Multilayered films based on macrocyclic polyamines, calixarenes and cyclodextrins and transport properties of the corresponding membranes

A survey is given on our recent studies on layer-by-layer (lbl) assembled hybrid films and membranes of charged macrocyclic compounds and oppositely charged polyelectrolytes. As macrocycles, p-sulfonato-calix[n]arenes with n = 4, 6, and 8, 1,4,7,10,13,16-hexaazacyclooctadecane (hexacyclen, 18-azacrown-6), and per-6-amino-β-cyclodextrin were used. Films and membranes were prepared upon alternating electrostatic adsorption of the charged compounds at solid substrates. Film formation was characterized upon spectroscopic methods. Effects of pH and ring size were investigated. Separation properties of membranes deposited on porous substrates were studied. Calixarene-based membranes exhibit a highly selective transport of metal ions, while hexacyclen-based membranes show a highly selective anion transport. Theoretical separation factors α(NaCl/YCl3) of 160 and α(NaCl/Na2SO3) of 1420 were obtained. Cyclodextrin-based membranes exhibit a size-selective transport of aromatic compounds. Possible origins for the high transport selectivities are discussed.