Osmotic swelling of sodium hectorite in ternary solvent mixtures : Nematic liquid crystals in hydrophobic media

Titelangaben

Mayr, Lina ; Amschler, Sonja ; Edenharter, Andreas ; Dudko, Volodymyr ; Kunz, Raphael ; Rosenfeldt, Sabine ; Breu, Josef:
Osmotic swelling of sodium hectorite in ternary solvent mixtures : Nematic liquid crystals in hydrophobic media.
In: Langmuir. Bd. 36 (2020) Heft 14 . - S. 3814-3820.
ISSN 1520-5827
DOI: https://doi.org/10.1021/acs.langmuir.0c00373

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Abstract

Swelling of clay minerals in organic solvents or solvent mixtures is key for the fabrication of polymer nanocomposites with perfectly dispersed filler that contain only individual clay layers. We here investigated the swelling behavior of sodium hectorite in different ternary solvent mixtures containing methanol, acetonitrile, ethylene glycol or glycerol carbonate with a minimum amount of water. We found that in these mixtures, less water is required than in the corresponding binary mixtures to set in complete delamination by repulsive osmotic swelling. A quantitative study of osmotic swelling in a particular ternary mixture resembles swelling behavior in pure water. At hectorite contents larger than 5 vol.-%, the separation of individual layers scales with ϕ-1. At this concentration a crossover is observed and swelling continues at slower pace (ϕ-0.5) below this value.