Structure formation and aging in different arrested states of Laponite dispersions have been investigated at the macro- and microscale. Covering a wide range of solid content and salt concentrations at different pH glasses, strong and weak gels with prevailing edge-to-face (EF) or face-to-face (FF) layer contacts were formed. Mechanical shear and squeeze flow rheometry were combined with diffusing wave spectroscopy and multiple particle tracking (MPT) microrheology. Strong attractive gels form much more quickly than weak gels, and particularly repulsive glasses. Gels with preferred EF contacts are stronger and are created more quickly than gels with prevailing FF contacts. Strong gels show little aging and exhibit a weak increase of G′ tα with α = 0.11 ± 0.03, higher α values are found for weak gels, and the strongest aging is observed in glasses. MPT data reveal structural refinement at the submicrometer length scale during aging for gels but not for glasses. Strong structural heterogeneity most pronounced at pH = 8.5 occurs during gel or glass formation, but at longer times, all arrested states appear homogenous at the 0.2 μm length scale. Finally, all arrested states exhibit power law frequency dependence G″ ω0.75 at high frequencies attributed to internal bending modes of layers.
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March 2018
Research Article|
March 01 2018
Macro- and microscale structure formation and aging in different arrested states of Laponite dispersions
M. Pilavtepe;
M. Pilavtepe
a)
1
Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology
, 76131 Karlsruhe, Germany
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S. M. Recktenwald;
S. M. Recktenwald
1
Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology
, 76131 Karlsruhe, Germany
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R. Schuhmann;
R. Schuhmann
2
Competence Center for Material Moisture, Karlsruhe Institute of Technology
, 76344 Karlsruhe, Germany
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K. Emmerich;
K. Emmerich
2
Competence Center for Material Moisture, Karlsruhe Institute of Technology
, 76344 Karlsruhe, Germany
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N. Willenbacher
N. Willenbacher
1
Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology
, 76131 Karlsruhe, Germany
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a)
Author to whom correspondence should be addressed; electronic mail: [email protected]
J. Rheol. 62, 593–605 (2018)
Article history
Received:
August 24 2017
Accepted:
February 05 2018
Citation
M. Pilavtepe, S. M. Recktenwald, R. Schuhmann, K. Emmerich, N. Willenbacher; Macro- and microscale structure formation and aging in different arrested states of Laponite dispersions. J. Rheol. 1 March 2018; 62 (2): 593–605. https://doi.org/10.1122/1.5001382
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