SPTES polymer membranes

The acid form of the SPTES membranes has a much higher water uptake than the corresponding salt form of the SPTES membranes. The water uptake increased nonlinearly from 41% for SPTES-50 membrane to 300% for SPTES-lOO membrane of acid form, while the salt form of SPTES polymer membranes also shows increased water uptake (4.93-72.8%) with increased degree of sulfonation. The SPTES polymer membranes show much higher water uptake compared with Nafion... 

In Fig. 6.10, the water uptake of Nafion is much lower compared with the SPTES polymers, especially those with high sulfonic acid content. While the water uptake of the SPTES polymer membranes increases steeply at higher temperatures, the water uptake of Nafion is shown to be relatively insensitive to temperature changes. 

The proton conductivities of the SPTES polymer membranes in the longitudinal direction were measured by AC impedance spectroscopy. All SPTES polymer membranes were initially hydrated by immersion in deionized water for at least 24 h at... 

Figure 6.12 shows the results of the proton conductivity of the SPTES polymers and Nafion-117 at 85% relative humidity at different temperatures. In all the cases, an increase of the membrane proton conductivity with increasing temperature is indicated. All the SPTES polymer membranes exhibited higher proton conductivity than Nafion-117 except in the lower temperature region for SPTES-50 polymer where a slight crossover is indicated. The proton conductivities of SPTES polymers have a linear dependence on temperature, thus showing Arrhenius behavior. The activation energy related to the proton conductivities of the SPTES polymers has been reported elsewhere [29]. 

The synthesized SPTES polymers with the endcapping group could be readily cast into membranes of both salt form and acid form. The physical properties of the SPTES polymers are listed in Table 6.2,... 

In all these conditions, SPTES-50 polymer membranes exhibited greater strength than Nafion-117. It is worth mentioning that the tensile strength of wet... 

A series of dynamic X-ray scattering experiments were also performed (Fig. 6.22). A swollen SPTES-70 membrane was examined by X-ray diffraction. X-ray scans were taken at a series of time intervals of 10 min in a drying experiment. The intensity and peak position was monitored at 10 min time intervals for nearly 2 h until the sample was dried (Fig. 6.22). The intensity and the position of the polymer... 

A higher current density of 0.52 amp cm was obtained for the SPTES-50 polymer membrane-based MEA as compared with a current density of 0.24 amps cm for Nafion-117 membrane-based MEA at 0.6 V potential. Similarly, a higher peak power density of 0.34 W cm was obtained using SPTES-50 polymer membrane compared with 0.16 W cm using Nation-117 membrane in MEAs, measured under the same conditions. Estimates of hydrogen fuel permeability based upon measured open circuit voltage (OCV) indicate that SPTES-50 MEA and Nafion-117 exhibit similar rates of fuel crossover. 

Chapters 6 and 7 deal with the hydrocarbon polymers and composites targeted for high temperature PEM fuel cell applications. Specifically, chapter 6 deals with a series of high molecular weight, highly sulfonated poly(arylenethioethersulfone) (SPTES) polymers synthesized by polycondensation. They were characterized by different methods and tested for proton conductivity. Finally, membrane electrode assemblies (MFAs) were fabricated. 

Wang XL, Oh IK, Chen TH (2010a) Electro-active polymer aetuators employing sulfonated poly (styrene-ran-ethylene) as ionic membranes. Polym Int 59(3) 305 312 Wang XL, Oh IK, Lee S (2010b) Electroactive artificial muscle based on crosslinked PVA/SPTES. Sensor Actuators B 150(l) 57-64... 

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