Large Photoinduced Refractive Index Changes of Transparent Polymer Films Containing Photoeliminable Diazo and Azido Groups

Abstract

We measured photoinduced refractive index changes of polymer films containing various compounds, such as R-diazoketone derivatives, azide derivatives, and others which induce the loss of nitrogen molecules during photoirradiation. PMMA films containing 20 wt % of 2-diazo-1-indanone (2DI) and -azidostyrene ( -AS) showed large refractive index changes of 0.015 during photolysis, keeping transparency throughout the entire visible region. The fact that the chemical structure of the substituents at R-position of the diazo group and hence the resonance effect do not affect the photoinduced changes in refractive indices much indicates the major contribution of the elimination effect of nitrogen molecules to the refractive index changes. Azide derivatives except for -AS showed small refractive index changes which may be related to the chemical structure of the photoproducts. Discussion is given on the estimation of the molar refraction and the contribution of the changes in electronic structure and in density to the refractive index of the systems.

Mechanisms of the refractive index change in DO11/PMMA due to photodegradation

“…However, starting above k 0 = 14 µm −1 (λ ≈ 450nm) the measured SRID and KK calculation begin diverging. Given that the difference is found to monotonically increase with wavenumber starting near k 0 = 14µm −1 , we propose that this difference is due to irreversible photodegradation of the polymer host, as the measured difference correlates with measurements of the refractive index change of neat PMMA when photodegraded [18,19,23,20,21,22].…”

A novel photobleachable polysilane copolymer for optical waveguide fabrication

“…However, these compounds had an absorption band in the visible wavelength region. Murase and Horie achieved transparency over the entire visible wavelength with a poly(methyl methacrylate) (PMMA) film doped with diazo and azido groups 5. In their system, the decrease of π ‐conjugation due to photo‐irradiation was used to change the refractive index.…”

Large Photoinduced Refractive Index Increase in Polymer Films Containing Phenylazide Maintaining Their Transparency and Thermal Stability

“…On the other hands, by using irreversible photochemical reactions such as photoelimination and photopolymerization, large refractive index changes of polymer films have been realized with transparency both before and after photoirradiation in a wide visible region. [10][11][12][13][14][15][16][17][18][19] Among them, Photoelimination brings about the changes not only in electronic structure of photoreactive compounds and also in the density of the polymer films, which leads to larger refractive index changes. 16,17 The refractive indices of the photoirradiated area decreased in many cases, however, the increases in refractive index of the photoirradiated area are necessary for some applications.…”

“…[10][11][12][13][14][15][16][17][18][19] Among them, Photoelimination brings about the changes not only in electronic structure of photoreactive compounds and also in the density of the polymer films, which leads to larger refractive index changes. 16,17 The refractive indices of the photoirradiated area decreased in many cases, however, the increases in refractive index of the photoirradiated area are necessary for some applications. In some cases, the presence of remaining doped reactants, which have not reacted in the films, may cause thermal or chemical instability in optical devices.…”

“…In general, polymer films containing a photoeliminable compound exhibit decreases in refractive index during the photoreaction as mentioned above, however the polymer films containing some azido derivatives did not decrease but increased their refractive indices by photoirradiation. 16,20 Moreover, since PAZ is volatile, we can remove unreacting PAZ from the non-irradiated area of the polymer films at a moderate condition, which gives not only large refractive index increase but also thermal stability on patterned polymer films.In the present study, we exhibited large refractive index increases in polymer films containing various concentrations of PAZ by photoirradiation and a postbake 203 …”