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Percolation transition and conductivity in macroscopically anisotropic two‐component polymer membranes
Author(s) -
Narȩbska Anna,
Wódzski Romuald,
Bukowski Zbigniew
Publication year - 1986
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.1986.070310601
Subject(s) - volume fraction , materials science , percolation (cognitive psychology) , critical exponent , membrane , anisotropy , polymer chemistry , exponent , conductivity , percolation theory , phase transition , condensed matter physics , thermodynamics , composite material , chemistry , physics , optics , neuroscience , biology , biochemistry , linguistics , philosophy
Percolation conductance has been studied for polypropylene/poly(acrylic acid) membranes (PP‐ g ‐PAA) prepared by volume grafting of an ionic component onto polypropylene foil. In these membranes the volume fraction of the conducting phase decreases from the surface to the center, brining some anisotropy into the composition. For this material, the “insulator‐ to‐conductor” transition proceeds at a critical volume fraction V c equal to 0.395. It has been proved that this critical volume fraction and the critical exponent t , found to be below that predicted by theory, i.e., 1.2 ± 0.03 instead of 1.6 ± 0.2, result from the gradient in the distribution of the conducting component in the direction of the current flow. Computations of V c and t for the same PP‐ g ‐PAA copolymer with a randomly distributed conducting component have led to V c = 0.08 and t * = 1.53. A critical exponent t in that range is characteristic of three‐dimensional systems; however, V c is rather low, suggesting a nonspherical shape for the conducting domains.