Sulfonated fluorochlorocarbon ionomer films were prepared by radio frequency plasma polymerization of trifluorochloroethylene (TFCE) and trifluoromethane sulfonic acid (TFMSA). The TFMSA was introduced into the plasma chamber by bubbling a carrier gas through a vessel containing the neat acid. We show that the sulfonate content of the film prepared can be controlled by varying the temperature of the TFMSA-containing vessel. We also show that films with high sulfonate contents can be prepared by using TFCE as the carrier gas for the TFMSA and then allowing this gas mixture to sustain the plasma. This may be contrasted to previous experiments of this type, where Ar was used to sustain the plasma and as the carrier gas. To our knowledge, this approach (i.e., of using the reactant gases to support the plasma) has never been used in the synthesis of plasma-polymerized films. Finally, we have measured the ionic conductivities of the plasma-polymerized films. The films prepared from the TFCE plasma are an order of magnitude more conductive than the films prepared from the Ar plasma.