Electrical conductivity of polyaniline/zeolite composites and synergetic interaction with CO

The effects of zeolite content, pore size and ion exchange capacity on electrical conductivity response to carbon monoxide (CO) of polyaniline/zeolite composites were investigated. Zeolite Y, 13X, and synthesized A1MCM41, all having the common cation Cu2+, were dry mixed with synthesized maleic acid (MA) doped polyaniline and compressed to form polyaniline (PANI)/zeolite pellet composites. The Y, 13X and A1MCM41 zeolite have the nominal pore sizes of 7, 10, 36 angstrom, and the Cu2+ exchange capacities of 0.161, 0.087, and 0.044 mol/g, respectively. With an addition of 13X zeolite to pristine polyaniline, the electrical conductivity sensitivity to CO/N-2, gas increases with zeolite content. For the effect of zeolite type, the highest electrical conductivity sensitivity is obtained with the 13X zeolite, followed by the Y zeolite, and the A1MCM41 zeolite, respectively. Poor sensitivity of zeolite A1MCM41 is probably due to its very large pore size and its lowest CU2+ exchange capacity. Y zeolite and 13X zeolite have comparable pore sizes but the latter has a greater pore free volume and a more favorable location distribution of the Cu2+ ions within the pore. The temporal response time increases with the amount of zeolite in the composites but it is inversely related to the amount of ion exchange capacity. (c) 2004 Published by Elsevier B.V.