Evidence for a novel type of gas-phase cationic polymerization process is described. Gas-phase ions consisting of a perfluorinated ion attached to an assembly of cyclic ether or thioether molecules, such as ethylene oxide, ethylene sulfide, and tetrahydrofuran, are formed in the chemical ionization source of a mass spectrometer. The ions contain up to five ether molecules depending on the size of the perfluorinated compound and the nature of the ether involved in the reaction. The highly strained ethylene oxide forms product ions containing the most ether molecules bound to a perfluorinated substrate, whereas the unstrained acyclic dimethyl ether results in product ions containing only a single ether molecule. The experimental results suggest that the cyclic ethers attach to a perfluorinated substrate ion and then undergo ring-opening gas-phase polymerization in the gas phase to form an extended polyether chain which is covalently bound to the perfluorinated substrate. Collisionally activated dissociation techniques were used to further characterize the structures of the ions.