Steady and Oscillatory Shear Flow Behavior of Different Polysaccharides with Laponite®

Abstract

The rheological behavior, in terms of steady and oscillatory shear flow, of Laponite® with different polysaccharides (alginate, chitosan, xanthan gum and levan) in salt-free solutions was studied. Results showed that a higher polymer concentration increased the zero-rate viscosity and decreased the critical strain rate (Cross model fit) as well as increasing the elastic and viscous moduli. Those properties (zero-rate viscosity and critical strain rate) can be a suitable indicator of the effect of the Laponite® on the shear flow behavior for the different solutions. Specifically, the effect of the Laponite® predominates for solutions with large critical strain rate and low zero-rate viscosity, modifying significantly the previous parameters and even the yield stress (if existing). On the other hand, larger higher polymeric concentration hinders the formation of the platelet structure, and polymer entanglement becomes predominant. Furthermore, the addition of high concentrations of Laponite® increases the elastic nature, but without modifying the typical mechanical spectra for polymeric solutions. Finally, Laponite® was added to (previously crosslinked) gels of alginate and chitosan, obtaining different results depending on the material. These results highlight the possibility of predicting qualitatively the impact of the Laponite® on different polymeric solutions depending on the solutions properties.

Laponite Composites: In Situ Films Forming as a Possible Healing Agent

“…In contrast, the other formulation was characterized by a bigger size and a Z potential closer to zero, which probably meant that some particles agglomerated, creating a resistance to flow and therefore obtaining higher values of viscosity. Figure 3 b displays the small-amplitude oscillatory flow results [ 38 ], evaluating the elastic and viscous modulus (G′ and G″, respectively) vs. frequency-flow (ω). Both optimal fluids demonstrated the same viscoelastic behavior; however, the elastic modulus predominated at all evaluated frequencies (G′ > G″) mainly due to the entanglement between biopolymers and clay in the dispersions [ 39 ].…”

Does the Freeze–Thaw Technique Affect the Properties of the Alginate/Chitosan Glutamate Gels with Posaconazole as a Model Antifungal Drug?

“…The obtained results demonstrated that all investigated hydrogels and cryogels exhibited shear-thinning behavior, which is characterized by a reduction in the viscosity with an increase in the shear stress gradient and indicates their non-Newtonian nature. This phenomenon is typical to polymer solutions and expresses the character of a pseudo-plastic fluid where the viscosity is decreased under the influence of shear [ 28 ]. The shear-thinning phenomenon is an important parameter for topical application—it enables the thin gel layer formation on the skin during application [ 29 ].…”

Poly(vinyl alcohol)/Pullulan Composite Hydrogels as a Potential Platform for Wound Dressing Applications

“…In the presence of clay (Figure 4b), the PVA-PVA interactions are slowly pertur The rheological behavior of entangled polymer solutions is not significantly affected by the presence of Laponite ® RD, because the chain entanglements hinder the formation of the platelet structure [40]. However, the addition of clay to polysaccharide-based systems determines qualitative changes in the flow behavior and mechanical spectra [41,42].…”

“…The manifestation of attractive and repulsive interactions between particles can lead to arrested states (either attractive gel or repulsive glass), generating a variety of rheological behaviors, from quasi-Newtonian to viscoelastic and shear thinning fluids [43]. The rheological behavior of entangled polymer solutions is not signifi by the presence of Laponite ® RD, because the chain entanglements hinder of the platelet structure [40]. However, the addition of clay to polysacchar tems determines qualitative changes in the flow behavior and mechanical s It was also shown that the structural state of Laponite ® RD dispersions de concentration and ionic strength [38,43].…”