Ultrathin, cross-linked polyimide pervaporation membranes prepared from polyelectrolyte multilayers

摘要: Abstract Alternating electrostatic adsorption of poly(amic acid) salts and polycations on porous alumina supports followed by heat-induced imidization yields ultrathin, polyimide membranes. Moreover, incorporation additional carboxylic acid groups in the allows cross-linking via reaction these with amines polycation. FTIR spectroscopy confirms both full formation amide cross-links after heating at 250 °C for 2 h, while scanning electron microscopy reveals uniform, ∼50 nm thick films based 7.5–12.5 acid)/polycation bilayers. Pervaporation was investigated as a function varying either polycation, i.e., poly(allylamine hydrochloride), polyethylenimine, or poly(diallyldimethylammonium chloride), number cross-linkable acid). Maximum cross-linkage selectivities occur imidized prepared from hydrochloride) that contains diaminobenzoic each repeat unit. Such membranes exhibit water/alcohol 1100 6100 solutions containing 10 90% isopropanol, respectively, minimal thickness multilayer still to fluxes 11 2 kg m−2 h−1, respectively. Fluxes are essentially same water/ethanol solutions, but decrease 100 500 ethanol,