Organic materials offer new electronic functionality not available in inorganic devices. However, the integration of organic compounds within nanoscale electronic circuitry poses new challenges for materials physics and chemistry. Typically, the electronic states in organic materials are energetically misaligned with the Fermi level of metal contacts. Here, we study the voltage-induced change in conductivity in nanoscale devices comprising a monolayer of polyelectrolyte macromolecules. The devices are fabricated using integrated shadow masks. Reversible switching is observed between conducting ( ON) and non-conducting ( OFF) states in the devices. The open design of our devices easily permits chemical modification of the polyelectrolyte, which we show has a pronounced effect on the ON - OFF switching. We suggest that the switching voltage ionizes the polymers, creating a conducting channel of electronic levels aligned with the contact Fermi level.