Modeling ionic hydrogels swelling: characterization of the non-steady state

Area of Science:

• Materials Science
• Chemical Engineering
• Biomedical Engineering

Background:

• Ionic hydrogels are stimuli-responsive materials used in controlled release systems.
• Existing research often focuses on equilibrium swelling, neglecting the significant dynamic processes.
• pH-sensitive hydrogels, like poly(2-hydroxyethyl methacrylate-co-N, N-dimethylaminoethyl methacrylate) (poly(HEMA-co-DMAEMA)), are crucial for applications such as glucose-sensitive insulin delivery.

Purpose of the Study:

• To develop a mathematical compartmental model for understanding non-steady state swelling in pH-sensitive ionic hydrogels.
• To analyze the kinetic parameters governing the swelling behavior of poly(HEMA-co-DMAEMA).
• To facilitate the design and specification of stimuli-responsive hydrogel systems.

Main Methods:

• Development of a mathematical compartmental model using SAAM II software.
• Integration of experimental data with kinetic analysis.
• Investigation of factors influencing water uptake, including pH, amine group concentration, and crosslinking density.

Main Results:

• The rate of proton entry differs from the rate of water entry in poly(HEMA-co-DMAEMA) hydrogels.
• The water transport coefficient is dependent on external pH, incorporated amine groups, and polymer crosslinking density.
• Swelling equilibrium is achieved when all amine groups within the hydrogel become protonated.

Conclusions:

• A kinetic model can accurately predict the dynamic swelling behavior of pH-sensitive hydrogels.
• The model demonstrates predictive capability for both interpolated and extrapolated data, aiding future experimental design.
• Combining experimental and computational approaches is essential for overcoming complexities in hydrogel research and development.