Photoinduced changes of absorption and circular dichroism in a chiral nematic phase containing a photochromic fulgide

Mesophases composed of a nematic mixture (ZLI1132) alone or with a chiral inductor (twisted nematic phase) were doped with a photochromic furylfulgide (FFU) and irradiated with visible and UV light. FFU shows great fatigue resistance and high repeatability of photochromic cycles in these media. Quantum yields for the photoconversions are very similar to values previously reported in solution. Beside from the photochromic changes in absorption spectra, a great and reversible circular dichroism change in the chiral nematic phase was observed in the visible absorption band of the cyclic isomeric form of FFU upon UV irradiation. This change is due to the mesophase-induced chiral absorption. The potential of this signal for information storage is discussed.