Intrinsic High Refractive Index Siloxane–Sulfide Polymer Networks Having High Thermostability and Transmittance via Thiol–Ene Cross-Linking Reaction

Siloxane-based polymer films obtained by the sol–gel process are often porous and exhibit low refractive indices. To address this issue, we have prepared two intrinsic high refractive index siloxane–sulfide polymer networks via the Piers–Rubinsztajn reaction and thiol–ene click chemistry based on readily available tetraethoxysilane (TEOS). Our siloxane–sulfide polymers consisting of aromatic groups and sulfur display enhanced thermostability with high T g (>120 °C) and T 5d (>320 °C) as compared to related materials. Such good thermal properties significantly expand their application as high thermostable optical materials. Besides, both flexible and colorless polymer films P1 and P2 exhibit high refractive indices of 1.625 and 1.665 at 546 nm, respectively. P2 also shows high refractive index of 1.648 at 1000 nm. Moreover, both siloxane–sulfide polymer films are uniform and homogeneous with high optical transmittance of 90% for wavelength ranging from 400 to 2000 nm. These data indicate that the new siloxane–sulfide polymers have potential application as optical materials such as antireflective coatings, encapsulation resin for the fabrication of LED, and the infrared transmitting materials.