We report the design, fabrication, and measurement of high efficiency, compact 45° single air interface bends in low refractive index contrast waveguides in a low refractive index material system. Using standard microfabrication techniques, the bends are fabricated on silicon substrates using perfluorcyclobutyl (PFCB) copolymers, which feature a high glass transition temperature and low absorption loss. The measured 45° bends have a loss of 0.30±0.03dB/bend for TM polarization and 0.33±0.03dB/bend for TE polarization.