Fuel cell technology represents a promising approach towards alternative and renewable clean energy. Fuel cells operate by converting chemical energy into electrical energy via a chemical reaction between reductants (e.g., hydrogen or hydrocarbons) and oxidants such (e.g., oxygen). Proton-exchange membrane fuel cells (PEMFCs) are devices, which deliver power by shuttling protons catalytically generated from hydrogen fuel from the anode to the cathode, producing water as the only byproduct. The efficiencies and durabilities of PMFCs are determined, primarily, by the properties of the proton exchange membranes (PEMs). PEMFCs show higher efficiencies than traditional engines. While internal combustion engines can routinely achieve efficiencies of only about 30%, PEMFCs exhibit significantly higher power conversion efficiencies of up to 60%. PEMFCs have not reached the commercial stage yet because they have not met the US Department of Energy's fuel cell commercialization targets of at least 5000 operating hours and a cost lower than $45 / kW in 2010 and $30 / kW in 2015. The main barrier to commercialization therefore originates from the short lifetime and relatively high cost of the current membrane materials, which include state-of-the-art Nafion® membranes. Intensive research has recently turned to nonperfluorinated hydrocarbon membranes, which can reduce membrane costs significantly. These membranes suffer, however, from an uncontrolled microstructure, which fails to balance high performance with long-term durability. The aim of this project is to address this primary challenge by designing novel membranes, based on nonperfluorinated hydrocarbon rotaxanes. We expect, that the switchable nature of the rotaxanes will be able to induce tunable properties of the membranes, and hence improve the performance of the membranes, which's nanostructures should be controllable interactively by the application of external stimuli.