Insight into the aqueous Laponite® nanodispersions for self-assembled poly(itaconic acid) nanocomposite hydrogels: The effect of multivalent phosphate dispersants

Hypothesis: We hypothesize, that physical network between Laponite (R) nanoparticles and high molecular weight polyelectrolyte formed by mixing of Laponite (R) nanodispersion (containing multivalent phosphate dispersant) and polyelectrolyte solution is strongly influenced by the type and content of dispersant, which forms electric double layer (EDL) closely to the Laponite (R) edges. Thus, optimum dispersant concentration is necessary to overcome clay-clay interactions (excellent clay delamination), but should not be exceeded, what would result in the EDL compression and weakening of attractions forming clay-polyelectrolyte network. Thus, deeper investigation of Laponite (R) nanodispersions is highly demanded since it would enable to better design the self-assembled clay-polyelectrolyte hydrogels. Experiments: To study clay interparticle interactions in the presence of various multivalent phosphates, complementary methods providing wide nanodispersion characterization have been applied: zeta potential measurement and SAXS technique (electrostatic interactions), oscillatory rheology (nanodispersion physical state) and NMR experiments (ion immobilization degree). Findings: It was found that multivalent phosphates induce and tune strength of clay-polyelectrolyte interactions forming hydrogel network in terms of varying EDL on the Laponite (R) edges. Moreover, phosphate dispersing efficiency depends on the molecular size, chemical structure, and valence of the anion; its potential as efficient dispersant for hydrogel preparation can be evaluated by estimation of anion charge density. (C) 2021 Elsevier Inc. All rights reserved.