We prepared a copolymer of the maleic anhydride with styrene, to which a colored structure designated for the functionalization was added. The new polymer was used to prepare reverse-mode PDLC films. Reverse-mode PDLC are designed for applications where it is important that the failure of the device is a transparent state, rather than a scattering one. We obtained reverse-mode PDLC using a nematic liquid crystal with negative anisotropy (Delta) (epsilon) <0, LCM 3141 (NIOPIK), and we measured the optical transmission of the film. The system was switched from OFF-transparent state to the ON-scattering one, by a sufficiently small voltage, but with a rather low contrast ratio.
We obtained polymer dispersed liquid crystal (PDLC) films using a nematic liquid crystal E7 and polymethyl methacrylate by the Solvent Induced Phase Separation method. Using the Thermally Stimulated Depolarization Current method we determined the clearing point of the pure liquid crystal and the PDLC films. The glass transition temperature of the PMMA matrix has also been determined. The result have been compared with those obtained by Differential Scanning Calorimetry. During the TSDC measurements we registered the optical transmission as a function of temperature, thus the thermal switch operation being demonstrated.
We present the experimental results concerning hybrid optical bistable devices without resonant cavity using as electro-optic modulators a nematic liquid crystal cell and a polymer dispersed liquid crystal film. Bistable operation was studied for different control voltages and multistable behavior was studied for the polymer dispersed liquid crystal film as a function of the control voltage frequency.
The electrooptical properties of some SSFLC devices with high spontaneous polarization liquid crystals are presented. The switching time was determined as function of electric field strength and a.c. frequency. Using the switching time the rotational viscosity (gamma) $curly phi was determined. The results are explained by considering the spectacular molecular relaxation, known as Goldstone mode. The surface stabilized ferroelectric liquid crystal (SSFLC) devices offer memory (bistable) capability, fast response speed and sharp threshold and have a variety of applications in electronics.
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