Electrostatic interactions reshape the internal architecture of ionic microgels

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Ionic co-monomers in polymer microgels influence swelling and pH-responsiveness.
• The impact of ionic groups on internal microgel structure is not well understood.

Purpose of the Study:

• To investigate how incorporating ionic groups affects the internal structure and swelling behavior of poly(N-isopropylacrylamide-co-acrylic acid) microgels.
• To elucidate the role of electrostatic interactions in modulating microgel architecture.

Main Methods:

• Dynamic and static light scattering (DLS/SLS)
• Small-angle X-ray scattering (SAXS)
• Monomer-resolved simulations

Main Results:

• Ionic microgels exhibit distinct form factors and swelling behavior compared to neutral counterparts.
• Simulations confirm that charge-induced network alterations are crucial for reproducing experimental results.
• Electrostatic interactions significantly modify the internal monomer density profile.

Conclusions:

• Ionic incorporation fundamentally alters microgel internal architecture beyond simple swelling changes.
• Electrostatic interactions are key drivers of structural organization in charged microgels.
• Current modeling approaches require extension to accurately capture the behavior of charged microgels.