Ionomer membrane systems

Use of sulfonated polymers as the proton-conductive component in the fuel cell membranes at T < 100°C Use of nonfluorinated ionomers physical and/or chemical cross-linking of the fuel cell membranes Use of nonfluorinated ionomers physical and/or chemical cross-linking of the fuel cell membranes Development of organic-inorganic composite membranes, based on our cross-linked ionomer membrane systems, in which the inorganic membrane component serves as water storage or even contributes to H -conduction Use of commercially available polymers for chemical modification and membrane formation, which avoids expensive development of novel polymers... 

Comparison of the Properties of the Different Ionomer Membrane Systems... 

Paddison, S. J. 2001. The modeling of molecular structure and ion transport in sulfonic acid based ionomer membranes. Journal of New Materials for Electrochemical Systems 4 197-207. 

So far, CG approaches offer the most viable route to the molecular modeling of self-organization phenomena in hydrated ionomer membranes. Admittedly, the coarse-grained treatment implies simplifications in structural representation and in interactions, which can be systematically improved with advanced force-matching procedures however, it allows simulating systems with sufficient size and sufficient statishcal sampling. Structural correlations, thermodynamic properties, and transport parameters can be studied. 

Industrial applications of perfluorinated ionomer membranes such as the electrolysis of sodium chloride solution to produce chlorine and sodium hydroxide often involve the use of highly concentrated solutions at elevated temperatures. The optimization of these systems depends upon a sound characterization of membrane transport processes under such conditions. Sodium ion is the major current-carrying species through the membrane in a chlor-alkali cell, and... 

Neutralizing the acid groups in the dispersion leads to formation of an ionomer membrane in the latex film [63]. As shown in Figure 14.24, this ionomer phase has a profound effect on slowing down the interdifiusion and on broadening the distribution of diffusion rates. In spite of the complexity of the system, there is a quite simple explanation for these effects. The shell polymer has a higher Tg than that of the core. The Tg of the shell phase depends upon composition the... 

The main question addressed in this review was what role do the competing interactions play for the struetural properties of hydrated ionomer membranes at low water contents. The behavior of such systems, in particular, their nanoscale organization, is dictated by the relative strength of the competing hydrophobic/polar interactions and can be tuned by varying parameters such as temperature, hydration level, and molecular architecture. 

It should bear in mind that the requirements for active DAFC could be significantly different than the passive DAFC systems used for lower power, portable applications [4]. Water balance and alcohol crossover become more critical in passive cell systems, where information on the performance of advanced ionomer membranes is limited by the cmifidential nature of the research and development. 

Substitution of currently used perfluorosidfonic acid (PFSA) ionomers and ionomer membranes (e.g., Nafion ) by novel materials with substantially improved proton conductivity at low relative humidity (RH), which would ehminate the need for fuUy humidified reactants and thereby significantly simplify fuel cell system design [2, 4, 5]. 

The focus in the thin film research impact area is to develop a fundamental understanding of how morphology can be controlled in (1) organic thin film composites prepared by Langmuir Blodgett (LB) monolayer and multilayer techniques and (2) the molecular design of membrane systems using ionomers and selected supported liquids. Controlled structures of this nature will find immediate apphcation in several aspects of smart materials development, particularly in microsensors. 

A tryiuoromethane sulfonic acid monohydrate (TAM) solid was explored by Eikerling et al. (2003). Although this system does not resemble a structure for surface proton conduction in the PEM, it allows studying correlation effects at high density of triflic acid groups, the sidechain head groups in PFSA ionomer membranes, and under conditions of low hydration. 

Elhott, J. A., EUiott, A. M. S., and Cooley, G. E. 1999. Atomistic simulation and molecular dynamics of model systems for perfluorinated ionomer membranes. 

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