Experiments probing internal interactions bring new questions about polyelectrolyte gels

Ionizable, crosslinked polymer networks called polyelectrolyte gels have been researched for more than 70 years in a wide range of settings from the extracellular matrix to personal care products. Often, findings for how solutions affect gel behavior must account for numerous environmental factors. This makes the materials tunable but also complex.

Wilcox et al. discussed the state of the art of polyelectrolyte gels, highlighting both recent advances and challenges ahead for the field. The review covers how a wide array of new experimental findings, including electrostatic, Donnan, and elastic osmotic pressures, are balanced in the current thermodynamic model of gels.

“It is amazing how matter interacts with energy and what we can learn by the results of those interactions, even at length scales not accessible to optical microscopy,” said author Svetlana Morozova. “As described in the review, these nanoscale properties have a profound impact on the functionality of gels on the bulk scale.”

In addition to scattering techniques, the group’s paper draws attention to rheological experiments that test the elasticity of materials and how that is linked to internal structure and interactions.

The group proposes future work to focus on interfaces, inhomogeneities and how they affect gels in biology.

“Biological polyelectrolyte gels are interesting puzzles to put together,” Morozova said. “Not only do they have a charged nature that allows them to have more interactions than neutral gels, but they are more rigid than many synthetic gels, so the physics becomes more complicated.”

Morozova aims to continue studying the properties of biological networks, such as self-assembled collagen networks and how interfaces change local gel behavior.

Source: “Fundamentals and mechanics of polyelectrolyte gels: Thermodynamics, swelling, scattering and elasticity,” by Kathryn G. Wilcox, Susan K. Kozawa, and Svetlana Morozova, Chemical Physics Reviews (2021). The article can be accessed at https://doi.org/10.1063/5.0048152 .