Accession Number : ADA294692

Title :   Charge Transport and Water Molecular Motion in Variable Molecular Weight NAFION Membranes. High Pressure Electrical Conductivity and NMR.

Descriptive Note : Interim Technical rept.,

Corporate Author : HUNTER COLL NEW YORK

Personal Author(s) : Fontanella, J. J. ; Wintersgill, M. C. ; Chen, R. S. ; Wu, Y. ; Greenbaum, S. G.

PDF Url : ADA294692

Report Date : 26 MAY 1995

Pagination or Media Count : 29

Abstract : Measurements of the electrical conductivity and deuteron NMR spin-lattice relaxation time (T1) in the three different molecular weights of acid form NAFION conditioned at various levels of relative humidity have been carried out. Complex impedance studies were made along the plane of the film at frequencies from 10 to 10(exp 8) Hz at room temperature and pressure up to 0.3 GPa. The NMR measurements were also made at room temperature and pressures up to 0.25 GPa. For all materials, the electrical conductivity decreases with increasing pressure. The calculated activation volume exhibits a large decrease (from 16 to 3 cu cm/mol) as the water content is increased from 2.4 Wt-% to 8 Wt-%. The activation volumes extracted from the NMR data show only a small further decrease as the water content is increased from 6 to 22 Wt-%. The activation volume dependence on water content represents further evidence that the transport mechanism in low water content materials is dominated by large scale segmental motions of the polymer chain, whereas at higher water content the conductivity is more strongly influenced by the water than by the polymer. Finally, the data show that the electrical conductivity is smaller and the activation volume is larger for the higher molecular weight material. jg

Descriptors :   *WATER, *MOLECULAR WEIGHT, *ELECTRICAL CONDUCTIVITY, *CHARGE TRANSFER, *MEMBRANES, ACTIVATION, NUCLEAR MAGNETIC RESONANCE, MOLECULES, MATERIALS, POLYMERS, COMPOSITE MATERIALS, FILMS, MOTION, HIGH PRESSURE, MOISTURE CONTENT, ROOM TEMPERATURE, VARIABLES, CHAINS, TRANSPORT, LATTICE DYNAMICS, IMPEDANCE, HUMIDITY, ION EXCHANGE, SPIN STATES, ACIDS, DEUTERONS.

Subject Categories : Physical Chemistry
      Inorganic Chemistry
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE