Anisotropic water diffusion in nematic self-assemblies of clay nanoplatelets suspended in water.
Diffusion-weighted magnetic resonance imaging provides a vivid description of the little understood role played by interfacial interactions with macroscopic bodies in the cooperative self-assembly of clay nanoplatelets suspended in water. The interfacial interaction between hydrophilic glass walls and clay platelets in a Na-fluorhectorite gel can produce, for dilute gels, a face-to-wall anchoring of the platelets that leads to a uniaxial nematic order with platelet faces parallel to the walls but with randomly distributed normals of the faces. The application of a magnetic field perpendicular to the walls transforms this uniaxial order to an extended biaxial nematic order with orthogonal alignment between normals and the field. Moreover, for apolar walls, this face-to-wall anchoring is considerably hindered, and the uniaxial nematic order can be substantially disrupted.
de Azevedo
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Programa de Pós-Graduação em Ciência de Materiais and Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco, Brazil.
Engelsberg
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Fossum
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de Souza
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