Carbomer microgels as model yield-stress fluids

Abstract

The review presents current research results for Carbopol-based microgels as yield-stress materials, covering three aspects: chemical, physical and rheological. Such a joint three-aspect study has no analog in the literature. The chemical aspects of Carbopol polymers are presented in terms of a cross-linking polymerization of acrylic acid, their molecular structure, microgel formulation, polyacid dissociation and neutralization, osmotic pressure and associated immense microgel swelling. The physical characterization is focused on models of the shear-induced solid-to-liquid transition of microgels, which are formed of mesoscopic particles typical for soft matter materials. Models that describe interparticle effects are presented to explain the energy states of microgel particles at the mesoscale of scrutiny. Typical representatives of the models utilize attributes of jamming dispersions, micromechanical and polyelectrolyte reactions. Selected relationships that result from the models, such as scaling rules and nondimensional flow characteristics are also presented. The rheological part presents the discussion of problems of yield stress in 2D and 3D deformations, appearance and magnitude of the wall slip. The theory and characteristics of Carbopol microgel deformation in rotational rheometers are presented with graphs for the steady-state measurements, stress-controlled oscillation and two types of transient shear deformation. The review is concluded with suggestions for future research.

From breakup to coiling and buckling regimes in buoyant viscoplastic injections

“…As shown, the data points can be well fitted with the lines corresponding to the HB model parameters (Jaworski et al. 2021). The model, fitted by the experimental data, has three parameters, i.e.…”

Producing shape-engineered alginate particles using viscoplastic fluids

“…It is unlikely that this shrinkage is due to diffusion of the Carbomer macromolecules out of the particles into the bath considering the diffusion time scale of Carbomer ( O (10 3 –10 4 ) s), 68 and the fact that the particles shrink considerably during the first few minutes of bath entry. In addition, comparing the alginate mesh size (≈ 10–100 nm depending on the polymer solution and gelation bath concentration 69 ) and the size of unswollen Carbomer macromolecules (average diameter ≈ 20–410 nm depending on the molecular weight 70 ) suggests that Carbomer diffusion is unlikely to happen. Instead, the decrease in the size of particles can be attributed to shrinkage of alginate after gelation.…”

Analysis of Carbopol And Triethanolamine Concentration in The Viscoplastic Properties of Aqueous Solution

“…Carbopol is an acrylic acid cross-linked polymer with high molecular weight, commonly used in water that presents HB behavior. Given its non-toxic characteristics, it is compatible with human and environmental activities and has been used in pharmaceutical and cosmetic products [5]. However, a neutralizing agent is necessary (TEA), initially as a fungicidal agent and secondly to make the mixture pH neutral (close to 7) since the aqueous solution of Carbopol has an acidic pH (around two or three).…”