Gas separation investigations on polyaniline composite membranes

Composite homogeneous polyaniline (PANI)/(5%) polystyrene (PS) membranes cast from benzene solutions and composite laminar membranes were studied to determine the permeability coefficients of hydrogen, nitrogen and air, and hence to evaluate the selectivity coefficients in the O₂/N₂ and H₂/N₂ systems (Tables 1, 2). The thickness of PANI layer did not affect the permeability coefficients. With PS as carrier substrate, the resulting membranes could not be made less than 5 μm thick in active layer; they had permeation properties close to those of pure PANI membranes and were mechanically stable over a pressure range of 0.3-0.5 MPa; such membranes correspond to pure PANI membranes 25 μm thick; pure PANI membranes 5 μn thick were entirely unsuitable for permeation studies at the pressures applied. In the homogeneous membranes prepared by emulsion polymerization, PANI 40-65 μm/PS 35 μm, the permeability coefficients decreased as the PANI content was increased. The gas molecules permeated along pathways offering the least resistance to flow, i.e., as in a composite with PANI content equal to zero; the permeation coefficients of such membranes are close to those of polystyrene membranes. Likewise permeability, the selectivity coefficients were only slightly affected by active layer thickness.