Microion-Driven Free Swelling of Polyelectrolyte Cylindrical Microgel Shells

Polyelectrolyte cylindrical microgel shells are soft, stimuli-responsive colloids that exhibit distinctive swelling behavior governed by osmotic pressure. Understanding the osmotic pressure and swelling behavior of ionic microgels is essential for advancing their design and performance in applications such as tissue engineering and biosensing. In contrast to microcapsule microgels, cylindrical-shell microgels exhibit independent radial and axial swelling, governed by the balance between electrostatic and elastic contributions to their osmotic pressure. Using a cylindrical cell model and statistical-mechanical analysis within the Poisson–Boltzmann framework and molecular dynamics simulations, we compute the electrostatic contribution to the osmotic pressure. The gel contribution to the osmotic pressure is evaluated using the Flory-Rehner theory of swollen polymer networks. Increasing fixed-charge density, spread uniformly over the particle shell enhances cylindrical microgels swelling more in the axial than the radial direction. These findings provide a basis for designing anisotropic soft materials for biomedical and sensing applications.