INVESTIGATION OF THE PHOTOINDUCED OPTICAL ANISOTROPY OF AZO-DYE MESOPHASES

The photoinduced optical anisotropy (POA) of novel aqueous azo dye sys tems which form chromonic mesophases upon addition of methanol or sodi um chloride was investigated. The phases were characterized between cr ossed polarizers. For further characterization rheological and hologra phic transient relaxation experiments were carried out. Distinctive di fferences in the hologram formation and decay were found for phases wh ich exhibit the same texture in polarization microscopy. The generated holographic gratings could be assigned to either photoinduced phase t ransitions or an alignment of optical axes. In the present study we co ncentrate on a comparison of phases with the same macroscopic birefrin gence; results are discussed in comparison with models in the literatu re.