Propane and propylene sorption in solid polymer electrolytes based on poly(ethylene oxide) and silver salts

The sorption of propylene and propane in solid polymer electrolytes based on blends of poly(ethylene oxide) (PEO) and silver nitrate, AgNO₃, silver triflate, AgCF₃SO₃, silver trifluoroacetate, AgCF₃CO₂, or silver tetrafluoroborate, AgBF₄, are reported. These solid polymer electrolytes exhibit preferential sorption for propylene over propane due to complexation of propylene with silver ions in the polymer matrix and reduced propane solubility in the solid polymer electrolyte films relative to that in PEO alone. The order of olefin solubility in blends containing 1mol of silver ions per mole of ethylene oxide (EO) units is: AgBF₄>AgCF₃SO₃> AgCF₃CO₂>AgNO₃. At 35°C and 40cmHg pressure, a PEO/AgBF₄ film containing 1mol of silver ions per mole of EO sorbed 5.3g propylene but only 0.083g propane per 100g of solid polymer electrolyte. AgBF₄ is highly soluble in PEO and completely disrupts polymer crystallinity even at low salt concentration (approximately 10wt.%) without significantly altering the glass transition temperature. Other silver salts (e.g. AgNO₃) do not dissolve completely in PEO and are much less effective at promoting enhanced olefin solubility.