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Percolation conductivity in Nafion membranes
Author(s) -
Wódzki Romuald,
Narębska Anna,
Nioch Wojciech Kwaś
Publication year - 1985
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1985.070300225
Subject(s) - nafion , membrane , ionomer , percolation (cognitive psychology) , volume fraction , conductivity , electrolyte , percolation threshold , materials science , sodium hydroxide , ionic conductivity , chemical engineering , chemistry , polymer chemistry , analytical chemistry (journal) , inorganic chemistry , chromatography , electrical resistivity and conductivity , composite material , polymer , physics , copolymer , electrode , biochemistry , quantum mechanics , neuroscience , engineering , electrochemistry , biology
Abstract This article deals with the method of determination of a threshold volume fraction of the conductive phase within perfluorosulfonic acid ionomer Nafion. Experiments have been performed with the commercial Nafion‐120 and Nafion‐427 membranes equilibrated with concentrated sodium chloride and sodium hydroxide solutions at 353 K. It has been stated that the insulator‐to‐conductor transition in membranes occurs at the critical volume fraction of the conductive phase ( V c ) equal to 0.1. The same V c has been estimated for a geometrical cluster‐network model. Lower than the theoretical V c for a classical dense‐packed‐hard‐sphere model ( V c = 0.15), the volume fraction for the membranes is caused mainly by channels connecting the ionic clusters. The critical exponent t has been calculated for both membranes and found to be equal to 1.6 for Nafion‐120 and 1.5 for Nafion‐427. Both these constants correspond to those theoretically predicted for 3D systems. The ratios of sodium ion mobility in the internal membrane solution to its mobility in the equilibrating NaCl or NaOH solutions ( u + / u + ) are below unity, and they are dependent on the nature and concentration of the electrolyte.