Radiation effects on low refractive index, fluorinated methacrylate polymers for fiber cladding

The gamma radiation stability, optical properties, and mechanical properties of 1H, 1H, 3H-hexafluorobutyl and 1H, 1H-heptafluorobutyl methacrylate homopolymers and copolymers were determined and compared to poly(methyl methacrylate), PMMA. The aim of this study was to identify polymers for fiber cladding materials that exhibit improved optical radiation resistance and physical properties. Using (60)Co source, the samples absorbed 10 Mrads of gamma radiation at 0.04 Mrads/hr in an air environment. UV/Vis transmission spectra were obtained before irradiation, just after 10 Mrads, and regularly thereafter, to track recovery in transmittance. The glass transition temperatures, decomposition temperatures, refractive indices and flexural moduli were also obtained. Poly(heptafluorobutyl methacrylate) exhibited the greatest resistance to radiation induced discoloration and the lowest refractive index of the compositions tested. As the composition of the copolymers increased in hexafluorobutyl methacrylate concentration, both the radiation induced discoloration and the refractive index increased.