Effect of Substitution on the Change of Refractive Index in Dithienylethenes: An Ellipsometric Study

• Published in: Advanced functional materials Vol. 14; no. 4; pp. 357 - 363
• Main Authors: Bertarelli, C., Bianco, A., D'Amore, F., Gallazzi, M. C., Zerbi, G.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2004; WILEY‐VCH Verlag
• Subjects: Ellipsometry; Photochromic materials; Refractive Index
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200304414

An ellipsometric study was carried out in order to investigate the photoinduced change of the refractive index (Δn) of a series of diarylethenes across the entire spectral range 260–1700 nm. This technique allowed examination of the influence of the resonance conditions on the refractive index. Changing the chemical design of diarylethenes by introducing electron‐donating or electron‐withdrawing substituents in 5,5′‐positions of thiophyene allowed derivation of some correlations between chemical structure and Δn. A strong donor substituent directly linked to the 5,5′‐position of the diarylethene moiety gave rise to an increase in the change of the refractive index. 1,2‐bis(2‐methyl‐5‐formyl‐3‐thienyl)perfluorocyclopentene phenyl hydrazone showed a large and stable Δn of 0.005 at 1.5 μm and appeared to be a good candidate for the development of telecommunication devices. The photoinduced change in refractive index (Δn) of a series of diarylethenes has been investigated by ellipsometry (260–1700 nm), allowing examination of the influence of the resonance conditions on the refractive index. The largest Δn value, 0.005 ± 0.001 at λ=1.5 μm, was found for 1,2‐bis(2‐methyl‐5‐formyl‐3‐thienyl)perfluorocyclopentene phenyl hydrazone (see Figure) embedded in poly(methyl methacrylate).