Laponite as a rheology modifier of alginate solutions: Physical gelation and aging evolution

The rheological behavior of alginate and Laponite/alginate solutions was studied. It was observed that the Cross viscosity model successfully describes the steady-state shear behavior of this polysaccharide. The scaling behavior analyzed for the entangled regime is in good agreement with polyelectrolyte solutions (Ge∼cp3/2), with interactions generated between the alginate and the charged surfaces of the Laponite platelets. Therefore, the effect of Laponite as a rheology modifier is influenced by the alginate concentration. Higher alginate concentrations hindered the formation of the house of cards microstructure. Frequency sweep tests were performed to analyze the transition from solid-like to liquid-like behavior in a solid-like dominated domain. Soft physical gels were obtained at low alginate concentrations. The gel point was determined (1.65 wt.% of alginate and 2 wt.% of Laponite) through the Kramers-Krönig damping factor, and time sweep tests revealed the evolution of the storage (G′) and loss modulus (G″) as functions of the waiting time (tw). The growing elasticity revealed that Laponite/alginate solutions undergo aging.