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Delamination by Repulsive Osmotic Swelling of Synthetic Na-Hectorite with Variable Charge in Binary Dimethyl Sulfoxide–Water Mixtures

Title data

Dudko, Volodymyr ; Rosenfeldt, Sabine ; Siegel, Renée ; Senker, Jürgen ; Matejdes, Marian ; Breu, Josef:
Delamination by Repulsive Osmotic Swelling of Synthetic Na-Hectorite with Variable Charge in Binary Dimethyl Sulfoxide–Water Mixtures.
In: Langmuir. Vol. 38 (2022) Issue 35 . - pp. 10781-10790.
ISSN 1520-5827
DOI: https://doi.org/10.1021/acs.langmuir.2c00965

Abstract in another language

Swelling of clays is hampered by increasing layer charge. With vermiculite-type layer charge densities, crystalline swelling is limited to the two-layer hydrate, while osmotic swelling requires ion exchange with bulky and hydrophilic organic molecules or with Li+ cations to trigger repulsive osmotic swelling. Here, we report on surprising and counterintuitive osmotic swelling behavior of a vermiculite-type synthetic clay [Na-0.7](inter)[Mg2.3Li0.7](oct)[Si-4](O10F2)-O-tet in mixtures of water and dimethyl sulfoxide (DMSO). Although swelling in pure water is restricted to crystalline swelling, with the addition of DMSO, osmotic swelling sets in at some threshold composition. Finally, when the DMSO concentration is increased further to 75 vol %, swelling is restricted again to crystalline swelling as expected. Repulsive osmotic swelling thus is observed in a narrow composition range of the binary water-DMSO mixture, where a freezing point suppression is observed. This suppression is related to DMSO and water molecules exhibiting strong interactions leading to stable molecular clusters. Based on this phenomenological observation, we hypothesize that the unexpected swelling behavior might be related to the formation of different complexes of interlayer cations being formed at different compositions. Powder X-ray diffraction and Na-23 magic angle spinning-NMR evidence is presented that supports this hypothesis. We propose that the synergistic solvation of the interlayer sodium at favorable compositions exerts a steric pressure by the complexes formed in the interlayer. Concomitantly, the basal spacing is increased to a level, where entropic contributions of interlayer species lead to a spontaneous thermodynamically allowed one-dimensional dissolution of the clay stack.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: WOS:000885892800001
Institutions of the University: Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III > Chair Inorganic Chemistry III - Univ.-Prof. Dr. Jürgen Senker
Research Institutions > Central research institutes > Nordbayerisches Zentrum für NMR-Spektroskopie - NMR-Zentrum
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III
Research Institutions
Research Institutions > Central research institutes
Result of work at the UBT: Yes
DDC Subjects: 500 Science
500 Science > 540 Chemistry
Date Deposited: 19 Dec 2022 12:08
Last Modified: 29 Jan 2024 06:47
URI: https://eref.uni-bayreuth.de/id/eprint/73057