Novel highly permselective 6F-poly(amide-imide)s as membrane host for nano-sized catalysts

Poly(amide-imide)s (PAIs) combine properties of amide and imide polymers. On a synthetic route starting with preformed imide monomers (as dicarboxylic acids) and diamines, PAIs are readily available in various structures and different properties. Hexafluoroisopropylidene (6F) units are element of the dicarboxylic acid or diamine part or both parts of the PAI. Tailoring of the polymer was achieved to high permselectivities and ability to generate nano-sized noble metal catalysts in high amounts, > 20 wt% noble metal, inside the polymer membranes. Even at high catalyst loading, the films remained flexible. Gas permeabilities up to 15 barrer for O₂ ( p_O2 p_N2 = 5.4) and 100 barrer for H₂ ( p_H2 p_N2 = 35) and selectivities up to 7.6 for p_O2 p_N2 (p_O2 = 1.8 barrer) and 100 for p_H2 p_N2 (p_H2 = 23 barrer) were measured. Gas permeability and selectivity data of CH₄, N₂, O₂, He, H₂ and CO₂ are reported. In addition, various salts in amounts up to 50 wt% were incorporated into the films and chemically transformed to catalysts. These catalysts generated inside the membrane were homogeneously distributed, still active and homogeneous in size (∼ 2 nm). The influence of salts and catalysts on the gas permeation properties of these nonporous membranes is discussed and their catalytic activity is shown by hydrogen sorption. Thin film composite membranes on PVDF supports with and without catalyst were prepared and their permselectivity data are reported.