Investigations on ferroelectric liquid crystalline systems with the laser intensity modulation method
✍ Scribed by Norbert Leister; Dieter Geschke
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 274 KB
- Volume
- 9
- Category
- Article
- ISSN
- 1042-7147
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✦ Synopsis
Spatially resolved polarization and charge distributions have been investigated in sandwich cells of two ferroelectric liquid crystal side-chain polymers and a low molecular weight ferroelectric mixture. For measurements without external field, contributions to the distribution at the surface of the liquid crystal layer have been found for all three materials. These are attributed to nonvanishing polarization due to surface interaction of the molecules. For both polymeric materials there is a strong dependence of the shape of the measured pyrospectra on the sample temperature. This is attributed to changes in material parameters. In contrast to this, for the low molecular weight substance only minor changes are visible.
For an applied external electric field, additional contributions to the resulting distribution caused by charge layers and by polarization due to helix unwinding can be observed. Charge layers are located near the surface of the liquid crystal layer. Helix unwinding can be observed for the low molecular weight material at room temperature. One of the polymers which is in the glassy state at room temperature shows corresponding effects above its glass transition point.