Osmotic Swelling Behavior and Structure of Ionic Microgel Mixtures

Microgels are soft, compressible colloidal particles composed of crosslinked polymer networks. When dispersed in solution, microgels absorb solvent and can acquire charge by dissociation of counterions. Importantly for applications (e.g., drug delivery, biosensing), particle swelling responds to environmental changes (e.g., temperature, pH, concentration) and interparticle interactions. Introducing polydispersity in equilibrium size and charge of microgels can greatly enrich bulk properties. Within a coarse-grained modeling framework [1-3], we derive effective electrostatic interactions in binary mixtures of ionic microgels that carry fixed charges on their surfaces. We model steric interactions between microgels via Hertz elastic pair potentials and swelling via Flory-Rehner theory of polymer networks. Inputting density-dependent effective interactions into Monte Carlo simulations, we compute equilibrium swelling ratios, radial distribution functions, and static structure factors of microgel solutions. We show that swelling behavior and structural properties are sensitive to polydispersity, expanding possibilities for controlling self-assembly and guiding design of novel materials.

[1] T. J. Weyer and A. R. Denton, Soft Matter 14, 4530 (2018).

[2] A. R. Denton and M. O. Alziyadi, J. Chem. Phys. 151, 074903 (2019).

[3] M. E. Brito, A. R. Denton, and G. Nägele, J. Chem. Phys. 151, 224901 (2019).