Polyphosphazenes are hybrid polymers having organic pendant groups attached to an inorganic backbone. The inorganic backbone provides these materials with good chemical and mechanical stability. In addition, phosphazene materials can be tailored to specific applications through the placement of organic pendant groups on the phosphazene backbone. Tailoring phosphazene polymers can yield materials with widely varying physical characteristics, such as, glass transitions that range from -80 „aC to 50 „aC. Polymer morphology that ranges from amorphous rubbery to glassy can be created with the careful selection of pendant groups.

In this study two different homo-polymers were synthesized using the following organic pendant groups; 2-phenoxyethanol and 4-tert-butyl-2-phenoxyethanol. The effects of these pendant groups on polymer morphology and on the gas transport properties are presented. Pure gas permeability measurements were made using the time-lag method. Permeabilities for six gases (He, H2, O2, N2, CO2, and CH4) were determined over a range of temperatures from -20 „aC to 75 „aC, thus providing gas transport information both above and below the polymer glass transition. Activation energies will be presented. Ideal selectivity for the gas pairs: O2/N2, H2/O2, H2/CO2, and CO2/CH4 are addressed.