Sulfur-Rich Polyimide/TiO2 Hybrid Materials with a Tunable Refractive Index

High refractive index (RI) polyimide/titania nanoparticle hybrid materials were synthesized and characterized in this study. The polyimide synthesis took place via the conventional polycondensation process following the preparation of poly(amic acid), and the nanoparticles were incorporated using an in situ sol-gel process. Thin films of the polyimide/titania nanoparticle hybrids were prepared by optimizing the coating conditions using a spin coater. Thermal imidization of the nanoparticle containing poly(amic acid) films on Si wafers was completed in a temperature-controlled drying oven under a N-2 atmosphere. Fourier transform infrared spectroscopy revealed the successful formation of inorganic bonds as well as imide linkages, and transmission electron microscopy results show well-dispersed nanocrystalline TiO2 nanoparticles of around 5 nm in the polymer matrix. Thorough optimization of the reaction time and concentration of TiO2 precursors enabled to achieve a titania content as high as 30% (wt). The RI of the resultant hybrid materials was found to be tunable according to the titania content, while the RI increased linearly with increasing titania content. A homogeneous hybrid material with a very high RI of 1.84 at 589 nm was achieved in this work for 30% (wt) TiO2.

Automated summary

High refractive index polyimide/titania nanoparticle hybrid materials were synthesized and characterized. The titania content in the hybrid materials was successfully tuned up to 30% by optimizing the coating conditions and reaction parameters. The refractive index of the hybrid materials increased linearly with increasing titania content.