A conductivity anisotropy

The method has also been applied to PAni [53]. The plasticizer is a solvent of the polymer N-methylpyrrolidone (NMP), and the film to be stretched is not, or is very poorly, crystalline and may contain up to 20 wt% NMP. Tg decreases as the NMP content increases, down to 110°C heating and stretching swollen EB films above that Tg value produces X > 6, increased crystallinity (Fig. 11), and sizable orientation and anisotropic properties [27,99,100]. Such films, doped with HC1, show a conductivity anisotropy = 25 [99-101]. Contrary to what is observed with PPV, the mechanical properties of stretched PAni remain modest the Young s modulus is below 0.5 GPa [53]. 

Herold A., Conductivity anisotropy in arsenic pentafluoride-intercalated graphite. In Chemical Physics of Intercalation, Legrand A. P. (ed.), NATO ASI Series, Vol. 172 (1987), p. 3B. 

Among techniques used to characterize such LB CP films have been low angle x-ray diffraction, comparative transmission-mode and reflection-mode IR spectroscopy, near-edge X-ray absorption fine structure (NEXAFS), and of course, conductivities, determined by transfer of LB films onto special 4-electrode substrates. As expected especially for the LB CP films which include alternating non-conductive surface-active molecular layers, conductivities of such films are highly anisotropic. For example, the conductivity of Shimidzu et al. s poly(3-octadecyl 4-Me-pyrrole-3-carboxylate)/octadecane alternating layer film, described above, is 10 S/cm in-plane and 10 S/cm across the film, yielding a conductivity anisotropy of 10 . 

Although the dominant means to create a space-charge field within the interference pattern in liquid crystals is given by Eq. (2), it has been shown that there are other mechanisms to create a space-charge field. One is derived from the conductivity anisotropy and is known as the Carr-Helfrich effect [43,49] ... 

The electrical conductance shows a weaker concentration dependence above than below the CMC corresponding to a decrease in the equivalent conductance (Fig. 2.10). The transport number of the surfactant ion rises sharply at the CMC while that of the counterion may become negative. This as well as electrophoretic mobilities may yield information on micellar charge. At high concentrations, conductance anisotropies have been observed for flowing systems. This, as well as flow birefringence, is useful for the demonstration of nonspherical micelle shape. 

Rheological properties are particularly sensitive and for some solubilizates, such as a-methylnaphthalene, the solutions may become viscoelastic the appearence of viscoelasticity often depends on subtle effects in chemical structure29). Certain spectroscopic features are strongly influenced. Thus the H and 13C NMR line widths show large increases, the 81 Br quadrupole relaxation may be strongly affected and there may be the appearance of linear dichroism, birefringence and conductance anisotropy for flowing systems. 

Fig. 7a, b Average mass transfer coefficient as a function of a aquifer anisotropy ratio for several variances of the log-transformed hydraulic conductivity distribution b variance of the log-transformed hydraulic conductivity distribution where open circles represent numerically generated data and solid lines represent linear fits. All model parameter values are identical with those used in Fig. 6... 

Figure 12 (a) Temperature dependence of the longitudinal resistivity of (TMTSF)2PF6 obtained with the clamped contact technique. (From W. Kang, private communication, and O. Traetteberg, Thesis, Univ. Orsay, 1993.) (b) The conductivity anisotropy is temperature independent as long as the transverse motion remains incoherent. Data for (TMTSF)2PF6 under 12 kbar. (After Ref. 6.)... 

Fig. 22 Schematic self-assembled transverse-witlzin-parallel aligned structure of PS-6-P4VP(TSA)i.o(PDP)i.o supramolecules and the direct-current conductivity as a fimction of temperature. Presented also is the isotropic conductivity of a nonaligned sample (4). In the aligned case (3) the conductivity is increased, probably due to fewer domain boimd-aries, and the nanoscale conductivity anisotropy is manifestly present [155]...

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