Dielectrics, Anthraquinone

Recently, the surface tensor model has been used together with the dielectric continuum model to calculate the orientational order parameters of solutes in nematic solvents [8,9,27], Figure 2.32 shows the theoretical results for anthracene and anthraquinone in nematic solvents with different dielectric anisotropy. Considering only the surface tensor contribution, positive Szz and Sxx and negative are obtained, with Szz > Sxx > Syy. This corresponds to what could be expected on the basis of the molecular shape the long axis (z) is preferentially aligned with the director, and the normal to the... 

Figure 2.32 Order parameters calculated for (a) anthracene and (b) anthraquinone dissolved in nematics with different dielectric anisotropy [9]. For the case Ae > 0, the results obtained in the absence of induction effects are also shown (dotted line). The temperature dependence of the dielectric anisotropy is taken into account, with the values eNI = 10.2, AeN/ = 8 and eNI = 5.2, AeN/ = —0.5 for the two cases at the nematic-isotropic transition. Atomic charges in absolute value greater than 0.1 are shown (in e units). The y axis is perpendicular to the molecular plane.

For the determination of anthraquinone, added as a stabilizer in capacitor dielectrics (using chlorinated diphenyls, chlorinated naphthalenes and mineral oils as impregnants) a solvent consisting of a 3 2 mixture of chloroform and methanol with magnesium chloride and hydrochloric acid was able to dissolve all materials used.< ) Owing to the presence of the strong acid, the reduction of anthraquinone is shifted to potentials near 0 0 V. At these potentials the waves of the chlorinated products do not interfere. 

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