Synthesis and properties of a novel fluorine-containing alicyclic diepoxide

A novel fluorine-containing alicyclic diepoxide resin, the diglycidyl ether of bis(1,1,1,3,3,3-hexafluoropropyl)cyclohexane (CHEP), has been synthesized using benzene, hexafluoroacetone, and epichlorohydrin. The CHEPs, consisting of a mixture of 1,3- and 1,4-isomers, whose epoxy equivalent weights are 270 and 290, are liquids with viscosities of 5000 and 30 000 cP at 25 degrees C, whereas the 1,4-isomer CHEP is a solid resin. The liquid CHEPs show low refractive indexes of similar to 1.405 due to the high fluorine content of more than 43 wt %. They also show high optical transparency to UV because they are nonaromatic hydrocarbons. The CHEPs can be cured by heat or UV irradiation in the presence of curing agents. The cured resins show refractive indexes of less than 1.45, and a l-mm-thick film has a high transparency of more than 80%, which includes Fresnel's reflection loss at both sides of the film/air interfaces, at wavelengths from 0.5 to 1.6 mu m. The glass transition temperature is up to 53 degrees C, and tensile shear strength to quartz glass is more than 100 kg/cm(2).