Generation of charge carriers and formation of antisymmetric double electric layers in glycerine

Abstract

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.

Method and estimation of parameters of dense part of double electrical layer at the interface electrode-solution of the dye in liquid crystal

“…It follows from the table that the difference in the n value for each barrier is smaller than that observed for the values of the barrier height and thickness of the near-electrode layer W. In contrast to glycerol [8], it was difficult to estimate the concentration of molecules in the near-electrode area, because a mixture of liquid crystals was used, and it was not known what part of the total amount of the molecules in solution comprise the dye molecules in near-electrode area. However, based on comparison of the n values for the structure studied in this work with the results of [8], we can assume that almost all the molecules of the near-electrode layer are ionized. The main reason that leads to this effect is rather high value of electric field in the dense part of DEL.…”

“…As a result of this analysis, the value R 2 − C S was estimated. Like to the case of glycerol [8], it reaches tens of MOhm, which by more than 5 orders of magnitude exceeds the resistance of the sample bulk part. Because these structures is two-barier, one can foresee that the series resistance for each barrier is the resistance of another barrier providing a current flows in the forward direction.…”

“…Formation of barriers with different parameters near each electrode was first realized by us in glycerol [8] through a long-term (several hours) action of direct electric field at the temperature 340 K. Obtained in these samples were the CVC asymmetric as to the direction of electric field, and evaluated were the barrier parameters (height, thickness and concentration of ionized states). Unfortunately, this method to form different parameters of DEL could not be used for LC.…”

The Peculiarities of Photopolymerization in the Composite “Pre-polymer–TiO2Nanoparticles”

“…The high values of permittivity ðe 0 > 10 5 Þ in the low frequency region might be caused by the non-uniform distribution of electrical field, because of blocking the electro-chemical processes of charge exchange at the interfaces [20,22]. Assuming that electric field is applied mainly to anode [20,22] and taking into account the approximation made in References [23,24] one can calculate thickness of the near-electrode charge exchange layers, d e :…”

Effect of magnetic nanoparticles with various geometrical shapes on morphology and dielectric properties of nanodispersions of nematic liquid crystal in polymer matrix

“…The reason for the frequency dependence of ε' may be a complex process of polarization of PDLC as a heterogeneous medium. In this case, one should take into account not only the individual droplets of liquid, but also their interaction under the influence of an electric field [11]. It is important that for nano-PDLC the process of mutual polarization is pronounced significantly clearer than in the case of micro-PDLC.…”