Dichroism of Poly(Methyl Methacrylate) Thin Films Doped with Disperse Orange 11 Molecules

Abstract

We investigate the absorption spectra of poly (methyl methacrylate) (PMMA) thin films doped with Disperse Orange 11 (DO11) dye molecules which change under illumination with visible light. Dichroism measurements of the kinetics of the transmission changes at 472 nm at room and low temperatures (−60• C ± 2 • C) have been investigated. Our data show that the photoisomerisation reaction and the light-induced polar orientation depend on the molecular structure of the polymer. Simultaneous UV-visible spectroscopy at low temperature confirms the existence of two forms of DO11 molecules (keto and enol forms), which are responsible for the interaction with irradiating laser light and forming an anisotropic structure inside the PMMA/DO11 thin film.

Investigation of Dynamic Dichroism Properties of Disperse Orange 11 Molecules and Azo-Molecules Doped in Poly(Methyl Methacrylate) Thin Films: A Comparison

“…The explanation of the absorption behaviour illustrated in Fig. 3 is well documented in previous works of many authors, as well as our published work [9,11]. Figure 4 shows the result of calculation of the induced dichroism in the 1.5 µm thin film samples using Eq.…”

“…However, they also diminish as soon as the pump irradiation is cut off, manifesting the tendency of the polymeric systems towards the isotropic states of the dye molecule distributions within the polymer networks. These observations indicate that these changes are completely reversible, leading to the conclusion that keto ⇔ enol of DO11 or trans ⇔ cis of azo-based dyes were occurring in the guest-host polymeric thin films [9]. Table II summerises the dichroism measurements for all samples.…”

“…The role of the two processes is manifested in the polar alignment of dye molecules in the polymeric guest/host systems, which is responsible for the development of the dichroism signals in the samples [1][2]9]. However, the extent of dichroism signals is governed by the polar nature of the dyes as well as their volumes.…”

“…This average absorbance represents the isotropic absorption, which does not depend on the medium anisotropy, and it characterises only the relative concentration of trans isomers of the azo-based dyes, or the keto forms of DO11 molecules present in the samples [9]. The dichroic ratio (the order parameter) was computed from the recorded spectra as [10]:…”

Investigation of molecular alignment in poly(methyl methacrylate) polymeric thin films doped with Sudan III chromophore

“…The photodiode was connected to the electronic detection system. Two absorbances obtained; parallel (A ) and perpendicular (A ⊥ ) to the electric vector of the laser irradiation, and may by calculated from [17]:…”