A pH-triggered reinforcement of transient network of wormlike micelles by halloysite nanotubes of different charge
[Display omitted] •Halloysite nanotubes induce up to a 30-fold increase of viscosity of semi-dilute solution of wormlike surfactant micelles.•The higher the charge of the nanotubes the higher their effect on the viscosity of oppositely charged wormlike micelles solution.•System has peculiar flow cur...
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Veröffentlicht in: | Journal of molecular liquids 2023-01, Vol.370, p.121032, Article 121032 |
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Sprache: | eng |
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•Halloysite nanotubes induce up to a 30-fold increase of viscosity of semi-dilute solution of wormlike surfactant micelles.•The higher the charge of the nanotubes the higher their effect on the viscosity of oppositely charged wormlike micelles solution.•System has peculiar flow curves with two separate shear thinning regions and a plateau between them.
Soft viscoelastic nanocomposites based on entangled linear wormlike micelles of cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride and aluminosilicate clay halloysite nanotubes with a surface charge triggered by pH were prepared and studied by rheometry, ξ-potential measurements, thermogravimetric analysis, and cryo-TEM. It was shown that the nanotubes induce an increase of viscosity, which can be attributed to their incorporation into the network of entangled wormlike surfactant micelles via the attachment of micellar endcaps to the surfactant double layer on the surface of the nanotubes. The junctions between the micelles and the nanotubes were visualized by cryo-TEM. The soft nanocomposites demonstrate peculiar flow curves with two shear thinning regions and a plateau between them. The two slopes were attributed to the orientation of the nanotubes (at lower shear rates) and then of the micellar worms (at higher shear rates) along the direction of flow. The intermediate viscosity plateau may represent a stable flow when all nanotubes are oriented, while the micellar worms are not. The nanocomposite system was shown to be pH responsive. Its viscosity increases by 30 times with increasing pH from 4 to 9, which was explained by increasing surface charge of the nanotubes favoring the interaction with oppositely charged WLMs. Such soft materials with easily triggered rheological properties are very promising for various applications. |
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ISSN: | 0167-7322 1873-3166 |
DOI: | 10.1016/j.molliq.2022.121032 |