Halloysite micropatterning: Similar to nematic liquid crystals ordering, halloysite nanotubes can orient themselves along a common axis. The accumulation of tubes from an isotropic centre to the circumference increases the tubes concentration beyond a critical one governed by Onsager’s theory for orientation of highly charged nanorods. The alignment is enhanced by higher concentrations, temperature, higher surface charge and length of the tubes. Suchs o-called “coffee ring” effect for halloysites was extended in applications forforming periodic rings along the length of glass capillary tube and micropatterns onto solid supports as was first demonstrated by M. Liu. Another application is drying of halloysite aqueous dispersion dropped onto small metal balls. Halloysites self-assemble into concentric barriers with periodicity of 0.1-0.2 mm and height of 2-5 mkm. One can use systematically place balls which confine the drying allowing for designed halloysite micropatterns, reminding interference of waves. Such micropatterns allowed for selective adsorption of aligned fibroblast cells along the nanotubes' orientation. Self-assembly on biological surfaces: Halloysite self-assembly may be linked to surface irregularities with positioning driven by capillary forces and final fixation in dry state; it found an interesting applications in halloysite hair coating. When hair is exposed for aqueous halloysite dispersion and then dried, one is getting stable 4-5 mkm thick multilayer nanotube coating. Pickering emulsion for spill oil bioremediation and catalysis: Halloysites can also assemble on an oil-water interface. Halloysites, both pristine and with surface hydrophobization, form oil-water Pickering microemulsions. Clay nanotubes positioned laterally on the oil-water interface are reducing the surface tensions and stabilizing the emulsion droplets. Pickering microemulsions with halloysite may be used in biphasic catalysis and spill petroleum bioremediation. The petroleum/water interface is roughened and microorganisms (Alcanivorax borkumensis, alkanotrophic bacteria widely distributed in marine environments) added for oil degradation are better attached to such oil droplets.

Self-assembly approach in halloysite nanotube composites

255th National Meeting (2018)

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