Abstract
Hybrid silica gel-polyphosphazene membranes were prepared by acid hydrolysis of tetraethoxysilane and co-condensation with catenapoly[bis(4- hydroxyphenoxy)phosphazene] and contacting the resulting solution with tubular ceramic supports (4-10 nm pore size). The morphology of the membranes (SEM) was first optimized, then other membranes were prepared and characterised by Field Emission SEM and gas permeability (N2, He and CO2). The He/N2 selectivity values indicated a predominant Knudsen diffusion transport mechanism, and were not as high without the polyphosphazene (pure silica gel). The He/CO2 selectivity was markedly below the Knudsen diffusion limit, suggesting a possible additional contribution of surface diffusion to the overall transport of CO2.
