Electrical properties of sulfonated polyether ether ketone/polyetherimide blend membranes doped with inorganic acids

The influence of blending with polyetherimide (PEI) and doping with HCl and H3PO4 on the properties of sulfonated polyether ether ketone (SPEEK) was s tudied. Blending with PEI first results in an increase and then in a decrea se in membrane swelling at PEI concentrations greater than 5%. The electric al conductivity of blend membranes follows the same trend. Doping with the acids enhances the conductivity several times, and the effect of doping wit h HCl is more significant. PEI forms spherical particles dispersed in the S PEEK matrix and, at the same time, partially dissolves in SPEEK, which redu ces the swelling of the matrix at higher PEI concentrations. The increase i n the membrane capacity to absorb water at small PEI contents is due to the formation of new water adsorption sites along the interface between the pa rticles and the matrix. A modified effective medium model yielded calculate d results in good agreement with the measured conductivity values, when the experimental absorption data were used in the simulation. (C) 2000 John Wi ley & Sons, Inc.