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A present chapter is focused on remarkable dielectric, electro-optical and micro-structural peculiarities of LC-CNTs dispersions, their correlation and mutual influence. It is mainly based on authors' original results obtained within recent years. The structure of this chapter is the following. The introductory part (section 1) gives short introduction to LC-CNTs composites and elucidates benefit of combination of LC and CNTs. It also outlines a field of questions further considered. A section 2 gives details of our samples and experimental methods. The next three sections correspondingly consider dielectric, electro-optical and structural peculiarities of LC-CNTs composites. Each of these topical sections starts with a short review and lasts with the authors' original results. The final, conclusion part (Section 6), summarizes most interesting properties of LC-CNTs suspensions, their application perspectives and mention some exciting problems for further investigations. www.intechopen.com Liquid crystal dispersions of carbon nanotubes: dielectric, electro-optical and structural peculiarities 453 power of 150 W. The concentration of CNTs, c, was varied in the range 0-2 wt %. Doping of CNTs has not influenced essentially the phase transition temperatures of LC-CNTs composites. 2.4 Cells The cells for electro-optical and dielectric measurements were made from glass substrates containing patterned ITO electrodes and aligning layers of polyimide. The polyimides AL2021 (JSR, Japan) and SE5300 (Nissan Chemicals, Japan) were used for homeotropic alignment of LC EBBA, MLC6608 and MLC6609, while the polyimide SE150 (Nissan Chemicals, Japan) was utilized for planar alignment of LC 5CB. The polyimide layers were rubbed by a fleecy cloth in order to provide a uniform planar alignment of LC in either fieldon state (EBBA, MLC6608 and MLC6609) or a zero field (5CB). The cells were assembled so that the rubbing directions of the opposite aligning layers were antiparallel. A cell gap was maintained by the glass spacers of appropriate size (16 m, if not otherwise stated). Finally, these cells were filled capillary with neat or CNTs doped liquid crystals heated to isotropic state. In some dielectric measurements the cells without alignment layers were utilized. The structure of LC-CNTs composites was monitored by observation of the filled cells placed between crossed polarizers, both by naked eye and in an optical polarizing microscope. 2.5 Electro-optical measurements The electro-optical measurements were carried out using the experimental setup described in (Koval'chuk et al., 2001a). The cell was set between two crossed polarizers so that the angle between the polarizer axes and the rubbing direction was 45°. The sinusoidal voltage 0-60 V (at frequency f=2 kHz) was applied to the cell. The voltage was stepwise increased from 0 to 60 V and then decreased back to 0; the total measuring time, i.e., time of voltage application, was about 1 min. The transmittance of the samples was calculated as =(I out /I in)*100%, where I in and ...

At U<1 V nearly the entire voltage in liquid crystals (LC) and in solutions of dyes in LC is applied to the near-electrode regions. In this range of voltages, the Schottky emission through a dielectric layer is the electric current flow mechanism transport. A thin (several nanometres) dielectric layer is formed through adsorption on the electrode of not only ions, but also neutral impurities. According to estimates, the concentration of such molecules in pure LC may much exceed that of ions. It is demonstrated experimentally that the barrier controlling the charge transport lies at the anode and characterizes the ionization of LC molecules. Similarities and distinctions between the observed tunnel charge transport in dielectric liquids and the Schottky effect in solids are analysed. It is shown that the low-frequency dielectric dispersion is caused by voltage redistribution. Comparison of the parameters characterizing the carrier transport with those of the relaxation processes in the diffusion region of the electric double layer shows that long-term near-electrode processes are controlled by charge transport across the electrode-LC interface.

The multifractal description of rough surfaces is discussed and the mechanisms for generation of fractal and multifractal height distributions of inhomogeneities for rough surfaces are simulated. The original technique for estimating the spectrum of singularities is proposed for the study of these distributions.

A B S T R A C TWe present a simple and effective approach for dispersion of carbon nanotubes (CNTs) into

Effects of induced steric hindrance on the dielectric behavior and H bonding in the supercooled liquid and vitreous alcoholThe effect of increasing ͑by more than one order of magnitude͒ of the conductivity of glycerine under the action of a low-frequency electric field (10 Ϫ4 -10 Ϫ3 Hz) and heating is discovered and investigated. The transition into the high-conductivity state is accompanied by formation of asymmetric double electric layers at the electrodes. Parameters of the electric barrier at the interface are determined. For example, for the sample with thickness 18 m at the temperature 325 K, the height of the potential barrier is 0.4 V, the thickness is 2.1 nm, the concentration of ionized centers is 3ϫ10 26 m Ϫ3 . The transition into the more conductive state can be induced by desorption of ions from the electrode surface. The properties of glycerine are investigated for the both low and high-conductive states by low frequency dielectric spectroscopy. The dispersion of components ⑀Ј and ⑀Љ of the complex dielectric permittivity for the both states is described by the Debye equation modified by Cole-Cole. The dielectric relaxation time and the thickness of the double electric layer W C -C , where the redistribution of charges takes place, are measured. The transition into the high-conductivity state is characterized by the decreasing ͑more than one order͒ of , its activation energy and W C -C . Comparison of the obtained data with the data for the liquid crystal mixture 1282 suggests that the dispersion of ⑀Ј and ⑀Љ is induced by redistribution of charges between the bulk and the interface.

Vacuum ultraviolet(VUV) irradiation (wavelength 147 nm) of siloxane polymers in the presence of air was studied using ATR FTIR and XPS spectroscopy. The ATR FTIR study revealed the formation of CO and OH groups in the surface layer depending on irradiation time and air pressure. The concentrations of CO and OH groups level off with the increase of irradiation time and pass through the maximum value with the increase of pressure in the range of 0.1-100 torr. The XPS study of irradiated polysiloxane films demonstrated that intermolecular crosslinking via oxygen atoms also takes place on the polymer surface. The concentrations of the most important oxygen species 0 and 03, produced by VUV photolysis of air and coming to the polymer surface were calculated for the air pressure range 0 .1-100torr. The photooxidation mechanism for siloxane polymers under VUV irradiation in air has been proposed.

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