Ta. Krentsel et al., IN-SITU X-RAY MEASUREMENTS OF LIGHT-CONTROLLED LAYER SPACING IN A SMECTIC-A LIQUID-CRYSTAL, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 304, 1997, pp. 463-469
The smectic-A phase of octylcyanobiphenyl (8CB) doped with a photosens
itive azo-compound has been reported to exhibit structural changes and
formation of periodic layers distortions upon exposure to low-level r
adiation. It is caused by changes in the smectic layer spacing trigger
ed by light-induced molecular photoisomerization of the dopant azocomp
ound. Our in-situ high resolution x-ray scattering study reveals that
the light irradiation controls the smectic spacing. The exposure to UV
light increases the layer spacing by as much as 0.5% (0.155 Angstrom
for the studied mixture of 8CB and diheptylazobenzene 7AB at T = 24.00
degrees C). Irradiation by Be-Ne laser at 633 nm causes the contracti
on of the layers.