Fuel cells have the potential to become an important energy conversion technology. Research efforts directed toward the widespread commercialization of fuel cells have accelerated in light of ongoing efforts to develop a hydrogen-based energy economy to reduce dependence on foreign oil and decrease pollution. Proton exchange membrane (also termed “polymer electrolyte membrane”) (PEM) fuel cells employing a solid polymer electrolyte to separate the fuel from the oxidant were first deployed in the Gemini space program in the early 1960s using cells that were extremely expensive and had short lifetimes due to the oxidative degradation of their sulfonated polystyrene-divinylbenzene copolymer membranes. These cells were considered too costly and short-lived for real-world applications. The commercialization of Nafion by DuPont in the late 1960s helped to demonstrate the potential interest in terrestrial applications for fuel cells, although its major focus was in chloroalkali processes. PEM fuel cells are being developed for three main applications: automotive, stationary, and portable power. Each of these applications has its unique operating conditions and material requirements. Common themes critical to all high performance proton exchange membranes include (1) high protonic conductivity, (2) low electronic conductivity, (3) low permeability to fuel and oxidant, (4) low water transport through diffusion and electro-osmosis, (5) oxidative and hydrolytic stability, (6) good mechanical properties in both the dry and hydrated states, (7) cost, and (8) capability for fabrication into membrane electrode assemblies (MEAs). Nearly all existing membrane materials for PEM fuel cells rely on absorbed water and its interaction with acid groups to produce protonic conductivity. Due to the large fraction of absorbed water in the membrane, both mechanical properties and water transport become key issues. Devising systems that can conduct protons with little or no water is perhaps the greatest challenge for new membrane materials. Specifically, for automotive applications the U.S. Department of Energy has currently established a guideline of 120 °C and 50% relative humidity as target operating conditions, and a goal of 0.1 S/cm for the protonic conductivity of the membrane. New membranes that have significantly reduced methanol permeability and water transport (through diffusion and electro-osmotic drag) are required for portable power oriented direct methanol fuel cells (DMFCs), where a liquid methanol fuel highly diluted in water is used at generally <90 °C as the source of protons. Unreacted methanol at the anode can diffuse through the membrane and react at the cathode, lowering the voltage efficiency of the cell and reducing the system’s fuel efficiency. The methanol is usually delivered to the anode as a dilute, for example, 1 M (or less), solution (3.2 wt %), and relatively thick Nafion 117 (1100 EW, 7 mil ∼ 178 μm thick) is used to reduce methanol crossover. The dilute methanol feed increases the system’s complexity and reduces the energy density of the fuel, while the thick Nafion membrane increases the resistive losses of the cell, especially when compared to the thinner membranes that are used in hydrogen/air systems. The presence of excessive amounts of water at the cathode through diffusion and electro-osmosis * To whom correspondence should be addressed. E-mail: jmcgrath@vt.edu. † Sandia National Laboratory. ‡ Case Western Reserve University. § Los Alamos National Laboratory. | Virginia Polytechnic Institute and State University. 4587 Chem. Rev. 2004, 104, 4587−4612

Alternative Polymer Systems for Proton Exchange Membranes (PEMs)

http://www.engr.uconn.edu/~jmfent/membrane%20review%201.pdf

Proton-conducting polymer electrolyte membranes based on hydrocarbon polymers

Methods in Lignin Chemistry

Synthesis and characterization of sulfonated poly(ether ether ketone) for proton exchange membranes

https://faculty.kfupm.edu.sa/che/zaidismj/publications/membranes_heteropolyacids_fuelcells_memb.pdf

Proton conducting composite membranes from polyether ether ketone and heteropolyacids for fuel cell applications

Proprietes des solutions diluees de poly(oxy phenyleneoxy phenylenecarbonyl phenylene-1,4) dans l'acide sulfurique et HSO 3 Cl. Modification chimique du polymere dans ces acides

Solubility and properties of a poly(aryl ether ketone) in strong acids

Experimental Evidence for a Departure from the Law of the Rectilinear Diameter

Detection of a major conformational change in transfer ribonucleic acid by laser light scattering

The capacity to respond to chemical and physical stimuli
is an essential characteristic of biological membranes.
Intercellular communication and recognition, response to
the binding of drugs and hormones, photoreception, and
many other critical cellular functions are in fact membrane
processes in biology and are subject to control as a result
of the responsive nature of the bilayer membrane.

pH-dependent vesicle-to-micelle transition in an aqueous mixture of dipalmitoylphosphatidylcholine and a hydrophobic polyelectrolyte

Relation entre la masse moleculaire et le coefficient de diffusion translationnelle, dans trois verres differents, de solutions diluees de polystyrene dans un bon solvant

Kenneth H. Langley

Papers

Solubility and properties of a poly(aryl ether ketone) in strong acids

Experimental Evidence for a Departure from the Law of the Rectilinear Diameter

Detection of a major conformational change in transfer ribonucleic acid by laser light scattering

pH-dependent vesicle-to-micelle transition in an aqueous mixture of dipalmitoylphosphatidylcholine and a hydrophobic polyelectrolyte

Dynamic light-scattering studies of polymer diffusion in porous materials: linear polystyrene in porous glass