Field Responsive Swelling of Poly(Methacrylic Acid) Hydrogel-Isothermal Kinetic Analysis

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Externally controlled hydrogel swelling requires responsive materials and specific stimuli.
• Understanding swelling kinetics under various external fields is crucial for hydrogel applications.

Purpose of the Study:

• To investigate the influence of simultaneous ultrasound (US), microwave heating (MW), and cooling on poly(methacrylic acid) (PMAA) hydrogel swelling kinetics.
• To compare these effects with conventional thermal heating (TH).

Main Methods:

• Isothermal swelling kinetics of PMAA hydrogel were monitored from 248 K to 318 K.
• Simultaneous cooling was applied with US, MW, or TH.
• The Peppas model and a shrinking boundary surfaces model were used to analyze swelling kinetics.

Main Results:

• Microwave heating significantly accelerated PMAA hydrogel swelling (up to 48.8 times at 313 K).
• Different water penetration mechanisms were observed: non-Fickian diffusion under MW and Super-case II under TH and US.
• Swelling behavior was mathematically described using a shrinking boundary surfaces model.

Conclusions:

• External physical fields (US, MW) significantly influence the thermal activation and swelling behavior of PMAA xerogels.
• This research provides insights into field-responsive transport processes within hydrogel networks.