Control of chemical, thermal, and gas transport properties in dense phosphazene polymer membranes

Polyphosphazenes are hybrid polymers having organic pendant groups attached to an inorganic backbone. Phosphazene polymers can be tailored to specific applications through the attachment of a variety of different pendant groups to the phosphazene backbone. Applications for which these polymers have proven useful include solid polymer electrolytes for batteries and fuel cells, as well as, membranes for gas and liquid separations. In past work, phosphazene polymers have been synthesized using mixtures of pendant groups with differing chemical affinities. Specific ratios of differing pendant groups were placed on the phosphazene backbone with a goal of demonstrating control of solubility, and therefore chemical selectivity. In this work, a series of phosphazene homo-polymers were synthesized having varying amounts of hydrocarbon and polyether character on each individual pendant group. The polymers were synthesized with the polyether portion next to the polymer backbone and the hydrocarbon portion on the terminal end of the pendant group. The effects of these combined hydrocarbon/polyether pendant groups on polymer morphology and gas transport properties are presented. The following data is presented: thermal characterization, pure gas permeability of six gases (Ar, H ₂, O ₂, N ₂, CO ₂, and CH ₄), and ideal selectivity for the gas pairs: O ₂/N ₂, H ₂/CO ₂, CO ₂/H ₂, CO ₂/CH ₄ and CO ₂/N ₂.