Charge-regularized swelling kinetics of polyelectrolyte gels: Elasticity and diffusion

Area of Science:

• Polymer Science
• Soft Matter Physics
• Physical Chemistry

Background:

• Polyelectrolyte (PE) gels are crucial in various applications, but their swelling behavior, especially under osmotic stress, requires precise modeling.
• Understanding the relationship between charge density, network elasticity, and swelling kinetics is essential for designing advanced materials.

Purpose of the Study:

• To develop and apply a new theoretical framework for modeling the swelling kinetics of spherical PE gels.
• To investigate the influence of polymer and charge densities, hydrophobicity, and network elasticity on gel swelling.
• To quantitatively determine the bulk modulus of PE gels and its dependence on charge density.

Main Methods:

• Utilized a recently developed phenomenological expression for osmotic stress.
• Employed numerical calculations based on the equation of motion for swelling kinetics.
• Compared theoretical predictions with experimental data for charged and uncharged minigels.

Main Results:

• The bulk modulus of PE gels decreases with increasing effective charge.
• Gel swelling rate increases with higher charge density, particularly under large deformations.
• Theoretical predictions for gel-front locations and size evolution closely matched experimental observations.

Conclusions:

• The developed theoretical model accurately captures the swelling behavior of PE gels, including large deformations.
• Experimental validation confirms that PE gel swelling is a diffusive process influenced by charge density.
• The study highlights the critical role of charge density in dictating PE gel mechanical properties and swelling dynamics.