Refractive index engineering of transparent ZrO2–polydimethylsiloxane nanocomposites

Transparent ZrO2–polydimethylsiloxane (PDMS) nanocomposites with high refractive index were prepared by dispersing ZrO2nanoparticles in a PDMS matrix via ligand molecule engineering. The ligand molecule consists of a diamine head group that adsorbs strongly onto the ZrO2nanoparticles, and a siloxane tail group with a double-tailed structure that can be easily stretched within the PDMS matrix and yields a greater steric hindrance compared to single-tailed structure. The transmission electron micrograph shows that the designed Si-based ligand molecule has a role to play in keeping ZrO2nanoparticles fully-dispersed even after the ZrO2nanoparticles were transferred into the PDMS matrix. UV-vis spectra indicate that ZrO2–PDMS nanocomposite had a high transparency of 93.3% in the whole visible range. The refractive index of the ZrO2–PDMS nanocomposite could be varied from 1.39 to 1.65 simply by increasing the ZrO2 content from 0 to 20.8% v/v.