Polyazole Membranes
Polyazole block polymers because of their outstanding chemical and thermal properties are suitable in particular as polymer electrolyte membrane (PEM) in so-called PEM fuel cells.
Polyazoles, for example polybenzimidazoles have been known for sometime. Such polybenzimidazoles (PBIs) are prepared typically by reacting 3,3',4,4'-tetraaminobiphenyl with isophthalic acid or diphenylisophthalic acid or their esters thereof in the melt. The prepolymer formed solidifies in the reactor and is subsequently comminuted mechanically. Subsequently, the pulverulent prepolymer is finally polymerized in a solid-phase polymerization at temperatures of up to 400.degree. C. and the desired polybenzimidazoles are obtained.
To prepare polymer films, the PBI, in a further step, is dissolved in polar, aprotic solvents, for example by dimethylacetamide (DMAc) and a film is obtained by means of classical processes. The basic polyazole films are doped with concentrated phosphoric acid or sulfuric acid and then act as proton conductors and separators in so-called polymer electrolyte membrane fuel cells (PEM fuel cells).
As a result of the outstanding properties of the polyazole polymers, such polymer electrolyte membranes, processed to give membrane-electrode units (MEE), can be used in fuel cells at long-term operating temperatures above 100.degree. C., in particular above 120.degree. C. This high long-term operating temperature allows it to increase the activity of the noble metal-based catalysts present in the membrane-electrode unit (MEE).
(Calundann et al, US Patent 7,820,314; 10/26/2010)
Applications
Electrical Applications
Fuel Cells
Proton Exchange Membranes
Recent US Patents
10/26/2010
7,820,314
Proton-conducting membrane and use thereof
Calundann et al of BASF, Germanyhave developed a proton-conducting polymer membrane based on polyazole block polymers as polymer electrolyte membrane (PEM) for fuel cells. A proton-conducting membrane based on polyazole block polymers can be obtained when the parent monomers are suspended or dissolved in polyphosphoric acid and first polymerized up to a certain degree, and these are then mixed and polymerized to block polymers. (RDC 2/17/2011)