The permeability to H-2, O2, and N2 of silicon-containing polypyrrolone (SiDA-OTA) and three silicon-containing polypyrrolone random copolymers was determined at 30-degrees-C and 1 atm. The SiDA-OTA shows simultaneously increased permeability and permselectivity over the analogous polyimide (SiDA-ODA). The substitution of SiDA for the BPDA moiety in a polypyrrolone appears to result in a significant increase in gas permeability. The random copolymers contain different amounts of SiDA and DODA, which show lower permeability and higher permselectivity than does SiDA-OTA. Wide-angle X-ray diffraction measurements of the mean intersegmental distance of the materials characterized the packing of different polymer types.