Abstract
In order to improve our understanding of the mechanisms involved in the electrooptical effects of liquid crystal—polymer composites, and to identify the relevant parameters of these complex systems, we have investigated the influence of the chemical nature of the polymer surface on the anchoring of the liquid crystal. Our method consists in removing the liquid crystal from the composite by dissolution followed by supercritical drying of the solvent. The surface of the polymer is then modified by different reagents and the liquid crystal is reintroduced to the cell. Comparison of the results shows that for a cyanobiphenyl liquid crystal, fluorinated or hydroxylated chemical moieties on the surface of the polymer induce a stronger anchoring than alkyl moieties. This phenomenon seems to be due to the enhanced chemical compatibility between the liquid crystal and the surface of the polymer in the case of alkyl moieties. Finally, the study has shown that a reduction of anchoring of the liquid crystal is responsible for a decrease in driving voltage, rise time and hysteresis and an increase in decay time and off-state transmission.
Published Version
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