Synthesis and property of epoxy prepolymer and curing agent with high refractive index

An epoxy prepolymer with high refractive index, diglycidyl ether of thiodiphenol (DGETP), was synthesized by 4,4′-thiodiphenol and epichlorohydrin via a two-step method. The curing agent o-benzenedimethanethiol (OBDMT) was synthesized by thiourea method. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance were employed to characterize the structures of these resins. The cured product of DGETP and OBDMT was analyzed by differential scanning calorimetry, ultraviolet–visible spectrometer, and Abbe refractometer and compared with the property of traditional curing agent of methyl hexahydrophthalic anhydride (MHHPA) and ordinary bisphenol A diglycidyl ether epoxy prepolymer cured products. The lower curing temperature and glass transition temperature of DGETP than those of MHHPA can be mainly attributed to the strong rotation capability of thioether bond. The zero light transmittance region of DGETP/OBDMT curing adhesive (200–380 nm) was broader than that of the other three. The refractive index of DGETP/OBDMT was up to 1.654.