to cause it to remain in the area where the lubrication is needed, rather than migrating away by spreading and forming a new surface. As a result, contamination of other components and equipment, which do not require a lubricant, is avoided. The high surface tension of PPEs, therefore, makes them useful in lubricating electronic contacts. Polyphenyl ether lubricants have a 30-year history of commercial service for connectors with precious and base metal contacts in telecom, automotive, aerospace, instrumentation and general-purpose applications. In addition to maintaining the current flow and providing long-term lubrication, PPEs offer protection to connectors against aggressive acidic and oxidative environments. By providing a protective surface film, polyphenyl ethers not only protect connectors against corrosion but also against vibration-related wear and abrasion that leads to fretting wear. The devices that benefit from the specialized properties of PPEs include cell phones, printers, and a variety of other electronic appliances. The protection lasts for decades or for the life of the equipment. Optics Polyphenyl ethers (PPEs) possess good optical clarity, a high refractive index, and other beneficial optical properties. Because of these, PPEs have the ability to meet the rigorous performance demands of signal processing in advanced photonics systems. Optical clarity of PPEs resembles that of the other optical polymers, that is, they have refractive indices of between 1.5 and 1.7 and provide good propagation of light between approximately 400 nm and 1700 nm. Close refractive index (RI) matching between materials is important for proper propagation of light through them. Because of the ease of RI matching, PPEs are used in many optical devices as optical fluids. Extreme resistance to ionizing radiation gives PPEs an added advantage in the manufacture of solar cells and solid-state UV/blue emitters and telecommunication equipment made from high-index glasses and semiconductors. High-temperature and radiation-resistant lubricants PPEs, being of excellent thermo-oxidative stability and radiation resistance, have found extensive use in high temperature applications that also require radiation resistance. In addition, PPEs demonstrate better wear control and load-carrying ability than mineral oils, especially when used in bearings. PPEs were developed for use in jet engines that involved high speed-related frictional temperatures of as high as . While the use of PPEs in lubricating jet engines has somewhat subsided due to their higher cost, they are still used in some aerospace applications. PPEs are also used as base fluids for radiation-resistant greases used in nuclear power plant mechanisms.