Preparation of Titanium-silphenylene-siloxane Hybrid Polymers with High Refractive Index, Transmittance, and Thermal Stability

Vinyl-containing titanium-silphenylene-siloxane oligomers ( O1 , O2 , O3 , and O4 ) with different molar ratios of titanium to silicon were successfully synthesized in high yields by nonhydrolytic sol-gel reaction, and the obtained four oligomers were further crosslinked with methylphenyl hydro-silicone oil ( 4 ) to form corresponding polymers ( P1 , P2 , P3 , and P4 ) by hydrosilylation reaction. Their structures were characterized with spectroscopic characterization techniques including FTIR, 1 H-NMR, and Raman spectroscopy. The effect of titanium element on crosslinking behavior, thermal resistance, refractive index, transparency, thermal aging stability, glass transition temperature, and surface properties of the polymers were studied. Compared with titanium-free polymer P1 , the thermal resistance, refractive index, and thermal aging stability of titanium-silphenylene-siloxane polymers ( P2 , P3 , and P4 ) were significantly improved. The titanium-silphenylene-siloxane polymers achieved a high refractive index ( n = 1.580–1.584) and thermostability ( T 5d > 500 °C). In thermal aging, the polymers exhibited superior performances with high optical transparency (~90% at 450 nm) and exhibited high thermal stability (~84% at 450 nm after thermal aging at 150 °C for 120 h). These data indicate that the polymers have potential application in optical materials such as LED encapsulants.