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• High refractive index polyimides with as high as more than 1.8 of RI value were developed. • Solubility was greatly improved realizing the use of easy processing method. • PI showed high-low-high cycles of RI in film state under redox condition. Soluble high refractive index polyimides have extensive applications in optical devices due to their ease of processing and versatility. In this work, selenide-containing polyimides were designed and synthesized via amine-dianhydride polycondensation. Two selenide containing diamines, e.g. bis(3-trifluoromethyl-4-aminophenyl)selenide (BTFAPS) and bis(4-aminophenyl)selenide (BAPS) were reacted with 4,4′-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) for the preparation of selenide containing polyimides. Comparison with its oxygen and sulfur counterparts, the selenide-containing PIs have better solubility, higher refractive index, and can bring redox responsiveness. This is due to the trifluoromethyl base, which possesses a large free volume, and the selenium element, which has a higher molar refraction and redox activities than even sulfur. Various techniques, such as nuclear magnetic resonance, gel permeation chromatography, Fourier transformed infrared spectroscopy and wide angle X-ray diffraction were used for characterizing the polymers structure. Differential scanning calorimetry, thermogravimetric analysis, ultraviolet-visible spectroscopy, spectroscopic ellipsometry and X-ray photoelectron spectroscopy were used to characterize the properties of the polymers. [ABSTRACT FROM AUTHOR]