Monday, November 23, 2009

Copolymers with Nanoscale Ionic Channels Improve Fuel Cell Membranes & Protective Fabrics


University of Tennessee Research Foundation (Knoxville, TN) researchers have developed copolymers of fluorinated polydienes and sulfonated polystyrene for use in proton exchange fuel cell membranes, batteries, solar cells,  breathable chemical-biological protective materials, agricultural product protection and templates for sol-gel polymerization. Poly(styrene sulfonic acid) (PSS) is an effective proton conductor.  Applications of the fluorinated and sulfonated materials for use as barrier materials for chemical-biological protection or as fuel cell membranes require good mechanical strength and toughness, and in the case of fuel cells good mechanical properties at elevated temperatures  between about 100.degree C and 150 degree C.

According to the inventors Jimmy W. Mays, Samuel P. Gido, Tianzi Huang and Kunlun Hong, if the composition of the copolymer is chosen so that the fluorinated polybutadiene (FPB) volume fraction is considerably larger than the PSS volume fraction, i.e., the content of sulfonated polystyrene in the copolymer is relatively low, then a structure having a hydrophobic semi-crystalline continuous phase containing dispersed nanoscale ionic channels is obtained via self-assembly. By tuning the composition, molecular weight, and architecture (readily done using anionic polymerization), the morphology, structure, and properties is manipulated and can be used for a variety of applications as detailed in U.S. Patent 7,619,036.

The disclosed copolymers of fluorinated polydienes and sulfonated polystyrene and, in some embodiments, cross-linked poly(1,3-cyclohexadiene (PCHD) polymers can  also be used as a barrier fabric. The fabrics can find applications as breathable chemical-biological protective barrier clothing to protect military personnel, emergency response teams, industrial and/or agricultural workers, and healthcare professionals from chemical and/or biological agents, including hazardous and/or toxic chemicals and microorganisms, such as, but not limited to, chemical-biological warfare agents, viruses, bacteria, blood-borne pathogens, air-borne pathogens, industrial chemicals, and agricultural chemicals, in liquid, vapor, and aerosol forms. Further, such materials allow perspiration products to escape from a body, while preventing the penetration and/or transport of  hazardous and/or toxic materials.

Further, the barrier fabric can be used to protect agricultural products, including living and cultivated vegetative products from exposure to natural pathogens, such as fungi, chemical and/or biological pathogens, and frost. It can also be used as a barrier fabric for use as a "weed barrier," which impedes the growth of undesired vegetative species, while retaining moisture in the soil.

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