Poly conductivity anisotropy

D. R. Gagnon, J. D. Capistran, F. E. Karasz, and R. W. Lenz, Conductivity anisotropy in oriented poly(p-phenylene vinylene), Polym. Bull. 72 293 (1984). 

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 . 

Poly(arylenevinylene)s based on naphthalene (JJ7) and thiophene (118, 119) have been reported. When naphthalene was substituted for benzene in the polymer structure, the resulting conductivity for the AsFs-oxidized polymer was 10 S/cm. Orientation of the polymer via stretch alignment has not been reported. The thiophene derivative, however, was stretch aligned (118) and doped with iodine and FeCl3. Conductivities of2700 were obtained with iodine-doped samples having elongation ratios of 6. The anisotropy of the conductivity was 35. 

In this section, the behaviour of the electrolytic expansion in conducting polymers, especially polyaniline and poly(o-methoxyaniline) (PMAN) are described, with discussion of the basic redox reaction of polyaniline, the dependence of the expansion ratios on oxidation levels, the kind of anions, strain, the pH of the electrolyte and anisotropy. 

T e orientation process also produces an increase of the DC conductivity [20], with stretched films showing a room temperature conductivity parallel to the chains of 3 x 10" S/cm, similar to the value found for Shirakawa poly acetylene [47], and a temperature independent anistropy of about 40. Above 200K the conductivity appears activated with an energy of activation of 0.4eV. This temperature dei ndence will be determined by the most difficult hops these are likely to be between chains. Thus, the temperature independent anisotropy can be explained simply by the smaller number of interchain hops in the... 

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