Polymer Electrolytes Based on Ionomeric Copolymers of Ethylene with Fluorosulfonate Functionalized Monomers

The copolymerization of ethylene with α-olefinic fluorosulfonyl fluoride monomers using organometallic catalysts provides a new class of ionomeric polymer electrolytes. These hydrocarbon-based ionomeric polymers utilize strong acid-functional groups based on the fluorosulfonate anion the same anionic group used in the Nafion perfluorinated ionomer membrane. The Versipol™ catalyst system generates short-chain branches on the copolymers giving amorphous to semicrystalline copolymers that exhibit good organic solvent swelling and high lithium-ion conductivities. Metallocene catalysts are also able to make these copolymers, but with much higher crystallinity. By introducing a third monomer such as 1-octene to break down the crystallinity of metallocene-catalyst-based ethylene copolymers, the resulting terpolymers also conduct lithium ions well when swollen with organic solvents. Propylene-based copolymers with fluorosulfonyl fluoride monomers were also made and tested for conductivity, but the results were less satisfactory.