Nanocomposites and nanomaterials

Photodielectric properties of nematic liquid crystal mixture with impurity fullerene C60 and supramolecular complex Li-TCNQ

Vovk V.E., Kovalchuk O.V.
Molecular Photoelectronics Department, Institute of Physics of the NAS of Ukraine. Prospect Nauky, 46, Kyiv-03039, Ukraine. 
E-mail: pochtavlad85@gmail.com 
In recent years, many authors have shown that addition of various impurities into a nematic liquid crystal (NLC) can greatly improve their properties. Many various groups of researchers used impurities of various types and structures. In most cases, these clusters have an ordered structure. It was assumed that such structures can be formed in these systems due to formation of bonds between molecules of impurity and NLC or among these impurities. The measurements of photosensitivity of these structures were carried out at two orientations of molecules, and cluster structure is interest for investigation, which was the primary goal of researches. Influence of orientation molecules on NLC properties such as dielectric spectra, photosensitivity was studied in this work.
The mixtures of nematic liquid crystal, molecules С60 with attached molecules of 1,8-diaminoctane (С60D) (3 wt.%) and molecules Li-TCNQ (5 wt.%) were obtained. The impurities were directly added into NLC, after which the resulting solution was stirred mechanically and with ultrasound. The research of these mixtures was performed by oscilloscopic method within the frequency range 10-1…106 Hz and room temperature in darkness and at illumination by the focused light of halogen lamps. Measurements were carried out with planar and homeotropic orientations of molecules where thickness of a composite layer within the range 20…23 m was obtained by introducing a Teflon film between the glass plates over the protecting electrode. Due to the low viscosity of the NLC-С60D composite, filling the cells was achieved via pressurizing this composite between the electrodes. The effect of influence of light was determined from the analysis of the attitude relation of values of a component complex dielectric constant measured at illumination up to those measured in darkness. On the basis of the received data and the analysis of dielectric spectra, the mechanisms of observable effects have been offered. The conductivity of nematic and isotropic phases at different orientation of molecules in a cell has been appreciated.