Photoreversible refractive index change of [2.2]metacyclophan-1-ene in PMMA film

Photochromic [2.2]metacyclophan-1-ene in a PMMA (polymethylmethacryate) film reversibly changed the refractive index, which was estimated by ellipsometric analysis. For example, the refractive indexes of the open form and the photostationary state at 352 nm in PMMA films (10.6%) were 1.4934 and 1.4996 at 901.82 nm, respectively, and the variation (Δn) was 0.0062. The calculated refractive indexes of the open and closed forms were 1.744 and 1.859, respectively. The refractive index of the PMMA film containing a photochromic dye changed photoreversibly due the photochromic reaction between the open and closed forms of [2.2]metacyclophan-1-ene.