Relaxation of holographic gratings in liquid‐crystalline side chain polymers with azo chromophores

Abstract

The relaxation of holographic phase gratings was examined to obtain some information about the involved photochemically induced changes. The studies were performed with statistical liquidcrystalline side group copolymers having different concentrations of the azobenzene dye. The formation of mesophases, which normally exist in the thermodynamic equilibrium, was prevented during the sample preparation by quenching the polymer films. Two relaxation processes were found in this glassy state of the polymers. The faster one could be described by a dispersive stretched exponential function and was attributed to relaxation processes which are related to the amorphous phase of the sample, while the slower one, corresponding to a single exponential process, correlates with the formation of light-induced liquid-crystalline microstructures. The latter are believed to be the main cause for the modulation of the refractive index.

Azobenzene‐Containing Polymers for Surface Relief Gratings

“…Diffraction gratings were recorded by using a previously described holographic set-up. [5,9] Influence of the Molecular Weight To investigate the influence of the molecular weight on the formation of surface relief gratings a series of polymers was synthesized. Within this series the molecular weight of the prepolymer was adjusted using ATRP.…”

An Investigation of the Photoinduced Changes of Absorption of High-Performance Photoaddressable Polymers

“…A corr (f,f)/L cos 2 f cos 2 fa xx sin 2 f cos 2 fa yy sin 2 fa zz (2) Remember that f is a rotation of the sample with respect to the direction of incidence and f is the rotation of the sample within the xy plane, around the z-axis. Here, the z-axis is normal to the substrate plane and the x-axis is defined by the polarization of the actinic light during photoalignment.…”

“…Following the arguments outlined above, only the data at the wavelength of maximum absorption as obtained from measurements at normal incidence were analyzed and fitted according to Equation (2). An example of the fitted curve is shown in Figure 5.…”

Von der Fläche ins Volumen – Materialkonzepte für optisch‐holographische Datenspeicher der Zukunft

“…[121] Dieser Effekt tritt ebenfalls bei einer reinen trans-cis-Isomerisierung in Gegenwart anderer mesogener Gruppen auf. [119,[122][123][124] Dafür müssen die Substituenten an den mesogenen Einheiten zur Bildung sterischer oder dipolarer Wechselwirkungen auf die Azobenzolseitenketten abgestimmt werden. Untersuchungen haben gezeigt, dass dieser "Nachbargruppeneffekt" nur für Gruppen derselben Polymerhauptkette auftritt.…”