Estudo de propriedades ópticas de fases nemáticas biaxial e biaxial induzida

Abstract

In this study we investigated the phase of sequence ND-(NC +ND)-NC foreseen in the phase diagram proposed by Quist to a mixture of sodium dodecyl sulphate (SDS), decanol (DeOH) heavy water (D2O). Furthermore, we addressed a direct transition between discotic ND and calamitic NC nematic phases, without the biaxial nematic phase NB; between them, it was also reported in the literature from the mixture of sodium decyl sulfate (NaDS); DeOH and D2O. We also show the existence of a biaxial phase NB unreported in the literature, in a line of the diagram proposed by Quist as in the diagram proposed by Saupe. Thus, we used experimental techniques: optical microscopy, polarized light, digital image processing and optical conoscopy. In another moment, we studied the transitions phase NC -NB -ND by refractive index measurements, optical birefringence and digital image processing. This phase sequence was characterized from the point of view linear optics, based on the refractive index data. Finally, from a uniaxial discotic nematic phase, we provoked a induction in a biaxial nematic phase by material ow and thermal expansion in two mixtures. This effect produced a micellar reorientation which producted images similar to those assigned conoscopics biaxial nematic phase, and compared the results with the phase NB reported in the literature