[(me-thylphenoxy)(phenoxy)phosphazene], b sulfonated poly[bis(3-methylphenoxy)(phenoxy)-phosphazene], c sulfonated poly[bis(phenoxy)phosphazene] and d sulfonated poly[bis(2-phenoxyethoxylphosphazene]...

An interesting polyphosphazene derivative, sulfonated poly[bis(2-phen-oxyethoxy)phosphazene], was reported by Paulsdorf et al. [35] (Fig. 7d). Living cationic polymerization of CI3P = NSi(CH3)3 monomer was used to obtain PDCP, which was reacted with 2-phenoxyethanol. The aryl substituents... 

Fig. 13 DSC thermograms of four blends of sulfonated poly[bis(phenoxy)phosphazene] with PBI (SPBPP-PBI), imsulfonated poly[bis(phenoxy)phosphazene] (PBPP) and pure sulfonated poly[bis(phenoxy)phosphazene] (SPBPP) with an IEC= 1.4mmol/g. The two vertical broken lines depict the glass transitions of the PBPP (-3 °C) and SPBPP (59°)...

Fig. 16 Direct methanol fuel-cell performance curves with blended membranes composed of PVDF and either sulfonated poly[(3-methylphenoxy)(4-ethylphenoxy)phosphazene] (SP3MP4EPP) or sulfonated poly[(4-ethylphenoxy)(phenoxy)phosphazene] (SP4EPPP). 1.0 M methanol feed, 60 °C, air at ambient pressure and 500 seem. Cross denotes the methanol crossover flux (mol/cm min) at open circuit, relative to that in Nafion 117...

Fig. 19 The effect of methanol feed concentration on the maximum power density in a direct methanol fuel cell, for Nafion 117 and two PBI-doped sulfonated poly[bis(phen-oxy)phosphazene] membranes...

Poiyphosphazene Biends Blends of sulfonated polyphosphazene, for example, sulfonated poly[bis(3-methylphenoxy)phosphazene] or poly[(bisphenoxy)phosphazene] (see Fig. 29.14) with either an inert organic polymer such as poly(vinylidene fluoride) (Pintauro and Wycisk, 2004 Wycisk et al., 2002) or polyacrylonitrile (Carter et al., 2002) or a reactive polymer (e.g., polybenzimidazole) (Wycisk et al., 2005) have been investigated. The resultant membranes had conductivities of 0.01-0.06 S/cm (in water at 25°C) and equilibrium water swelling from 20 to 60% (at 25°C). Blends of poly[(bisphe-noxy)phosphazene] and polybenzimidazole (where acid-base complexation occurred between the sulfonic acid and the imidazole nitrogen) exhibited good mechanical properties and low methanol permeability. MEAs with this membrane material outperformed Nafion 117 in a DMFC at 60°C with concentrated (5-10 M) methanol feeds. With 1.0 M methanol and 0.5 L/min ambient air at 60°C, the maximum power density was 97 mW/cm and the methanol crossover was 2.5 times lower than that with Nafion 117 (Wycisk et al., 2005). 

Further work on sulfonated poly[fc X3-methylphenoxy)phosphazene] (SPBMPP) confirmed that methyl groups promoted aromatic ring sulfonation, which started when the ratio of SO3 to the polymer was higher than 0.64 [81], For the sulfonated polymers with an lEC lower than 1.0 mmol g , the sulfonation mainly occurred at the para position, while all available carbon atoms at the aromatic ring could be attacked by SO3 when the polymer lEC was higher than 1.0 mmol g". It was also found that during the sulfonation process, there was always the formation of... 

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