Photoinduced phase transitions and helix untwisting in the SmC* phase of a novel cinnamoyl-based liquid crystal |
| |
Authors: | Alexey Bobrovsky Valery Shibaev Věra Hamplová Miroslav Kašpar Vladimira Novotna Milada Glogarová |
| |
Affiliation: | 1. Faculty of Chemistry , Moscow State University, Leninskie gory , Moscow, 119992, Russia bbrvsky@yahoo.com;3. Faculty of Chemistry , Moscow State University, Leninskie gory , Moscow, 119992, Russia;4. Institute of Physics, Academy of Sciences of the Czech Republic , 182 21, Prague 8, Czech Republic |
| |
Abstract: | A photoinduced phase transition and helix untwisting in a new liquid crystal forming the SmC* phase were studied in detail. The compound consists of a cinnamoyl photosensitive fragment with C?=?C double bond capable of photoisomerisation and photocycloaddition. It was shown that ultraviolet (UV) irradiation (365 nm) induces an extreme decrease in phase transitions temperatures (SmC*–SmA*, SmA*–N*, N*–I). Vertically aligned samples in the SmC* phase cause selective light reflection in the visible spectral range. The light action results in a noticeable helix untwisting that causes a shift in the selective light reflection peak to the long-wavelength spectral region. The temperature dependence of spontaneous polarisation P s was measured and it was found that UV irradiation induces a decrease in the values of P s. Photo-optical phenomena taking place in the liquid crystal are attributed to the formation of photoproducts having low anisometry, which disrupts mesophases. |
| |
Keywords: | photoinduced phase transition SmC* phase helix untwisting |
|
|