Equilibrium swelling of multi-stimuli-responsive copolymer gels

Area of Science:

• Polymer Science
• Materials Science
• Biomedical Engineering

Background:

• Copolymer gels exhibit sensitivity to temperature, pH, and ionic strength.
• Biomedical applications require precise control over volume phase transition temperature (VPTT) and swelling.
• Existing copolymer gels fail to meet these requirements under alkaline or physiological saline conditions.

Purpose of the Study:

• To develop a model for predicting the equilibrium swelling of multi-stimuli-responsive copolymer gels.
• To account for secondary interactions like hydrogen bonding in the model.
• To optimize copolymer gel performance for controlled drug delivery.

Main Methods:

• Developed a model for equilibrium swelling of copolymer gels in aqueous solutions with varying pH and salt concentrations.
• Incorporated secondary interactions (hydrogen bonding) to describe hydrophobic segment aggregation kinetics.
• Determined material constants by fitting experimental swelling data for poly(N-isopropylacrylamide-co-sodium acrylate) gels.

Main Results:

• The model accurately predicts copolymer gel swelling behavior across different pH and salt conditions.
• Secondary interactions significantly influence hydrophobic segment aggregation above VPTT.
• Temperature, pH, and salt concentration effects on equilibrium swelling were numerically studied.

Conclusions:

• The developed model enhances the understanding and prediction of multi-stimuli-responsive copolymer gel behavior.
• This research provides a pathway for fine-tuning copolymer gels for advanced biomedical applications, particularly in drug delivery.
• The model's ability to account for secondary interactions offers a more comprehensive approach to copolymer gel design.