Refractive Index Modulation by Photo-Fries Rearrangement of Main Chain-Type Aromatic Polyurethanes

Abstract

Aromatic polyurethanes were prepared from aromatic diisocyanates and dialcohol, and their photoreaction properties and concomitant refractive index change was investigated. Time-course UV–vis spectroscopy of the polyurethanes films under 254 nm irradiation showed clear spectral transition with an isosbestic point, indicating that selective photoreaction proceeded. FT-IR spectra of the irradiated aromatic polyurethanes films showed a consistent change to the targeted photo-Fries rearrangement. Ellipsometry revealed refractive index increase up to +0.0411 after the irradiation of the films for 60 min, presenting the good potential of aromatic polyurethanes as the functional moieties toward various optical materials that require photo-modulation of refractive index.