Anisotropy, electrical

Such oriented composites should also have electrical anisotropy. Indeed, for the composite material with

sample amounts to 5 x 10 5 Ohm-1 cm-1 which is also below... 

Liquid crystals form a state of matter intermediate between the ordered solid and the disordered liquid. These intermediate phases are called mesophases. In the crystalline state the constituent molecules or ions are ordered in position and orientation, whereas in the liquid state the molecules possess no positional and orientational ordering. Liquid crystals combine to some extent the properties of both the crystalline state (optical and electrical anisotropy) and the liquid state (fluidity). 

The main differences between metallomesogens and organic liquid crystals are (i) an increase in electric anisotropy because of the high polarizability of metals ... 

The electronic properties are also modified by polymerization. Experimentally, the band gap decreases to less than 1.2 eV in the low-pressure orthorhombic phase [65], and experiments [66,88,108] and calculations [80,109-111] agree that the band gap should decrease with an increasing number of intermolecular bonds. (We note the possible exception of the high-pressure polymerized orthorhombic phase, as discussed above.) Calculations [85, 111] show that the rhombohedral phase should have a more three-dimensional band structure than the orthorhombic phase but still be a semiconductor. However, recent measurements by Makarova et al. [88] showed that oriented samples of the rhombohedral phase had an extremely large electrical anisotropy, larger than that of single-crys-... 

Aromatic hydrocarbon pentacene is important for application in OTFTs as it has superior field effect mobility, good semiconducting behavior, and stability [153], The chemical structure is shown in Fig. 6.10. Pentacene semiconductor films can be fabricated by sublimation in a vacuum deposition system. Optimization of the fabrication parameters, such as the substrate temperature and deposition rate, can yield a highly ordered pentacene film with improved device performance. Oriented films have optical and electrical anisotropies. 

The considerable electrical anisotropy of this salt is made still more evident on the room-temperature polarized infrared reflection spectra [30] (see also Chapter 6 and Fig. 1 of this chapter). In addition, these reflection spectra give a remarkably clear information on the existence of strong coupling between the quasi-one-dimensional electronic system and the symmetric ag vibrational modes of the TCNQ molecules. More precisely, under the effect of this coupling, these particular modes, which are normally Raman active but infrared nonactive, acquire an anomalous intense infrared activity together with an anomalous polarization [20,30,31]. 

For axially symmetric molecules having a permanent electric quadrupole moment 0, polarizability a, and electric anisotropy k, separated by the distance r , we have Jansen s formula" (in the absence of angular correlations) ... 

Macromolecule Mean length or Electric dipole moment Electric anisotropy ( 3 - 0(i)... 

From equation (21), the optically induced electric anisotropy results in the form ... 

This electric anisotropy is induced in atomic liquids by the translational fluctuations, which cause the atoms to re-group momentarily into assemblages of two, three, or more atoms (in general, multiple assemblages) which can undergo orientation by the external electric field." ... 

T. Nisisako, T. Torii, T. Takahashi, and Y. TaMzawa, Synthesis of monodisperse bicolored janus particles with electrical anisotropy using a microfluidic coflow system. Advanced Materials, 18, 1152—i-, (2006). 

It is hoped that in the near future suflBciently well defined crystals will be obtained which will permit us to investigate the possible electrical anisotropy of this most interesting, highly conducting material. 

T. Toth-Katona, A. Cauquil-Vergnes, N. Eber and A. Buka, Nonstandard electroconvection with Hopf bifurcation in a nematic liquid crystal with negative electric anisotropies, Phys. Rev. E 75(6), 066210/1-12, (2007). 

In streaming solutions, the chains become oriented parallel to the flow direction, with subsequent modification of physical properties. The birefringence, electrical anisotropy and light-scattering properties indicate such linearly extended chains, but in very concentrated solutions, or in the presence of electrolytes, they indicate the coiling up of these chains. 

The calculation is the same for an electric field, replacing H hy E = V/d, where V is the voltage applied across the nematic layer, and replacing Xa by a, the electrical anisotropy. 

Meanwhile, the perpendicular conductivity of the Mo-based PPCH503A and PBP503A polymers decreased by 10 -10 as expected. However, that of the Fe-based PPCH503A polymer showed a reverse trend, increasing by 70 times. Such a sample dependence of conductivity resulted in a range in electrical anisotropy (cT /o ) of 2-10 ... 

On the other hand, the electrical anisotropy gradually weakens with the increase of CB concentration because higher CB loading means that more CB particles staying in the matrix to form a better conductive network. When the CB concentration rises up to 8.1 vol%, the conductive network is so perfect that the anisotropic intensity reduces down to 1.12. 

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