Novel lanthanidomesogens based on lanthanide nitrates carrying three 4-pyridone ligands having two alkoxy chains at the periphery were synthesized and their structure was assigned based on IR spectroscopy and elemental analysis. Their thermal stability was evaluated by TG analysis confirming that the decomposition starts at very high temperatures around 300°C. The liquid crystalline properties were investigated by using a combination of techniques: polarized optical microscopy (POM) and differential scanning calorimetry (DSC) and, for selected compounds, by variable-temperature powder X-ray diffraction. The new liquid crystal display a hexagonal columnar phase (Colh) between 63°C and 242°C, depending on the length of the alkyl chain. Dielectric spectroscopy on a wide frequency range was used to evaluate the dipolar relaxation processes. The emission properties of a mixture of E7 doped with a selected europium complex filled in a planar cell were investigated on changing the applied voltage, ranging from 0V up to 15V.
Polymer Dispersed Liquid Crystal (PDLC) films are composite materials consisting of LC droplets embedded in polymers. In order to decrease the switching voltage of these devices, we prepared PDLC films doped with single wall carbon nanotubes (SWCNTs). The mesomorphic properties of the films were investigated by polarizing optical microscopy (POM). The electrical characteristics have been investigated using a Broadband Dielectric Spectrometer in a frequency domain (0.01-107) Hz and a temperature range (280-350) K. Some key aspects of an optical model for the analysis of the coherent transmittance of PDLC - NP films are presented.
Polymer Dispersed Liquid Crystals (PDLC) are composite materials consisting of small liquid crystal (LC) droplets surrounded by a polymer matrix. Due to their relatively easy preparation and processing, the PDLC devices found many applications such as displays, architectural windows, energy control devices, projection displays, spatial light modulators, polarizers.
Carbon nanotubes (CNT) have excellent mobility and are suitable as doping nanoparticles in order to improve the electrically- controlled orientation of LC.
This paper presents the methods of preparation of PDLC doped with CNT. Experimental results are presented for the films obtained by solvent induced polymerization method, using polymethyl methacrylate and a nematic LC, E7. The obtained films are characterized by polarized optical microscopy, differential scanning calorimetry and electro-optical transmission.