A strategy to molecularly optimize the cathode side of a proton exchange membrane fuel cell is described. This new cathode consists of a porous alumina membrane with metal-lined pores that function as gas diffusion conduits while supporting a catalyst layer and ionomer. The ionomer chains are grown from the surface of the pore walls and are designed to encapsulate the catalyst particles to provide a well-defined three-phase boundary for gas, proton, and electron transfer. Two new classes of ionomer were evaluated, including non-fluorinated and partially fluorinated polymers prepared by the surface-initiated ring-opening metathesis polymerization of a functionalized norbornene and subsequent sulfonation with acetyl sulfate. These ionomers were grown rapidly and conformally over any surface geometry with nanometer-level control over thickness. The effectiveness of a high-utilization catalyst attachment method was demonstrated through electrochemical monitoring of the oxygen reduction reaction. This is an abstract of a paper presented at the 2007 AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).