The structure-property relationship in LAPONITE® materials: from Wigner glasses to strong self-healing hydrogels formed by non-covalent interactions

Rheology, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) analysis, zeta potential measurement, scanning electron microscopy (SEM), and micro-FTIR and absorbance spectroscopy were used to enlighten the controversial literature about LAPONITE® materials. Our data suggest that...

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Bibliographic Details
Published in:Soft matter 2019-02, Vol.15 (6), p.1278-1289
Main Authors: Becher, Tiago B, Braga, Carolyne B, Bertuzzi, Diego L, Ramos, Miguel D, Hassan, Ayaz, Crespilho, Frank N, Ornelas, Catia
Format: Article
Language:English
Subjects:
Biocompatibility
Cations
Crosslinking
Drug delivery
Drug delivery systems
Fourier transforms
Hydrogels
Inorganic salts
Ionic interactions
Light scattering
Molds
Photon correlation spectroscopy
Polyacrylate
Rheological properties
Rheology
Salts
Scanning electron microscopy
Self healing materials
Small angle X ray scattering
Sodium
Sodium phosphate
Thinning
Viscoelasticity
X-ray scattering
Zeta potential
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Summary:Rheology, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) analysis, zeta potential measurement, scanning electron microscopy (SEM), and micro-FTIR and absorbance spectroscopy were used to enlighten the controversial literature about LAPONITE® materials. Our data suggest that pristine LAPONITE® in water does not form hydrogels induced by the so-called "house of cards" assembly, but rather forms Wigner glasses governed by repulsive forces. Ionic interactions between anisotropic LAPONITE® nanodiscs, sodium polyacrylate and inorganic salts afforded hydrogels that were transparent, self-standing, moldable, strong, and biocompatible with shear-thinning and self-healing behavior. An extensive study on the role of salts in the gelification process dictates a trend that relates the valence of cations with the viscoelastic properties of the bulk material ( G ′ values follow the trend, monovalent < divalent < trivalent). These hydrogels present G ′ values up to 5.1 × 10 4 Pa, which are considered high values for non-covalent hydrogels. Hydrogels crosslinked with sodium phosphate salts are biocompatible, and might be valid candidates for injectable drug delivery systems due to their shear-thinning behavior with rapid self-healing after injection. Rheology, SAXS, and dynamic light scattering (DLS) analysis, zeta potential measurement, scanning electron microscopy (SEM), and micro-FTIR and absorbance spectroscopy were used to enlighten the controversial literature about LAPONITE® materials.
ISSN:1744-683X
1744-6848
DOI:10.1039/c8sm01965g