Magnetic-field-induced nematic-nematic phase separation and droplet formation in colloidal goethite.
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Publication date
2011
Authors
van den Pol, E
Verhoeff, A.A.
Lupascu, A.
Diaconeasa, M. A.
Davidson, P.
Dozov, I
Kuipers, B.W.M.
Thies - Weesie, Dominique
Vroege, Gert Jan
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Article
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Abstract
We demonstrate the suitability of polarization microscopy to study the recently discovered (parallel) nematic-(perpendicular) nematic phase separation. This novel type of phase transition is induced by applying an external magnetic field to a nematic liquid crystal of boardlike colloidal goethite and is due to an interplay between the intrinsic magnetic properties of goethite and the collective effect of liquid crystal formation. It is shown that the intense ochre colour of goethite does not preclude the use of polarization microscopy and interference colours, and that dichroism can give valuable qualitative information on the nature of the phases, their anchoring and their sedimentation and order parameter profiles. We also apply these techniques to study 'nematic-nematic tactoids': nematic droplets sedimenting within a nematic medium with mutually perpendicular orientations.
Keywords
ferric hydroxide, iron derivative, microsphere, mineral, article, birefringence, chemistry, crystallization, devices, liquid crystal, magnetism, methodology, phase transition, polarization microscopy, surface property, synthesis
Citation
van den Pol, E, Verhoeff, A A, Lupascu, A, Diaconeasa, M A, Davidson, P, Dozov, I, Kuipers, B W M, Thies-Weesie, D M E & Vroege, G J 2011, 'Magnetic-field-induced nematic-nematic phase separation and droplet formation in colloidal goethite.', Journal of Physics: Condensed Matter, vol. 23, no. 19, pp. 194108/1-194108/10. https://doi.org/10.1088/0953-8984/23/19/194108